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  • Box2D Difference Between WorldCenter and Position

    - by Free Lancer
    So this problem has been brothering for a couple of days now. First off, what is the difference between say Body.getWorldCenter() and Body.getPosition(). I heard that WorldCenter might have to do with the center of gravity or something. Second, When I create a Box2D Body for a sprite the Body is always at the lower left corner. I check it by printing a Rectangle of 1 pixel around the box.getWorldCenter(). From what I understand the Body should be in the center of the Sprite and its bounding box should wrap around the Sprite, correct? Here's an image of what I mean (The Sprite is Red, Body Blue): Here's some code: Body Creator: public static Body createBoxBody( final World pPhysicsWorld, final BodyType pBodyType, final FixtureDef pFixtureDef, Sprite pSprite ) { float pRotation = 0; float pCenterX = pSprite.getX() + pSprite.getWidth() / 2; float pCenterY = pSprite.getY() + pSprite.getHeight() / 2; float pWidth = pSprite.getWidth(); float pHeight = pSprite.getHeight(); final BodyDef boxBodyDef = new BodyDef(); boxBodyDef.type = pBodyType; //boxBodyDef.position.x = pCenterX / Constants.PIXEL_METER_RATIO; //boxBodyDef.position.y = pCenterY / Constants.PIXEL_METER_RATIO; boxBodyDef.position.x = pSprite.getX() / Constants.PIXEL_METER_RATIO; boxBodyDef.position.y = pSprite.getY() / Constants.PIXEL_METER_RATIO; Vector2 v = new Vector2( boxBodyDef.position.x * Constants.PIXEL_METER_RATIO, boxBodyDef.position.y * Constants.PIXEL_METER_RATIO ); Gdx.app.log("@Physics", "createBoxBody():: Box Position: " + v); // Temporary Box shape of the Body final PolygonShape boxPoly = new PolygonShape(); final float halfWidth = pWidth * 0.5f / Constants.PIXEL_METER_RATIO; final float halfHeight = pHeight * 0.5f / Constants.PIXEL_METER_RATIO; boxPoly.setAsBox( halfWidth, halfHeight ); // set the anchor point to be the center of the sprite pFixtureDef.shape = boxPoly; final Body boxBody = pPhysicsWorld.createBody(boxBodyDef); Gdx.app.log("@Physics", "createBoxBody():: Box Center: " + boxBody.getPosition().mul(Constants.PIXEL_METER_RATIO)); boxBody.createFixture(pFixtureDef); boxBody.setTransform( boxBody.getWorldCenter(), MathUtils.degreesToRadians * pRotation ); boxPoly.dispose(); return boxBody; } Making the Sprite: public Car( Texture texture, float pX, float pY, World world ) { super( "Car" ); mSprite = new Sprite( texture ); mSprite.setSize( mSprite.getWidth() / 6, mSprite.getHeight() / 6 ); mSprite.setPosition( pX, pY ); mSprite.setOrigin( mSprite.getWidth()/2, mSprite.getHeight()/2); FixtureDef carFixtureDef = new FixtureDef(); // Set the Fixture's properties, like friction, using the car's shape carFixtureDef.restitution = 1f; carFixtureDef.friction = 1f; carFixtureDef.density = 1f; // needed to rotate body using applyTorque mBody = Physics.createBoxBody( world, BodyDef.BodyType.DynamicBody, carFixtureDef, mSprite ); }

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  • I need help with specific types of movement.

    - by IronGiraffe
    I'm adding movable crates to my game and I need some help with my movement code. The way I've set up my movement code the crate's X and Y are moved according to a vector2 unless it hits a wall. Here's the movement code: if (frameCount % (delay / 2) == 0) { for (int i = 0; i < Math.Abs(cSpeed.X); i++) { if (!Level.PlayerHit(new Rectangle(crateBounds.X + (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height))) { if (!Level.CollideTiles(crateBounds.X + (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height)) { if (cSpeed.X != 0) { crateBounds.X += Math.Sign(cSpeed.X); } else { Equalize(2); } } else { cSpeed.X = 0f; } } else { if (!Level.CollideTiles(crateBounds.X - (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height)) { if (cSpeed.X != 0) { crateBounds.X -= Math.Sign(cSpeed.X); } else { Equalize(2); } } else { cSpeed.X = 0f; } } } for (int i = 0; i < Math.Abs(cSpeed.Y); i++) { if (!Level.PlayerHit(new Rectangle(crateBounds.X, crateBounds.Y + Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height))) { if (!Level.CollideTiles(crateBounds.X, crateBounds.Y + Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height)) { crateBounds.Y += Math.Sign(cSpeed.Y); } else { cSpeed.Y = 0f; } } else { if (!Level.CollideTiles(crateBounds.X, crateBounds.Y - Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height)) { crateBounds.Y -= Math.Sign(cSpeed.Y); } else { cSpeed.Y = 0f; } } } } The frameCount and delay variables just slow down the movement somewhat. Anyway, I've added a tool to my game that acts as a gravity well (drawing objects into it's center; the closer they get to the center the faster they go) and what I'm trying to do is make it so that the crate will bounce off the player (and vice versa) when they collide. Thus far, my code only keeps the crate and player from getting stuck inside each other (the player can still get stuck under the crate, but I'll fix that later.) So what I'd like to know is how I can best make the crate bounce off the player. The other movement problem I'm having is related to another tool which allows the player to pick up crates and move around with them. The problem is that the crate's movement while being carried isn't tied to the movement script (it moves the crate itself, instead of adding to speed), which makes the crate go through walls and such. I know what I have to do: make the crate's speed match the player's speed while the player is holding it, but I need the crate to snap to a certain position (just in front of the player) when the player grabs it and it needs to switch to another position (just in front of the player on the other side) when they player faces the other direction while holding it. What would be the best way to make it switch places while keeping all the movement tied to the speed vector?

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  • 3D collision physics. Response when hitting wall, floor or roof

    - by GlamCasvaluir
    I am having problem with the most basic physic response when the player collide with static wall, floor or roof. I have a simple 3D maze, true means solid while false means air: bool bMap[100][100][100]; The player is a sphere. I have keys for moving x++, x--, y++, y-- and diagonal at speed 0.1f (0.1 * ftime). The player can also jump. And there is gravity pulling the player down. Relative movement is saved in: relx, rely and relz. One solid cube on the map is exactly 1.0f width, height and depth. The problem I have is to adjust the player position when colliding with solids, I don't want it to bounce or anything like that, just stop. But if moving diagonal left/up and hitting solid up, the player should continue moving left, sliding along the wall. Before moving the player I save the old player position: oxpos = xpos; oypos = ypos; ozpos = zpos; vec3 direction; direction = vec3(relx, rely, relz); xpos += direction.x*ftime; ypos += direction.y*ftime; zpos += direction.z*ftime; gx = floor(xpos+0.25); gy = floor(ypos+0.25); gz = floor(zpos+0.25); if (bMap[gx][gy][gz] == true) { vec3 normal = vec3(0.0, 0.0, 1.0); // <- Problem. vec3 invNormal = vec3(-normal.x, -normal.y, -normal.z) * length(direction * normal); vec3 wallDir = direction - invNormal; xpos = oxpos + wallDir.x; ypos = oypos + wallDir.y; zpos = ozpos + wallDir.z; } The problem with my version is that I do not know how to chose the correct normal for the cube side. I only have the bool array to look at, nothing else. One theory I have is to use old values of gx, gy and gz, but I do not know have to use them to calculate the correct cube side normal.

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  • Physics Engine [Collision Response, 2-dimensional] experts, help!! My stack is unstable!

    - by Register Sole
    Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based method with Projected-Gauss-Seidel (PGS) iterative solver as described by Erin Catto (mentioned in the reference of the paper as [Catt05]). So here's how it currently is: The simulation handles 2-dimensional rotating convex polygons. Detection is using separating-axis test, with a SKIN, meaning closest points between two polygons is detected and determined if their distance is less than SKIN. To resolve collision, simultaneous impulse-based method is used. It is solved using iterative solver (PGS-solver) as in Erin Catto's paper. Error-correction is implemented using Baumgarte's stabilization (you can refer to either paper for this) using J V = beta/dt*overlap, J is the Jacobian for the constraints, V the matrix containing the velocities of the bodies, beta an error-correction parameter that is better be < 1, dt the time-step taken by the engine, and overlap, the overlap between the bodies (true overlap, so SKIN is ignored). However, it is still less stable than I expected :s I tried to stack hexagons (or squares, doesn't really matter), and even with only 4 to 5 of them, they hardly stand still! Also note that I am not looking for a sleeping scheme. But I would settle if you have any explicit scheme to handle resting contacts. That said, I would be more than happy if you have a way of treating it generally (as continuous collision, instead of explicitly as a special state). Ideas I have: I would try adding a damping term (proportional to velocity) to the Baumgarte. Is this a good idea in general? If not I would not want to waste my time trying to tune the parameter hoping it magically works. Ideas I have tried: Using simultaneous position based error correction as described in the paper in section 5.3.2, turned out to be worse than the current scheme. If you want to know the parameters I used: Hexagons, side 50 (pixels) gravity 2400 (pixels/sec^2) time-step 1/60 (sec) beta 0.1 restitution 0 to 0.2 coeff. of friction 0.2 PGS iteration 10 initial separation 10 (pixels) mass 1 (unit is irrelevant for now, i modified velocity directly<-impulse method) inertia 1/1000 Thanks in advance! I really appreciate any help from you guys!! :)

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  • Programming an Android Button to update EditText views

    - by bergler77
    Ok guys, I have a button in android that i'm trying to use to update 8 EditText Views with different random numbers. Everything works up until I click the button. It appears I am missing a resource according to the debugger, but I'm not sure what. I've tried several different ways of implementing the button. Here is what I have after looking at several posts. import java.util.Random; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; public class MyCharNewChar extends MyCharActivity { private OnClickListener randomButtonListener = new OnClickListener(){ public void onClick(View v) { //Button creates a set of random numbers and updates the values //of the EditText views. Random rand = new Random(); int STR = 1 + rand.nextInt(12); int AGI = 1 + rand.nextInt(12); int DEX = 1 + rand.nextInt(12); int WIS = 1 + rand.nextInt(12); int INT = 1 + rand.nextInt(12); int CON = 1 + rand.nextInt(12); int HP = 1 + rand.nextInt(20); int AC = 1 + rand.nextInt(6); EditText str = (EditText) findViewById(R.id.str); str.setText(STR); EditText agi = (EditText) findViewById(R.id.agi); agi.setText(AGI); EditText dex = (EditText) findViewById(R.id.dex); dex.setText(DEX); EditText wis = (EditText) findViewById(R.id.wis); wis.setText(WIS); EditText intel = (EditText) findViewById(R.id.intel); intel.setText(INT); EditText con = (EditText) findViewById(R.id.con); con.setText(CON); EditText hp = (EditText) findViewById(R.id.baseHP); hp.setText(HP); EditText ac = (EditText) findViewById(R.id.baseAC); ac.setText(AC); } }; @Override public void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); setContentView(R.layout.newchar); Button randomButton = (Button) findViewById(R.id.randomButton); randomButton.setOnClickListener(randomButtonListener); } } Here is the xml: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/linearlayoutNew1" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:background="@drawable/background" > <TextView android:id="@+id/newCharLabel" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="@string/new_character_screen" android:textSize="24dp" android:textColor="@color/splash" android:textStyle="bold" android:gravity="center"/> <TextView android:id="@+id/nameLabel" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="@string/nameLabel" android:textSize="18dp" android:textColor="@color/splash"/> <EditText android:id="@+id/editText1" android:layout_width="match_parent" android:layout_height="wrap_content" android:ems="10" android:inputType="textPersonName" > <requestFocus /> </EditText> <TableLayout android:id="@+id/statsLayout" android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="5dp"> <TableRow android:id="@+id/tableRow01" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="5dp"> <TextView android:id="@+id/strLabel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/strLabel" android:textSize="18dp" android:textColor="@color/splash"/> <EditText android:id="@+id/str" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="3" android:inputType="number" /> <TextView android:id="@+id/agiLabel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/agiLabel" android:textSize="18dp" android:textColor="@color/splash"/> <EditText android:id="@+id/agi" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="3" android:inputType="number"/> <TextView android:id="@+id/dexLabel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/dexLabel" android:textSize="18dp" android:textColor="@color/splash"/> <EditText android:id="@+id/dex" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="3" android:inputType="number"/> </TableRow> <TableRow android:id="@+id/tableRow02" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="5dp"> <TextView android:id="@+id/intLabel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/intLabel" android:textSize="18dp" android:textColor="@color/splash"/> <EditText android:id="@+id/intel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="3" android:inputType="number"/> <TextView android:id="@+id/wisLabel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/wisLabel" android:textSize="18dp" android:textColor="@color/splash"/> <EditText android:id="@+id/wis" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="3" android:inputType="number"/> <TextView android:id="@+id/conLabel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/conLabel" android:textSize="18dp" android:textColor="@color/splash"/> <EditText android:id="@+id/con" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="3" android:inputType="number"/> </TableRow> </TableLayout> <LinearLayout android:id="@+id/linearlayoutNew02" android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="5dp" android:gravity="center"> <TextView android:id="@+id/baseHPLabel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/hpLabel" android:textSize="18dp" android:textColor="@color/splash"/> <EditText android:id="@+id/baseHP" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="3" android:inputType="number"/> <TextView android:id="@+id/baseACLabel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/acLabel" android:textSize="18dp" android:textColor="@color/splash"/> <EditText android:id="@+id/baseAC" android:layout_width="wrap_content" android:layout_height="wrap_content" android:ems="3" android:inputType="number"/> </LinearLayout> <LinearLayout android:id="@+id/linearlayoutNew03" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal"> <Button android:id="@+id/randomButton" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="@string/randomButton" android:textSize="16dp" android:clickable="true"/> </LinearLayout> </LinearLayout> I have also tried setting the onClick in xml to setup a specific onClick method. Still the same error so I must have a problem elsewhere. Any suggestions would be great!

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  • Android Uncaught Exception

    - by Agrim Asthana
    09-30 02:32:31.474: D/ddm-heap(214): Got feature list request 09-30 02:32:31.634: D/AndroidRuntime(214): Shutting down VM 09-30 02:32:31.634: W/dalvikvm(214): threadid=3: thread exiting with uncaught exception (group=0x4001b188) 09-30 02:32:31.634: E/AndroidRuntime(214): Uncaught handler: thread main exiting due to uncaught exception 09-30 02:32:31.654: E/AndroidRuntime(214): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.mjcet.mjcet/com.mjcet.mjcet.MJCET}: java.lang.ClassNotFoundException: com.mjcet.mjcet.MJCET in loader dalvik.system.PathClassLoader@44e8c820 09-30 02:32:31.654: E/AndroidRuntime(214): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2417) 09-30 02:32:31.654: E/AndroidRuntime(214): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512) 09-30 02:32:31.654: E/AndroidRuntime(214): at android.app.ActivityThread.access$2200(ActivityThread.java:119) 09-30 02:32:31.654: E/AndroidRuntime(214): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863) 09-30 02:32:31.654: E/AndroidRuntime(214): at android.os.Handler.dispatchMessage(Handler.java:99) 09-30 02:32:31.654: E/AndroidRuntime(214): at android.os.Looper.loop(Looper.java:123) 09-30 02:32:31.654: E/AndroidRuntime(214): at android.app.ActivityThread.main(ActivityThread.java:4363) 09-30 02:32:31.654: E/AndroidRuntime(214): at java.lang.reflect.Method.invokeNative(Native Method) 09-30 02:32:31.654: E/AndroidRuntime(214): at java.lang.reflect.Method.invoke(Method.java:521) 09-30 02:32:31.654: E/AndroidRuntime(214): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 09-30 02:32:31.654: E/AndroidRuntime(214): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 09-30 02:32:31.654: E/AndroidRuntime(214): at dalvik.system.NativeStart.main(Native Method) 09-30 02:32:31.654: E/AndroidRuntime(214): Caused by: java.lang.ClassNotFoundException: com.mjcet.mjcet.MJCET in loader dalvik.system.PathClassLoader@44e8c820 09-30 02:32:31.654: E/AndroidRuntime(214): at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:243) 09-30 02:32:31.654: E/AndroidRuntime(214): at java.lang.ClassLoader.loadClass(ClassLoader.java:573) 09-30 02:32:31.654: E/AndroidRuntime(214): at java.lang.ClassLoader.loadClass(ClassLoader.java:532) 09-30 02:32:31.654: E/AndroidRuntime(214): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 09-30 02:32:31.654: E/AndroidRuntime(214): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2409) 09-30 02:32:31.654: E/AndroidRuntime(214): ... 11 more 09-30 02:32:31.684: I/dalvikvm(214): threadid=7: reacting to signal 3 09-30 02:32:31.684: E/dalvikvm(214): Unable to open stack trace file '/data/anr/traces.txt': Permission denied the above is my debugging output for the below activities LOGINACTIVITY.java package com.agrim.mjcet; import com.agrim.mjcet.R; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.view.View; //import android.widget.TextView; import android.widget.Button; import android.widget.EditText; import android.view.View.OnClickListener; public class LoginActivity extends Activity { EditText txtUserName; EditText txtPassword; Button btnLogin; Button btnCancel; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // setting default screen to login.xml setContentView(R.layout.main); txtUserName=(EditText)this.findViewById(R.id.txtUname); txtPassword=(EditText)this.findViewById(R.id.txtPwd); btnLogin=(Button)this.findViewById(R.id.btnLogin); btnLogin=(Button)this.findViewById(R.id.btnLogin); btnLogin.setOnClickListener(new OnClickListener() { public void onClick(View v) { // Switching to Register screen if((txtUserName.getText().toString()).equals(txtPassword.getText().toString())) { Intent myIntent = new Intent(getApplicationContext(),SampleActivity.class); startActivityForResult(myIntent, 0); } } } ); } } SAMPLE ACTIVITY.java package com.agrim.mjcet; import com.agrim.mjcet.R; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.TextView; public class SampleActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Set View to register.xml setContentView(R.layout.lol); TextView HomeScreen = (TextView) findViewById(R.id.back); HomeScreen.setOnClickListener(new View.OnClickListener() { public void onClick(View arg0) { // Closing registration screen // Switching to Login Screen/closing register screen finish(); } }); } } and here are my 2 layouts MAIN.XML <TableLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="#000000" android:stretchColumns="1"> <TableRow> <TextView android:text="@string/user_name" android:textColor="#347235" android:id="@+id/TextView01" android:layout_width="wrap_content" android:layout_marginLeft="25dip" android:layout_height="wrap_content"> </TextView> <EditText android:text="" android:inputType="text" android:id="@+id/txtUname" android:layout_weight="0.75" android:layout_width="wrap_content" android:layout_marginRight="10dip" android:layout_marginBottom="5dip" android:background="#FFFFFF" android:layout_height="wrap_content"> </EditText> </TableRow> <TableRow> <TextView android:text="@string/password" android:textColor="#347235" android:id="@+id/TextView02" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginLeft="25dip"> </TextView> <EditText android:text="" android:inputType="textPassword" android:id="@+id/txtPwd" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginRight="10dip" android:layout_weight="1" android:background="#FFFFFF" android:gravity="center"> </EditText> </TableRow> <TableRow> <Button android:id="@+id/btnLogin" android:layout_width="fill_parent" android:layout_height="wrap_content" android:background="#FFFFFF" android:layout_marginTop="25dip" android:layout_marginLeft="50dip" android:onClick="onClickMyButton" android:text="@string/login" /> <Button android:id="@+id/btnCancel" android:layout_width="fill_parent" android:layout_height="wrap_content" android:background="#FFFFFF" android:layout_marginTop="25dip" android:layout_marginLeft="100dip" android:layout_marginRight="50dip" android:text="@string/cancel" /> </TableRow> <FrameLayout android:layout_width="wrap_content" android:layout_height="match_parent" > <ImageView android:layout_width="fill_parent" android:layout_height="match_parent" android:scaleType="centerInside" android:src="@drawable/logo_invert" android:contentDescription="@drawable/logo_invert"/> </FrameLayout> </TableLayout> and finally LOL.xml <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:background="#000000" android:layout_height="fill_parent" > <ImageView android:layout_width="fill_parent" android:id="@+id/back" android:layout_height="match_parent" android:scaleType="centerInside" android:src="@drawable/lol" android:contentDescription="@drawable/lol"> </ImageView> <RelativeLayout android:layout_width="match_parent" android:layout_height="138dp" android:orientation="vertical" android:gravity="bottom" > <TextView android:id="@+id/TextView02" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_centerHorizontal="true" android:text="@string/coming_soon" android:textColor="#347235" /> </RelativeLayout> </FrameLayout> I get a force close upon initialization.. and yes this is my first android app :)

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  • simple collision detection with box2dweb

    - by skywalker
    im beginner in box2dweb that version of box2d for javascript i wrote simple gravity system and i want to detect the collision between the box and the ground , when the falling box hit the ground execute simple function like function sucs(){alert("the box on the floor !")}; this is my code var CANVAS_WIDTH = 1024, CANVAS_HEIGHT = 700, SCALE = 30; var b2Vec2 = Box2D.Common.Math.b2Vec2 , b2BodyDef = Box2D.Dynamics.b2BodyDef , b2Body = Box2D.Dynamics.b2Body , b2FixtureDef = Box2D.Dynamics.b2FixtureDef , b2Fixture = Box2D.Dynamics.b2Fixture , b2World = Box2D.Dynamics.b2World , b2MassData = Box2D.Collision.Shapes.b2MassData , b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape , b2CircleShape = Box2D.Collision.Shapes.b2CircleShape , b2DebugDraw = Box2D.Dynamics.b2DebugDraw; var canvas = document.getElementById("canvas"); var context = canvas.getContext("2d"); var world = new b2World(new b2Vec2(0, 8), true); var fixDef = new b2FixtureDef(); var bodyDef = new b2BodyDef(); fixDef.density = 1.0; fixDef.friction = 0.5; bodyDef.type = b2Body.b2_staticBody; fixDef.shape = new b2PolygonShape; fixDef.shape.SetAsBox(20, 2); bodyDef.position.Set(10, 400 / 30 + 1.8); world.CreateBody(bodyDef).CreateFixture(fixDef); fixDef.density = 1.0; fixDef.friction = 0.5; fixDef.restitution = 0.3; bodyDef.type = b2Body.b2_dynamicBody; bodyDef.position.Set(50 / SCALE, 0 / SCALE); //bodyDef.linearVelocity.Set((Math.random() * 12) + 2, (Math.random() * 12) + 2); fixDef.shape = new b2PolygonShape(); fixDef.shape.SetAsBox(25 / SCALE, 25 / SCALE); world.CreateBody(bodyDef).CreateFixture(fixDef); var debugDraw = new b2DebugDraw(); debugDraw.SetSprite(document.getElementById("canvas").getContext("2d")); debugDraw.SetDrawScale(30.0); debugDraw.SetFillAlpha(0.5); debugDraw.SetLineThickness(1.0); debugDraw.SetFlags(b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit); world.SetDebugDraw(debugDraw); var image = new Image(); image.src = "image.png"; window.setInterval(gameLoop, 1000 / 60); function gameLoop() { world.Step(1 / 60, 8, 3); world.ClearForces(); context.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT); b = world.GetBodyList() var pos = b.GetPosition(); context.save(); context.translate(pos.x * SCALE, pos.y * SCALE); context.rotate(b.GetAngle()); context.drawImage(image, -25, -25); context.restore(); b = b.GetNext(); pos = b.GetPosition(); context.save(); context.translate(pos.x * SCALE, pos.y * SCALE); //b.GetAngle()++; context.rotate(b.GetAngle()); context.drawImage(image, -25, -25); context.restore(); world.DrawDebugData(); };

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  • Algorithm to Find the Aggregate Mass of "Granola Bar"-Like Structures?

    - by Stuart Robbins
    I'm a planetary science researcher and one project I'm working on is N-body simulations of Saturn's rings. The goal of this particular study is to watch as particles clump together under their own self-gravity and measure the aggregate mass of the clumps versus the mean velocity of all particles in the cell. We're trying to figure out if this can explain some observations made by the Cassini spacecraft during the Saturnian summer solstice when large structures were seen casting shadows on the nearly edge-on rings. Below is a screenshot of what any given timestep looks like. (Each particle is 2 m in diameter and the simulation cell itself is around 700 m across.) The code I'm using already spits out the mean velocity at every timestep. What I need to do is figure out a way to determine the mass of particles in the clumps and NOT the stray particles between them. I know every particle's position, mass, size, etc., but I don't know easily that, say, particles 30,000-40,000 along with 102,000-105,000 make up one strand that to the human eye is obvious. So, the algorithm I need to write would need to be a code with as few user-entered parameters as possible (for replicability and objectivity) that would go through all the particle positions, figure out what particles belong to clumps, and then calculate the mass. It would be great if it could do it for "each" clump/strand as opposed to everything over the cell, but I don't think I actually need it to separate them out. The only thing I was thinking of was doing some sort of N2 distance calculation where I'd calculate the distance between every particle and if, say, the closest 100 particles were within a certain distance, then that particle would be considered part of a cluster. But that seems pretty sloppy and I was hoping that you CS folks and programmers might know of a more elegant solution? Edited with My Solution: What I did was to take a sort of nearest-neighbor / cluster approach and do the quick-n-dirty N2 implementation first. So, take every particle, calculate distance to all other particles, and the threshold for in a cluster or not was whether there were N particles within d distance (two parameters that have to be set a priori, unfortunately, but as was said by some responses/comments, I wasn't going to get away with not having some of those). I then sped it up by not sorting distances but simply doing an order N search and increment a counter for the particles within d, and that sped stuff up by a factor of 6. Then I added a "stupid programmer's tree" (because I know next to nothing about tree codes). I divide up the simulation cell into a set number of grids (best results when grid size ˜7 d) where the main grid lines up with the cell, one grid is offset by half in x and y, and the other two are offset by 1/4 in ±x and ±y. The code then divides particles into the grids, then each particle N only has to have distances calculated to the other particles in that cell. Theoretically, if this were a real tree, I should get order N*log(N) as opposed to N2 speeds. I got somewhere between the two, where for a 50,000-particle sub-set I got a 17x increase in speed, and for a 150,000-particle cell, I got a 38x increase in speed. 12 seconds for the first, 53 seconds for the second, 460 seconds for a 500,000-particle cell. Those are comparable speeds to how long the code takes to run the simulation 1 timestep forward, so that's reasonable at this point. Oh -- and it's fully threaded, so it'll take as many processors as I can throw at it.

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  • Create bullet physics rigid body along the vertices of a blender model

    - by Krishnabhadra
    I am working on my first 3D game, for iphone, and I am using Blender to create models, Cocos3D game engine and Bullet for physics simulation. I am trying to learn the use of physics engine. What I have done I have created a small model in blender which contains a Cube (default blender cube) at the origin and a UVSphere hovering exactly on top of this cube (without touching the cube) I saved the file to get MyModel.blend. Then I used File -> Export -> PVRGeoPOD (.pod/.h/.cpp) in Blender to export the model to .pod format to use along with Cocos3D. In the coding side, I added necessary bullet files to my Cocos3D template project in XCode. I am also using a bullet objective C wrapper. -(void) initializeScene { _physicsWorld = [[CC3PhysicsWorld alloc] init]; [_physicsWorld setGravity:0 y:-9.8 z:0]; /*Setup camera, lamp etc.*/ .......... ........... /*Add models created in blender to scene*/ [self addContentFromPODFile: @"MyModel.pod"]; /*Create OpenGL ES buffers*/ [self createGLBuffers]; /*get models*/ CC3MeshNode* cubeNode = (CC3MeshNode*)[self getNodeNamed:@"Cube"]; CC3MeshNode* sphereNode = (CC3MeshNode*)[self getNodeNamed:@"Sphere"]; /*Those boring grey colors..*/ [cubeNode setColor:ccc3(255, 255, 0)]; [sphereNode setColor:ccc3(255, 0, 0)]; float *cVertexData = (float*)((CC3VertexArrayMesh*)cubeNode.mesh).vertexLocations.vertices; int cVertexCount = (CC3VertexArrayMesh*)cubeNode.mesh).vertexLocations.vertexCount; btTriangleMesh* cTriangleMesh = new btTriangleMesh(); // for (int i = 0; i < cVertexCount * 3; i+=3) { // printf("\n%f", cVertexData[i]); // printf("\n%f", cVertexData[i+1]); // printf("\n%f", cVertexData[i+2]); // } /*Trying to create a triangle mesh that curresponds the cube in 3D space.*/ int offset = 0; for (int i = 0; i < (cVertexCount / 3); i++){ unsigned int index1 = offset; unsigned int index2 = offset+6; unsigned int index3 = offset+12; cTriangleMesh->addTriangle( btVector3(cVertexData[index1], cVertexData[index1+1], cVertexData[index1+2] ), btVector3(cVertexData[index2], cVertexData[index2+1], cVertexData[index2+2] ), btVector3(cVertexData[index3], cVertexData[index3+1], cVertexData[index3+2] )); offset += 18; } [self releaseRedundantData]; /*Create a collision shape from triangle mesh*/ btBvhTriangleMeshShape* cTriMeshShape = new btBvhTriangleMeshShape(cTriangleMesh,true); btCollisionShape *sphereShape = new btSphereShape(1); /*Create physics objects*/ gTriMeshObject = [_physicsWorld createPhysicsObjectTrimesh:cubeNode shape:cTriMeshShape mass:0 restitution:1.0 position:cubeNode.location]; sphereObject = [_physicsWorld createPhysicsObject:sphereNode shape:sphereShape mass:1 restitution:0.1 position:sphereNode.location]; sphereObject.rigidBody->setDamping(0.1,0.8); } When I run the sphere and cube shows up fine. I expect the sphere object to fall directly on top of the cube, since I have given it a mass of 1 and the physics world gravity is given as -9.8 in y direction. But What is happening the spere rotates around cube three or times and then just jumps out of the scene. Then I know I have some basic misunderstanding about the whole process. So my question is, how can I create a physics collision shape which corresponds to the shape of a particular mesh model. I may need complex shapes than cube and sphere, but before going into them I want to understand the concepts.

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  • Flash Actionscript 3.0 Game Projectile Creation

    - by Christian Basar
    I have been creating a side-scrolling Actionscript 3.0 game. In this game I want the Player to be able to shoot blow darts as weapons. I had some trouble getting the darts to be created in the right place (in front of the player), but eventually got it working with some help from this page (please look at it for background information on this problem): http://stackoverflow.com/questions/8031553/flash-actionscript-3-0-game-projectile-creation I got the darts to be created in the right place (near the player) and a 'movePlayerDarts()' function moves them. But I actually have a new problem. When the player moves after firing a dart, the dart tries to follow him! If the player jumps, the dart rises up. If the player moves to the left, the dart moves slightly to the left. Obviously, there is some code somewhere which is telling the darts to follow the player. I do not see how, unless the 'playerDartContainer' has something to do with that. But the container is always at position (0,0) and it does not move. Also, as a test I traced a dart's 'y' coordinate within the constantly-running 'movePlayerDarts()' function. As you can see, that function constantly moves the dart down the y axis by increasing its y-coordinate value. But when I jump, the 'y' coordinate being traced is never reduced, even though the dart clearly looks like it's rising! If anybody has any suggestions, I'd appreciate them! Here is the code I use to create the darts: // This function creates a dart public function createDart():void { if (playerDartContainer.numChildren <= 4) { // Play dart shooting sound sndDartShootIns.play(); // Create a new 'PlayerDart' object playerDart = new PlayerDart(); // Set the new dart's initial position and direction depending on the player's direction // Player's facing right if (player.scaleX == 1) { // Create dart in front of player's dart gun playerDart.x = player.x + 12; playerDart.y = player.y - 85; // Dart faces right, too playerDart.scaleX = 1; } // Player's facing left else if (player.scaleX == -1) { // Create dart in front of player's dart gun playerDart.x = player.x - 12; playerDart.y = player.y - 85; // Dart faces left, too playerDart.scaleX = -1; } playerDartContainer.addChild(playerDart); } } // End of 'createDart()' function This code is the EnterFrameHandler for the player darts: // In every frame, call 'movePlayerDarts()' to move the darts within the 'playerDartContainer' public function playerDartEnterFrameHandler(event:Event):void { // Only move the Player's darts if their container has at least one dart within if (playerDartContainer.numChildren > 0) { movePlayerDarts(); } } And finally, this is the code that actually moves all of the player's darts: // Move all of the Player's darts public function movePlayerDarts():void { for (var pdIns:int = 0; pdIns < playerDartContainer.numChildren; pdIns++) { // Set the Player Dart 'instance' variable to equal the current PlayerDart playerDartIns = PlayerDart(playerDartContainer.getChildAt(pdIns)); // Move the current dart in the direction it was shot. The dart's 'x-scale' // factor is multiplied by its speed (5) to move the dart in its correct // direction. If the 'x-scale' factor is -1, the dart is pointing left (as // seen in the 'createDart()' function. (-1 * 5 = -5), so the dart will go // to left at a rate of 5. The opposite is true for the right-ward facing // darts playerDartIns.x += playerDartIns.scaleX * 1; // Make gravity work on the dart playerDartIns.y += 0.7; //playerDartIns.y += 1; // What if the dart hits the ground? if (HitTest.intersects(playerDartIns, floor, this)) { playerDartContainer.removeChild(playerDartIns); } //trace("Dart x: " + playerDartIns.x); trace("Dart y: " + playerDartIns.y); } }

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  • Move a sphere along the swipe?

    - by gameOne
    I am trying to get a sphere curl based on the swipe. I know this has been asked many times, but still it's yearning to be answered. I have managed to add force on the direction of the swipe and it works near perfect. I also have all the swipe positions stored in a list. Now I would like to know how can the curl be achieved. I believe the the curve in the swipe can be calculated by the Vector dot product If theta is 0, then there is no need to add the swipe. If it is not, then add the curl. Maybe this condition is redundant if I managed to find how to curl the sphere along the swipe position The code that adds the force to sphere based on the swipe direction is as below: using UnityEngine; using System.Collections; using System.Collections.Generic; public class SwipeControl : MonoBehaviour { //First establish some variables private Vector3 fp; //First finger position private Vector3 lp; //Last finger position private Vector3 ip; //some intermediate finger position private float dragDistance; //Distance needed for a swipe to register public float power; private Vector3 footballPos; private bool canShoot = true; private float factor = 40f; private List<Vector3> touchPositions = new List<Vector3>(); void Start(){ dragDistance = Screen.height*20/100; Physics.gravity = new Vector3(0, -20, 0); footballPos = transform.position; } // Update is called once per frame void Update() { //Examine the touch inputs foreach (Touch touch in Input.touches) { /*if (touch.phase == TouchPhase.Began) { fp = touch.position; lp = touch.position; }*/ if (touch.phase == TouchPhase.Moved) { touchPositions.Add(touch.position); } if (touch.phase == TouchPhase.Ended) { fp = touchPositions[0]; lp = touchPositions[touchPositions.Count-1]; ip = touchPositions[touchPositions.Count/2]; //First check if it's actually a drag if (Mathf.Abs(lp.x - fp.x) > dragDistance || Mathf.Abs(lp.y - fp.y) > dragDistance) { //It's a drag //Now check what direction the drag was //First check which axis if (Mathf.Abs(lp.x - fp.x) > Mathf.Abs(lp.y - fp.y)) { //If the horizontal movement is greater than the vertical movement... if ((lp.x>fp.x) && canShoot) //If the movement was to the right) { //Right move float x = (lp.x - fp.x) / Screen.height * factor; rigidbody.AddForce((new Vector3(x,10,16))*power); Debug.Log("right "+(lp.x-fp.x));//MOVE RIGHT CODE HERE canShoot = false; //rigidbody.AddForce((new Vector3((lp.x-fp.x)/30,10,16))*power); StartCoroutine(ReturnBall()); } else { //Left move float x = (lp.x - fp.x) / Screen.height * factor; rigidbody.AddForce((new Vector3(x,10,16))*power); Debug.Log("left "+(lp.x-fp.x));//MOVE LEFT CODE HERE canShoot = false; //rigidbody.AddForce(new Vector3((lp.x-fp.x)/30,10,16)*power); StartCoroutine(ReturnBall()); } } else { //the vertical movement is greater than the horizontal movement if (lp.y>fp.y) //If the movement was up { //Up move float y = (lp.y-fp.y)/Screen.height*factor; float x = (lp.x - fp.x) / Screen.height * factor; rigidbody.AddForce((new Vector3(x,y,16))*power); Debug.Log("up "+(lp.x-fp.x));//MOVE UP CODE HERE canShoot = false; //rigidbody.AddForce(new Vector3((lp.x-fp.x)/30,10,16)*power); StartCoroutine(ReturnBall()); } else { //Down move Debug.Log("down "+lp+" "+fp);//MOVE DOWN CODE HERE } } } else { //It's a tap Debug.Log("none");//TAP CODE HERE } } } } IEnumerator ReturnBall() { yield return new WaitForSeconds(5.0f); rigidbody.velocity = Vector3.zero; rigidbody.angularVelocity = Vector3.zero; transform.position = footballPos; canShoot =true; isKicked = false; } }

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  • Platform jumping problems with AABB collisions

    - by Vee
    See the diagram first: When my AABB physics engine resolves an intersection, it does so by finding the axis where the penetration is smaller, then "push out" the entity on that axis. Considering the "jumping moving left" example: If velocityX is bigger than velocityY, AABB pushes the entity out on the Y axis, effectively stopping the jump (result: the player stops in mid-air). If velocityX is smaller than velocitY (not shown in diagram), the program works as intended, because AABB pushes the entity out on the X axis. How can I solve this problem? Source code: public void Update() { Position += Velocity; Velocity += World.Gravity; List<SSSPBody> toCheck = World.SpatialHash.GetNearbyItems(this); for (int i = 0; i < toCheck.Count; i++) { SSSPBody body = toCheck[i]; body.Test.Color = Color.White; if (body != this && body.Static) { float left = (body.CornerMin.X - CornerMax.X); float right = (body.CornerMax.X - CornerMin.X); float top = (body.CornerMin.Y - CornerMax.Y); float bottom = (body.CornerMax.Y - CornerMin.Y); if (SSSPUtils.AABBIsOverlapping(this, body)) { body.Test.Color = Color.Yellow; Vector2 overlapVector = SSSPUtils.AABBGetOverlapVector(left, right, top, bottom); Position += overlapVector; } if (SSSPUtils.AABBIsCollidingTop(this, body)) { if ((Position.X >= body.CornerMin.X && Position.X <= body.CornerMax.X) && (Position.Y + Height/2f == body.Position.Y - body.Height/2f)) { body.Test.Color = Color.Red; Velocity = new Vector2(Velocity.X, 0); } } } } } public static bool AABBIsOverlapping(SSSPBody mBody1, SSSPBody mBody2) { if(mBody1.CornerMax.X <= mBody2.CornerMin.X || mBody1.CornerMin.X >= mBody2.CornerMax.X) return false; if (mBody1.CornerMax.Y <= mBody2.CornerMin.Y || mBody1.CornerMin.Y >= mBody2.CornerMax.Y) return false; return true; } public static bool AABBIsColliding(SSSPBody mBody1, SSSPBody mBody2) { if (mBody1.CornerMax.X < mBody2.CornerMin.X || mBody1.CornerMin.X > mBody2.CornerMax.X) return false; if (mBody1.CornerMax.Y < mBody2.CornerMin.Y || mBody1.CornerMin.Y > mBody2.CornerMax.Y) return false; return true; } public static bool AABBIsCollidingTop(SSSPBody mBody1, SSSPBody mBody2) { if (mBody1.CornerMax.X < mBody2.CornerMin.X || mBody1.CornerMin.X > mBody2.CornerMax.X) return false; if (mBody1.CornerMax.Y < mBody2.CornerMin.Y || mBody1.CornerMin.Y > mBody2.CornerMax.Y) return false; if(mBody1.CornerMax.Y == mBody2.CornerMin.Y) return true; return false; } public static Vector2 AABBGetOverlapVector(float mLeft, float mRight, float mTop, float mBottom) { Vector2 result = new Vector2(0, 0); if ((mLeft > 0 || mRight < 0) || (mTop > 0 || mBottom < 0)) return result; if (Math.Abs(mLeft) < mRight) result.X = mLeft; else result.X = mRight; if (Math.Abs(mTop) < mBottom) result.Y = mTop; else result.Y = mBottom; if (Math.Abs(result.X) < Math.Abs(result.Y)) result.Y = 0; else result.X = 0; return result; }

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  • how to keep display tick rate steady when using continuous collision detection?

    - by nas Ns
    (I've just found about this forum). I hope it is ok to repost my question again here. I posted this question at stackoverflow, but it looks like I might get better help here. Here is the question: I've implemented basic particles motion simulation with continuous collision detection. But there is small issue in display. Assume simple case of circles moving inside square. All elastic collisions. no firction. All motion is constant speed. No forces are involved, no gravity. So when a particle is moving, it is always moving at constant speed (in between collisions) What I do now is this: Let the simulation time step be 1 second (for example). This is the time step simulation is advanced before displaying the new state (unless there is a collision sooner than this). At start of each time step, time for the next collision between any particles or a particle with a wall is determined. Call this the TOC time; let’s say TOC was .5 seconds in this case. Since TOC is smaller than the standard time step, then the system is moved by TOC and the new system is displayed so that the new display shows any collisions as just taking place (say 2 circles just touched each other’s, or a circle just touched a wall) Next, the collision(s) are resolved (i.e. speeds updated, changed directions etc..). A new step is started. The same thing happens. Now assume there is no collision detected within the next 1 second (those 2 circles above will not be in collision any more, even though they are still touching, due to their speeds showing they are moving apart now), Hence, simulation time is advanced now by the full one second, the standard time step, and particles are moved on the screen using 1 second simulation time and new display is shown. You see what has just happened: One frame ran for .5 seconds, but the next frame runs for 1 second, may be the 3rd frame is displayed after 2 seconds, may be the 4th frame is displayed after 2.8 seconds (because TOC was .8 seconds then) and so on. What happens is that the motion of a particle on the screen appears to speed up or slow down, even though it is moving at constant speed and was not even involved in a collision. i.e. Looking at one particle on its own, I see it suddenly speeding up or slowing down, becuase another particle had hit a wall. This is because the display tick is not uniform. i.e. the frame rate update is changing, giving the false illusion that a particle is moving at non-constant speed while in fact it is moving at constant speed. The motion on the screen is not smooth, since the screen is not updating at constant rate. I am not able to figure how to fix this. If I want to show 2 particles at the moment of the collision, I must draw the screen at different times. Drawing the screen always at the same tick interval, results in seeing 2 particles before the collision, and then after the collision, and not just when they colliding, which looked bad when I tried it. So, how do real games handle this issue? How to display things in order to show collisions when it happen, yet keep the display tick constant? These 2 requirements seem to contradict each other’s.

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  • How to make a stack stable? Need help for an explicit resting contact scheme (2-dimensional)

    - by Register Sole
    Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based method with Projected-Gauss-Seidel (PGS) iterative solver as described by Erin Catto (mentioned in the reference of the paper as [Catt05]). So here's how it currently is: The simulation handles 2-dimensional rotating convex polygons. Detection is using separating-axis test, with a SKIN, meaning closest points between two polygons is detected and determined if their distance is less than SKIN. To resolve collision, simultaneous impulse-based method is used. It is solved using iterative solver (PGS-solver) as in Erin Catto's paper. Error-correction is implemented using Baumgarte's stabilization (you can refer to either paper for this) using J V = beta/dt*overlap, J is the Jacobian for the constraints, V the matrix containing the velocities of the bodies, beta an error-correction parameter that is better be < 1, dt the time-step taken by the engine, and overlap, the overlap between the bodies (true overlap, so SKIN is ignored). However, it is still less stable than I expected :s I tried to stack hexagons (or squares, doesn't really matter), and even with only 4 to 5 of them, they would swing! Also note that I am not looking for a sleeping scheme. But I would settle if you have any explicit scheme to handle resting contacts. That said, I would be more than happy if you have a way of treating it generally (as continuous collision, instead of explicitly as a special state). Ideas I have tried: Using simultaneous position based error correction as described in the paper in section 5.3.2, turned out to be worse than the current scheme. If you want to know the parameters I used: Hexagons, side 50 (pixels) gravity 2400 (pixels/sec^2) time-step 1/60 (sec) beta 0.1 restitution 0 to 0.2 coeff. of friction 0.2 PGS iteration 10 initial separation 10 (pixels) mass 1 (unit is irrelevant for now, i modified velocity directly<-impulse method) inertia 1/1000 Thanks in advance! I really appreciate any help from you guys!! :) EDIT In response to Cholesky's comment about warm starting the solver and Baumgarte: Oh right, I forgot to mention! I do save the contact history and the impulse determined in this time step to be used as initial guess in the next time step. As for the Baumgarte, here's what actually happens in the code. Collision is detected when the bodies' closest distance is less than SKIN, meaning they are actually still separated. If at this moment, I used the PGS solver without Baumgarte, restitution of 0 alone would be able to stop the bodies, separated by a distance of ~SKIN, in mid-air! So this isn't right, I want to have the bodies touching each other. So I turn on the Baumgarte, where its role is actually to pull the bodies together! Weird I know, a scheme intended to push the body apart becomes useful for the reverse. Also, I found that if I increase the number of iteration to 100, stacks become much more stable, though the program becomes so slow. UPDATE Since the stack swings left and right, could it be something is wrong with my friction model? Current friction constraint: relative_tangential_velocity = 0

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  • android listview button control

    - by Josemalive
    Hi, I have an android listview filled with items. Every item has a button. This is the template of the my listview. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:paddingBottom="6dip" android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal" android:paddingLeft="5px" android:paddingTop="5px" android:paddingRight="5px" android:gravity="left"> <TextView android:id="@+id/TextView_test1" android:layout_width="200dip" android:paddingLeft="0px" android:layout_height="wrap_content"/> <TextView android:id="@+id/TextView_test2" android:layout_width="250dip" android:paddingLeft="0px" android:layout_height="wrap_content" android:layout_weight="1"/> <TextView android:id="@+id/TextView_test3" android:layout_width="400dip" android:paddingLeft="0px" android:layout_height="wrap_content" android:layout_weight="1"/> <Button android:id="@+id/Button_buttontest" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/Button_buttontest"/> </LinearLayout> How could i handle the click of each button in the activity code? Each button has the same id "Button_buttontest"? Thanks in advance. Best Regards. Jose

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  • Android: failed to setContentView when switching to ListActivity

    - by Yang
    This is an follow-up issue on my previous question http://stackoverflow.com/questions/2548304/android-which-view-should-i-use-for-showing-text-and-image I read the article about creating ListView for LinearLayout. However, my following code failed at the setContentView() function when I changed "extends Activity" to "extends ListActivity", any idea why? private TextView mSelection; //private ImageView mImages; static final String[] keywords = new String[]{"China", "Japan", "USA", "Canada"}; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.contactLayout); mSelection = (TextView)findViewById(R.id.ContactNames); ArrayAdapter adapter = new ArrayAdapter<String>(this, R.layout.contactlayout, R.id.ContactNames,keywords); setListAdapter(adapter); } My Layout is from this article: http://www.curious-creature.org/2009/02/22/android-layout-tricks-1/ <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="?android:attr/listPreferredItemHeight" android:padding="6dip"> <ImageView android:id="@+id/icon" android:layout_width="wrap_content" android:layout_height="fill_parent" android:layout_marginRight="6dip" android:src="@drawable/icon" /> <LinearLayout android:orientation="vertical" android:layout_width="0dip" android:layout_weight="1" android:layout_height="fill_parent"> <TextView android:id="@+id/ContactNames" android:layout_width="fill_parent" android:layout_height="0dip" android:layout_weight="1" android:gravity="center_vertical" android:text="My Application" /> <TextView android:layout_width="fill_parent" android:layout_height="0dip" android:layout_weight="1" android:singleLine="true" android:ellipsize="marquee" android:text="Simple application that shows how to use RelativeLayout" /> </LinearLayout>

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  • How do I style buttons in a LinearLayout like a ListView

    - by Mannaz
    I have a vertically orientated LinearLayout with some Buttons in it: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical"> <Button android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/bt1" android:text="Button 1"></Button> <Button android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/bt2" android:text="Button 2"></Button> <Button android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/bt3" android:text="Button 3"></Button> <Button android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/bt4" android:text="Button 4"></Button> </LinearLayout> and I want this "List" of buttons to inherit the current style for ListView items. This is my current status of the stylesheet. The CKButton style gets applied over the Activity Theme. <style name="CKButton" parent="android:style/Widget.Button"> <item name="android:textSize">21sp</item> <item name="android:layout_margin">0dip</item> <!--<item name="android:background">@drawable/button_background</item>--> <item name="android:textColor">@color/button_text_normal</item> <item name="android:padding">10dip</item> <item name="android:gravity">left|center_horizontal</item> </style> As you see I tried to draw the button background myself, but depending on the system default theme the background-color changes and therefore defining a static color is not an option. Is there a way to inherit the default ListView Row background within that buttons?

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  • Contact-app like scrollinglist on android

    - by Alxandr
    I'm writing my first android app (I'm a noob at android, but decent at java). The first screen of the app consists of a huge list (about 1.5K items) of Manga-objects. The code I use is as following: main.xml: <?xml version="1.0" encoding="utf-8"?> <LinearLayout android:id="@+id/LinearLayout01" android:layout_width="fill_parent" android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android"> <ListView android:layout_height="fill_parent" android:layout_width="fill_parent" android:id="@+id/android:list"></ListView> <TextView android:layout_height="fill_parent" android:layout_width="fill_parent" android:text="@string/list_no_items" android:id="@+id/android:empty"></TextView> </LinearLayout> row.xml: <LinearLayout android:id="@+id/LinearLayout01" android:layout_width="fill_parent" android:layout_height="?android:attr/listPreferredItemHeight" android:padding="6dip" xmlns:android="http://schemas.android.com/apk/res/android"> <ImageView android:id="@+id/icon" android:layout_width="wrap_content" android:layout_height="fill_parent" android:layout_marginRight="6dip" android:src="@drawable/icon" /> <LinearLayout android:orientation="vertical" android:layout_width="0dip" android:layout_weight="1" android:layout_height="fill_parent"> <TextView android:id="@+id/toptext" android:layout_width="fill_parent" android:layout_height="0dip" android:layout_weight="1" android:gravity="center_vertical" /> <TextView android:layout_width="fill_parent" android:layout_height="0dip" android:layout_weight="1" android:id="@+id/bottomtext" android:singleLine="true" android:ellipsize="marquee" /> </LinearLayout> </LinearLayout> Then I have a adapter which basically takes a Manga-object and puts it's name in the rows toptext, and it's latest updated date in the bottomtext. However, (this might be caused by the virtualization of the unit though), the result is really slow. Scrolling the list takes forever and you can only scroll small peaces of the time. How can I make the list work like the one in the contacts-app? So that when you start scrolling a handle pops out at the right side of the screen, and when you drag it letters shows up as of how far you've scrolled (the list is sorted alphabetically), and also, is there a way I could improve the performance of the list?

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  • UIViewAnimationTransitionCurlUp in landscape mode transitioning right-to-left

    - by Thanos
    I have a view controller that is showing in portrait mode. When you touch the "menu" button, it calls the code below and it flips up to the MainMenu controller. So far, so good. - (void) menuButton: (id) sender { MainMenu_ViewController * viewController = [[MainMenu_ViewController alloc] initWithNibName:@"MainMenu_ViewController" bundle:nil]; self.menuView = viewController.view; self.menuView.frame = self.view.bounds; [viewController release]; [UIView beginAnimations:nil context: nil]; [UIView setAnimationDuration: 1.0]; [UIView setAnimationTransition: UIViewAnimationTransitionCurlUp forView: self.view cache: YES]; [self.view addSubview: self.menuView]; [UIView commitAnimations]; } However, when you do the same in landscape mode, instead of the animation flipping up (with respect to gravity, i.e. towards the long end of the iPhone) it flips towards the left (i.e. towards the short end of the iPhone). Is this a limitation of the animation, or am I missing something?

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  • Layout problem: how to place something on top and bottom?

    - by chow
    I want create a layout, with a horizontal LinearLayout(s) on top and bottom, a ListView fill in middle. How can I define the main.xml. I tried to create a layout with horizontal LinearLayout on top, TextView on bottom, a ListView fill in middle; is ok. But after I modified the bottom TextView to LinearLayout, the bottom LinearLayout disappear. <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="horizontal" > <TextView android:textSize="12px" android:text="something here" android:layout_width="50px" android:layout_height="wrap_content" /> <TextView android:textSize="12px" android:text="something here" android:layout_width="fill_parent" android:layout_height="wrap_content" /> </LinearLayout> <LinearLayout android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="bottom" > <ListView android:id="@+id/listbody" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <LinearLayout android:orientation="horizontal" android:layout_height="wrap_content" android:layout_width="fill_parent" > <TextView android:layout_height="wrap_content" android:layout_width="0dip" android:layout_weight="1" android:textSize="12px" android:text="50%" /> <TextView android:layout_height="wrap_content" android:layout_width="0dip" android:layout_weight="1" android:textSize="12px" android:text="50%" /> </LinearLayout> </LinearLayout> </LinearLayout> Anybody can tell advise? Please help.

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  • Problem with TextViews running into each other in RelativeLayout

    - by Janusz
    I have a problem with two Textviews on the same height in a RelativeLayout running into each other. I use the following Layout. <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent"> <ImageView android:id="@+id/logo" android:layout_width="wrap_content" android:layout_height="wrap_content" android:adjustViewBounds="true" android:scaleType="centerInside" android:src="@drawable/icon" /> <TextView android:id="@+id/name" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="NameNameNameNameNameNameName" android:layout_alignParentTop="true" android:layout_toRightOf="@id/logo" android:gravity="clip_horizontal" android:lines="1" /> <TextView android:id="@+id/information" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="information" android:layout_alignParentRight="true" android:layout_alignParentTop="true" /> <TextView android:id="@+id/nrcoupons" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Number" android:layout_alignRight="@id/information" android:layout_alignBottom="@id/logo" /> <TextView android:id="@+id/subcategory" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Subcategory" android:layout_alignLeft="@id/name" android:layout_alignBottom="@id/logo" /> </RelativeLayout> This gives me this view: Everything is as I need it except the two textviews name and information are displayed on the same screen space with the one on top of the other. How can I avoid this?

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  • Android - Views in Custom Compound Component are not inflated (findByView returns null)

    - by Julian Arz
    I have made a Custom Component in XML, consisting of a button with an imageview stacked on top of it: <myapp.widget.ClearableCaptionedButton xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="wrap_content" android:layout_height="wrap_content"> <Button android:id="@+id/ccbutton_button" android:layout_width="fill_parent" android:layout_height="wrap_content" android:gravity="center_vertical|left" android:textAppearance="?android:attr/textAppearanceMedium" android:background="@android:drawable/edit_text"/> <ImageView android:id="@+id/ccbutton_clear" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginRight="5dip" android:layout_alignRight="@id/ccbutton_button" android:layout_alignTop="@id/ccbutton_button" android:layout_alignBottom="@id/ccbutton_button"/> </myapp.widget.ClearableCaptionedButton> extract of java source code: public class ClearableCaptionedButton extends RelativeLayout implements OnClickListener { ... public ClearableCaptionedButton(Context context, AttributeSet attrs) { super(context, attrs); // some stuff that works fine } .. protected void onFinishInflate() { super.onFinishInflate(); mButton = (Button) findViewById(R.id.ccbutton_button); mClear = (ImageView) findViewById(R.id.ccbutton_clear); mButton.setText(""); // error here: mButton == null } My problem is similar to this one. When i try to find the views inside the custom compound, findViewById returns null. But, as you can see, i already added super(context, attrs); to the constructor. i am using the custom component directly in xml layout, like this: <LinearLayout> <!-- some stuff --> <de.pockettaxi.widget.ClearableCaptionedButton android:layout_width="fill_parent" android:layout_height="wrap_content" app:caption="to"/> </LinearLayout> can anybody spot something? thanks.

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  • imageview weights in linearlayout

    - by Metalex
    I have this layout: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center_vertical" android:orientation="horizontal" android:minWidth="100dp" > <TextView android:id="@+id/txt_what_way" android:layout_height="wrap_content" android:layout_width="0dp" android:layout_weight="4" android:textAppearance="?android:attr/textAppearanceMedium" /> <LinearLayout android:layout_height="wrap_content" android:layout_width="0dp" android:layout_weight="3"> <ImageView android:layout_width="20dp" android:layout_height="20dp" android:scaleType="fitCenter" android:src="@drawable/ic_launcher"/> </LinearLayout> <LinearLayout android:layout_height="wrap_content" android:layout_width="0dp" android:layout_weight="3"> <ImageView android:layout_width="20dp" android:layout_height="20dp" android:scaleType="fitCenter" android:src="@drawable/ic_launcher"/> </LinearLayout> </LinearLayout> I want that it looks like: TextView - 40% of width, Layout with ImageView - 30% of widht, Layout with ImageView - 30% of width. But the output is: TextViewImageViewImageView----------------free space---------------------------------- Thanks for your help! -- EDITED Done it in programmatic way

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  • Android application transparency and window sizing at root level

    - by ajoburg
    Is it possible to create an application with a transparent background on the root task such that you can see the task running beneath it when it is part of a separate stack? Alternatively, is it possible to run an application so the window of the root task is only a portion of the screen instead of the whole screen? I understand how the transparency and window sizing is done with activities that are not the root task and this works fine. However, the root task of an activity seems to always fill the whole screen and be black even when a transparent theme is applied to the application object in the manifest file. ApplicationManifest.xml: <application android:icon="@drawable/icon" android:label="@string/app_name" android:debuggable="true" android:theme="@style/Theme.Transparent"> Styles.xml <resources> <style name="Theme.Transparent"> <item name="android:windowIsTranslucent">true</item> <item name="android:windowNoTitle">true</item> <item name="android:windowBackground">@drawable/ transparent_background</item> <item name="android:windowAnimationStyle">@android:style/ Animation.Translucent</item> <item name="android:colorForeground">#fff</item> <item name="android:windowIsFloating">true</item> <item name="android:gravity">bottom</item> </style> </resources> Colors.xml <resources> <drawable name="transparent_background">#00000000</drawable> </resources>

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  • Changing text of TextView -- old text doesn't go away (Android 4.1.2)

    - by Jason Costabile
    I'm pretty new to Android development. Trying to accomplish something fairly simple -- change some displayed text when a timer ticks. Here's the potentially relevant code: CountDownTimer currentTimer; Resources res; TextView timerText; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_exercise); res = getResources(); timerText = (TextView) findViewById(R.id.timer_text); } @Override protected void onStart() { super.onStart(); //"Get ready" countdown currentTimer = new CountDownTimer(5000, 1000) { @Override public void onTick(long millisUntilFinished) { timerText.setText("" + (int)Math.ceil(millisUntilFinished / 1000.0)); } @Override public void onFinish() { ... } }; currentTimer.start(); } This works fine on an emulated 4.2.2 device, but on a 4.1.2 device (both physical and emulated), the changed TextView appears as such while the countdown proceeds: If you can't tell, that's the numbers 5,4,3 overlayed. So, when I set a new string for the TextView, the new string is displayed but without replacing the old string. Any other TextViews used in my app behave in the same way. Any ideas what the problem is and how to fix it? Edit: From the XML layout file: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" tools:context=".ExerciseActivity" android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center" android:keepScreenOn="true" android:orientation="vertical" > ... <TextView android:id="@+id/timer_text" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" android:textIsSelectable="false" android:hint="@string/timer_default" /> ... </LinearLayout> That's all that could be relevant.

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