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• GWT: What is the way to handle Click on GWT FlowPanel

  - by shaman.sir

  May be a dumb question, but GWT FlowPanel (raw div element) does not provides something to handle a mouseclick/mousemovement on it. Overriding onBrowserEvent do not works either. If setting onclick event using native JavaScript (need to specify positive height before, 'div' have a height of 0 if not specified), then catching these events is working properly. Is there a way to do it without using JSNI?

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• Pointing layout_above to an external ID?

  - by Joren

  When I try to use layout_above to position a view above another view, it can't find the ID if it's not in the same XML file. I'm adding my XML files at run time but I still want to be able to position them relative to eachother. Any suggestions?

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• Return type value if RunTimeException has been thrown and not catched.

  - by Alfred

  I am using Gson to parse Json. What I don't understand what the return type will be if you don't catch the Runtime Exception. I was expecting it to be null, but it is not null when evaluating with a simple if statement. My code looks something like this: public X x() { return gson.fromJson(jsonString, X.class); } then from another function I call the function: public void y() { final X x = x(); if (x == null) { System.out.println("x == null") } } I was expecting x to be null, but it isn't because the print statement is not called? What is the value of x? How can if them. I have my problem by using a catch block in the x() function and returning null. But I am just wondering what the value of function x() is(if any?)? Hopefully I make any sense at all.

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• How to reference an embedded JCA resource adapater

  - by cg

  For our current J2EE project based on JBoss, we need to interface with a remote system using message driven beans and a JCA resource adapter provided as a RAR file by a third party. I would like to package and deploy the entire project as an EAR file to our JBoss server. Most notably, the RAR file should be embedded within the EAR file and not be deployed globally. All of this is working fine so far, but I'm not particularly happy with the way the RAR file is referenced. The jboss.xml packaged with the MDB for example, currently looks like this: <jboss> <enterprise-beans> <message-driven> <ejb-name>testBean1</ejb-name> <resource-adapter-name>test1.ear#thirdparty-1.0.rar</resource-adapter-name> </message-driven> </enterprise-beans> </jboss> While this is generally working fine, it will break when the EAR file is renamed to "test2.ear". Is there a way to reference the embedded RAR file without hard-coding the containing archive's name?

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• How can I create an animation frame with netbeans?

  - by Johanna

  I use netbeans,and I insert an image on the lable which is on the desktop pane ,I want to rotate that image in its place ,what should i do? please help me. thanks.

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• Duplicate Prefix Error in Jsp page with Struts

  - by Cricandcric.com

  Hi, i am creating and Configuring the Struts for the first time, when I place the following Code in my jsp page <%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%> <%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%> <%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic"%> <%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles"%> I am getting the error when i move the mouse over the 1st Line "Duplicate Prefix "html" When I move the mouse over the 2nd Line, I am getting as "Duplicate Prefix "html" Similarly for 3rd and 4th Line, Can any one tell me why is this error all about Thanks in advance

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• How does Hibernate detect dirty state of an entity object?

  - by ???'Lenik

  Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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• How to copy generically superclass instances to subclass instances?

  - by gerry

  Hi @all, I have a class hierarchy / inheritance like this: public class A { private String name; // with getters & setters public void doAWithName(){ ... } } public class B extends A { public void doBWithName(){ // a differnt implementation to what I do in class A } } public class C extends B { public void doCWithName(){ // a differnt implementation to what I do in class A and B } } So at one time there is a instance of class A with the initialized field "name". Later I want this instance of A get wrapped into instance of B or C. So the superclasses should be get wrapped with a subclass! How can I make this most efficent with respect to DRY? I've thought about a constructor that does some copying with the getters/setters. But in this case I have to repeat myself - and this doesn't respect anymore to my initial requirement of DRY! So, how can I warp A to B by just initializing B's new fields (with default values) and delegating the rest to a method in A (which knows more than B about which fields of A should be accessed...). In the same way: If A should be wrapped into C only a method in c should init C's 'new' fields, delegate to B's wrap method (which therefore inits B's 'new' fields in C) and at last B delegates to A which copies it's fields to the fields of C). So in the end I have a new instance of C which has the values of A wrapped (and some default init values to the fields which the inheritance hierarchy has added).

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• Handling multiple exceptions

  - by the-banana-king

  Hi there, I have written a class which loads configuration objects of my application and keeps track of them so that I can easily write out changes or reload the whole configuration at once with a single method call. However, each configuration object might potentially throw an exception when doing IO, yet I do not want those errors to cancel the overall process so that the other objects are still given a chance to reload/write. Therefore I collect all exceptions which are thrown while iterating over the objects and store them in a super-exception, which is thrown after the loop, since each exception must still be handled and someone has to be notified of what exactly went wrong. However, that approach looks a bit odd to me. Someone out there with a cleaner solution? Here is some code of the mentioned class: public synchronized void store() throws MultipleCauseException { MultipleCauseException me = new MultipleCauseException("unable to store some resources"); for(Resource resource : this.resources.values()) { try { resource.store(); } catch(StoreException e) { me.addCause(e); } } if(me.hasCauses()) throw me; }

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• Displaying NON-ASCII Characters using HttpClient

  - by Abdullah Gheith

  So, i am using this code to get the whole HTML of a website. But i dont seem to get non-ascii characters with me. all i get is diamonds with question mark. characters like this: å, appears like this: ? I doubt its because of the charset, what could it then be? Log.e("HTML", "henter htmlen.."); String url = "http://beep.tv2.dk"; HttpClient client = new DefaultHttpClient(); client.getParams().setParameter(CoreProtocolPNames.PROTOCOL_VERSION, HttpVersion.HTTP_1_1); client.getParams().setParameter(CoreProtocolPNames.HTTP_ELEMENT_CHARSET, "UTF-8"); HttpGet request = new HttpGet(url); HttpResponse response = client.execute(request); Header h = HeaderValueFormatter response.addHeader(header) String html = ""; InputStream in = response.getEntity().getContent(); BufferedReader reader = new BufferedReader(new InputStreamReader(in)); StringBuilder str = new StringBuilder(); String line = null; while((line = reader.readLine()) != null) { str.append(line); } in.close(); //b = false; html = str.toString();

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• log4j relative file path

  - by Bob

  Hi, I'd like my web app to log into files with this path: webapp/logs/ I can set the absolute path in the log4j.properties file, but the production environment's directory structure will be different. Is there any way I could do it? Here is how I do: log4j.appender.f=org.apache.log4j.RollingFileAppender log4j.appender.f.layout=org.apache.log4j.PatternLayout log4j.appender.f.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n log4j.appender.f.File=log.out log4j.appender.f.MaxFileSize=100KB This is printing logs into a file named log.log in my eclipse directory (c://eclipse). I'm using Tomcat 6.

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• When to use LinkedList<> over ArrayList<>?

  - by sdellysse

  I've always been one to simply use List<String> names = new ArrayList<String>(); I use the interface as the type name for portability, so that when I ask questions such as these I can rework my code. When should LinkedList should be used over ArrayList and vice-versa?

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• How significant are JPA lazy loading performance benefits?

  - by Robert

  I understand that this is highly specific to the concrete application, but I'm just wondering what's the general opinion, or at least some personal experiences on the issue. I have an aversion towards the 'open session in view' pattern, so to avoid it, I'm thinking about simply fetching everything small eagerly, and using queries in the service layer to fetch larger stuff. Has anyone used this and regretted it? And is there maybe some elegant solution to lazy loading in the view layer that I'm not aware of?

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• Intermittent Issue Writing to Google Appengine Datastore

  - by user242153

  Hi, I have a functioning app and recently have had intermittent problems writing to the datastore. I did not make any relevant code changes, however in the last few days my attempts to write to the datastore sometimes work and sometimes don't. I am trying to save an object that is in a many to one relationship with an existing persisted parent. So, the logic works like this: 1) Parent pulled from the datastore 2) Child created / instantiated using constructor 3) Parent.addSingleChild(child); // the "addSingleChild" method just adds the object argument to the collection of children 4) child.setParent(Parent); // sets the Parent object to the parent field I am using transactions as explained in the documentation ending with "finally {if (tx.isActive()) {tx.rollback(); } }" When the servlet is called, the parent is called from the datastore and the child object is created and added to the many to one mapping to the pre-existing parent. The child should automatically be persisted, since the parent is already persistent, and the child is added to the collection of children that map to the parent. And it worked this way in the past. However, to be sure, i did add a pm.makePersistent(child). Doesn't seem to help, still have the intermittent problem. Any suggestions would be appreciated, and if you need to see the actual code I can post. Thanks

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• Recover from an OutOfMemoryError without a restart

  - by askullhead

  Can the JVM recover from an OutOfMemoryError without a restart if it gets a chance to run the GC before more object allocation requests come in? Do the various JVM implementations differ in this aspect?

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• JAX-WS vs Restlet Framework for Web Services

  - by artgon

  Which is the better options? Pros and cons of each? The web services are meant to be internal-facing and are all going to be roughly in the same datacenter (3-4km apart at most). Any ideas?

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• What could be the reason for continuous Full GC's during application startup.

  - by Kumar225

  What could be the reason for continuous Full GC's during application (webapplication deployed on tomcat) startup? JDK 1.6 Memory settings -Xms1024M -Xmx1024M -XX:PermSize=200M -XX:MaxPermSize=512M -XX:+UseParallelOldGC jmap output is below Heap Configuration: MinHeapFreeRatio = 40 MaxHeapFreeRatio = 70 MaxHeapSize = 1073741824 (1024.0MB) NewSize = 2686976 (2.5625MB) MaxNewSize = 17592186044415 MB OldSize = 5439488 (5.1875MB) NewRatio = 2 SurvivorRatio = 8 PermSize = 209715200 (200.0MB) MaxPermSize = 536870912 (512.0MB) 0.194: [GC [PSYoungGen: 10489K->720K(305856K)] 10489K->720K(1004928K), 0.0061190 secs] [Times: user=0.01 sys=0.00, real=0.00 secs] 0.200: [Full GC (System) [PSYoungGen: 720K->0K(305856K)] [ParOldGen: 0K->594K(699072K)] 720K->594K(1004928K) [PSPermGen: 6645K->6641K(204800K)], 0.0516540 secs] [Times: user=0.10 sys=0.00, real=0.06 secs] 6.184: [GC [PSYoungGen: 262208K->14797K(305856K)] 262802K->15392K(1004928K), 0.0354510 secs] [Times: user=0.18 sys=0.04, real=0.03 secs] 9.549: [GC [PSYoungGen: 277005K->43625K(305856K)] 277600K->60736K(1004928K), 0.0781960 secs] [Times: user=0.56 sys=0.07, real=0.08 secs] 11.768: [GC [PSYoungGen: 305833K->43645K(305856K)] 322944K->67436K(1004928K), 0.0584750 secs] [Times: user=0.40 sys=0.05, real=0.06 secs] 15.037: [GC [PSYoungGen: 305853K->43619K(305856K)] 329644K->72932K(1004928K), 0.0688340 secs] [Times: user=0.42 sys=0.01, real=0.07 secs] 19.372: [GC [PSYoungGen: 273171K->43621K(305856K)] 302483K->76957K(1004928K), 0.0573890 secs] [Times: user=0.41 sys=0.01, real=0.06 secs] 19.430: [Full GC (System) [PSYoungGen: 43621K->0K(305856K)] [ParOldGen: 33336K->54668K(699072K)] 76957K->54668K(1004928K) [PSPermGen: 36356K->36296K(204800K)], 0.4569500 secs] [Times: user=1.77 sys=0.02, real=0.46 secs] 19.924: [GC [PSYoungGen: 4280K->128K(305856K)] 58949K->54796K(1004928K), 0.0041070 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 19.928: [Full GC (System) [PSYoungGen: 128K->0K(305856K)] [ParOldGen: 54668K->54532K(699072K)] 54796K->54532K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.3531480 secs] [Times: user=1.19 sys=0.10, real=0.35 secs] 20.284: [GC [PSYoungGen: 4280K->64K(305856K)] 58813K->54596K(1004928K), 0.0040580 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 20.288: [Full GC (System) [PSYoungGen: 64K->0K(305856K)] [ParOldGen: 54532K->54532K(699072K)] 54596K->54532K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2360580 secs] [Times: user=1.01 sys=0.01, real=0.24 secs] 20.525: [GC [PSYoungGen: 4280K->96K(305856K)] 58813K->54628K(1004928K), 0.0030960 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 20.528: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54532K->54533K(699072K)] 54628K->54533K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2311320 secs] [Times: user=0.88 sys=0.00, real=0.23 secs] 20.760: [GC [PSYoungGen: 4280K->96K(305856K)] 58814K->54629K(1004928K), 0.0034940 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 20.764: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54533K->54533K(699072K)] 54629K->54533K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2381600 secs] [Times: user=0.85 sys=0.01, real=0.24 secs] 21.201: [GC [PSYoungGen: 5160K->354K(305856K)] 59694K->54888K(1004928K), 0.0019950 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 21.204: [Full GC (System) [PSYoungGen: 354K->0K(305856K)] [ParOldGen: 54533K->54792K(699072K)] 54888K->54792K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2358570 secs] [Times: user=0.98 sys=0.01, real=0.24 secs] 21.442: [GC [PSYoungGen: 4280K->64K(305856K)] 59073K->54856K(1004928K), 0.0022190 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 21.444: [Full GC (System) [PSYoungGen: 64K->0K(305856K)] [ParOldGen: 54792K->54792K(699072K)] 54856K->54792K(1004928K) [PSPermGen: 36300K->36300K(204800K)], 0.2475970 secs] [Times: user=0.95 sys=0.00, real=0.24 secs] 21.773: [GC [PSYoungGen: 11200K->741K(305856K)] 65993K->55534K(1004928K), 0.0030230 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 21.776: [Full GC (System) [PSYoungGen: 741K->0K(305856K)] [ParOldGen: 54792K->54376K(699072K)] 55534K->54376K(1004928K) [PSPermGen: 36538K->36537K(204800K)], 0.2550630 secs] [Times: user=1.05 sys=0.00, real=0.25 secs] 22.033: [GC [PSYoungGen: 4280K->96K(305856K)] 58657K->54472K(1004928K), 0.0032130 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] 22.036: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54376K->54376K(699072K)] 54472K->54376K(1004928K) [PSPermGen: 36537K->36537K(204800K)], 0.2507170 secs] [Times: user=1.01 sys=0.01, real=0.25 secs] 22.289: [GC [PSYoungGen: 4280K->96K(305856K)] 58657K->54472K(1004928K), 0.0038060 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 22.293: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54376K->54376K(699072K)] 54472K->54376K(1004928K) [PSPermGen: 36537K->36537K(204800K)], 0.2640250 secs] [Times: user=1.07 sys=0.02, real=0.27 secs] 22.560: [GC [PSYoungGen: 4280K->128K(305856K)] 58657K->54504K(1004928K), 0.0036890 secs] [Times: user=0.01 sys=0.00, real=0.01 secs] 22.564: [Full GC (System) [PSYoungGen: 128K->0K(305856K)] [ParOldGen: 54376K->54377K(699072K)] 54504K->54377K(1004928K) [PSPermGen: 36537K->36536K(204800K)], 0.2585560 secs] [Times: user=1.08 sys=0.01, real=0.25 secs] 22.823: [GC [PSYoungGen: 4533K->96K(305856K)] 58910K->54473K(1004928K), 0.0020840 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] 22.825: [Full GC (System) [PSYoungGen: 96K->0K(305856K)] [ParOldGen: 54377K->54377K(699072K)] 54473K->54377K(1004928K) [PSPermGen: 36536K->36536K(204800K)], 0.2505380 secs] [Times: user=0.99 sys=0.01, real=0.25 secs] 23.077: [GC [PSYoungGen: 4530K->32K(305856K)] 58908K->54409K(1004928K), 0.0016220 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 23.079: [Full GC (System) [PSYoungGen: 32K->0K(305856K)] [ParOldGen: 54377K->54378K(699072K)] 54409K->54378K(1004928K) [PSPermGen: 36536K->36536K(204800K)], 0.2320970 secs] [Times: user=0.95 sys=0.00, real=0.23 secs] 24.424: [GC [PSYoungGen: 87133K->800K(305856K)] 141512K->55179K(1004928K), 0.0038230 secs] [Times: user=0.01 sys=0.01, real=0.01 secs] 24.428: [Full GC (System) [PSYoungGen: 800K->0K(305856K)] [ParOldGen: 54378K->54950K(699072K)] 55179K->54950K(1004928K) [PSPermGen: 37714K->37712K(204800K)], 0.4105190 secs] [Times: user=1.25 sys=0.17, real=0.41 secs] 24.866: [GC [PSYoungGen: 4280K->256K(305856K)] 59231K->55206K(1004928K), 0.0041370 secs] [Times: user=0.01 sys=0.00, real=0.00 secs] 24.870: [Full GC (System) [PSYoungGen: 256K->0K(305856K)] [ParOldGen: 54950K->54789K(699072K)] 55206K->54789K(1004928K) [PSPermGen: 37720K->37719K(204800K)], 0.4160520 secs] [Times: user=1.12 sys=0.19, real=0.42 secs] 29.041: [GC [PSYoungGen: 262208K->12901K(275136K)] 316997K->67691K(974208K), 0.0170890 secs] [Times: user=0.11 sys=0.00, real=0.02 secs]

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• Rounding up milliseconds when printing with Joda Time

  - by RoToRa

  I'm implementing a count-down using Joda Time. I only need a display accuracy of seconds. However when printing the time, the seconds are displayed as full seconds, so when the count down reaches, for example, 900ms, then "0" seconds is printed, but as a count-down it would make more sense to display "1" second, until the time actually reaches 0ms. Example: void printDuration(Duration d) { System.out.println( d.toPeriod(PeriodType.time()).toString( new PeriodFormatterBuilder().printZeroAlways().appendSeconds().toFormatter() ) ); } printDuration(new Duration(5000)); // Prints "5" => OK printDuration(new Duration(4900)); // Prints "4" => need "5" printDuration(new Duration(1000)); // Prints "1" => OK printDuration(new Duration(900)); // Prints "0" => need "1" printDuration(new Duration(0)); // Prints "0" => OK Basically I need to the seconds to be display rounded up from milliseconds and not rounded down. Is there a way to achieve this with Joda without needing to write my own formatter?

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• Generate Javadoc for interfaces only using Ant script?

  - by ipkiss

  Hi all, I am using Apache Ant to generate Javadoc for my program which has many projects(or modules). However, I just want to generate Javadoc for Interfaces ONLY and I do not know how to check if a file is a class or interface in Ant. Someone suggested me that I should use and specify a list of files to exclude or include. However, there are hundreds of files in my program and specifying a list of class files to exclude is impossible. Does anyone have some ideas, please?

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• garbage collector Issue

  - by Eslam

  this question is like my previous one Given: 3. interface Animal { void makeNoise(); } 4. class Horse implements Animal { 5. Long weight = 1200L; 6. public void makeNoise() { System.out.println("whinny"); } 7. } 8. public class Icelandic extends Horse { 9. public void makeNoise() { System.out.println("vinny"); } 10. public static void main(String[] args) { 11. Icelandic i1 = new Icelandic(); 12. Icelandic i2 = new Icelandic(); 13. Icelandic i3 = new Icelandic(); 14. i3 = i1; i1 = i2; i2 = null; i3 = i1; 15. } 16. } When line 14 is reached, how many objects are eligible for the garbage collector? A. 0 B. 1 C. 2 D. 3 E. 4 F. 6 i choosed A but the right answer is E, but i don't know Why?

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• Hibernate configuration - session factory scanning?

  - by Marcus

  We have this hibernate.cfg.xml file. Is there a way to tell Hibernate to just scan a directory instead of having to add an entry here for each class? <hibernate-configuration> <session-factory> <mapping class="com.abc.domain.model.A" /> <mapping class="com.abc.domain.model.B" /> <mapping class="com.abc.domain.model.C" /> <mapping class="com.abc.domain.model.D" /> <mapping class="com.abc.domain.model.E" /> </session-factory> </hibernate-configuration>

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• Going "behind Hibernate's back" to update foreign key values without an associated entity

  - by Alex Cruise

  Updated: I wound up "solving" the problem by doing the opposite! I now have the entity reference field set as read-only (insertable=false updatable=false), and the foreign key field read-write. This means I need to take special care when saving new entities, but on querying, the entity properties get resolved for me. I have a bidirectional one-to-many association in my domain model, where I'm using JPA annotations and Hibernate as the persistence provider. It's pretty much your bog-standard parent/child configuration, with one difference being that I want to expose the parent's foreign key as a separate property of the child alongside the reference to a parent instance, like so: @Entity public class Child { @Id @GeneratedValue Long id; @Column(name="parent_id", insertable=false, updatable=false) private Long parentId; @ManyToOne(cascade=CascadeType.ALL) @JoinColumn(name="parent_id") private Parent parent; private long timestamp; } @Entity public class Parent { @Id @GeneratedValue Long id; @OrderBy("timestamp") @OneToMany(mappedBy="parent", cascade=CascadeType.ALL, fetch=FetchType.LAZY) private List<Child> children; } This works just fine most of the time, but there are many (legacy) cases when I'd like to put an invalid value in the parent_id column without having to create a bogus Parent first. Unfortunately, Hibernate won't save values assigned to the parentId field due to insertable=false, updatable=false, which it requires when the same column is mapped to multiple properties. Is there any nice way to "go behind Hibernate's back" and sneak values into that field without having to drop down to JDBC or implement an interceptor? Thanks!

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• Hibernate session method to update object

  - by EugeneP

  I need this roadmap of a Hibernate managed object instance. First, I create an instance with initial properties and persist this object in a db. Then session associated with this object is closed. But still, I serialize my object and on the next step deserialize it, invoke some setters, and again, I need to update what changed in a database. What methods of Hibernate session should I use? persist() or save() on the first step and saveOrUpdate() on the second? In fact I see that saveOrUpdate() can be used on each step. What would you recommend?

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• Thread used for ServiceConnection callback (Android)

  - by Jannick

  Hi I'm developing an activity that binds to a local service (in onCreate of the activity): bindService(new Intent(this, CommandService.class), svcConn, BIND_AUTO_CREATE); I would like to be able to call methods through the IBinder in my lifecycle methods, but can not be sure that onServiceConnected have been called prior to these. I'm thinking of handling this by adding a queue of sorts in the ServiceConnection implementation, so that the method calls (Command pattern) will be executed once the connection is established. My questions are then: Is this stupid, any better ways? :) Are there any specification for which thread will be used to execute the ServiceConnection callbacks? More to the point, do I need to worry about synchronizing a queue datastructure? Edit - something like: public void onServiceConnected(ComponentName name, IBinder service) { dispatchService = (DispatchAsync)service; for(ExecutionTask task : queue){ dispatchService.execute(task.getCommand(), task); } }

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• Collision problems with drag-n-drop puzzle game.

  - by Amplify91

  I am working on an Android game similar to the Rush Hour/Traffic Jam/Blocked puzzle games. The board is a square containing rectangular pieces. Long pieces may only move horizontally, and tall pieces may only move vertically. The object is to free the red piece and move it out of the board. This game is only my second ever programming project in any language, so any tips or best practices would be appreciated along with your answer. I have a class for the game pieces called Pieces that describes how they are sized and drawn to the screen, gives them drag-and-drop functionality, and detects and handles collisions. I then have an activity class called GameView which creates my layout and creates Pieces objects to add to a RelativeLayout called Board. I have considered making Board its own class, but haven't needed to yet. Here's what my work in progress looks like: My Question: Most of this works perfectly fine except for my collision handling. It seems to be detecting collisions well but instead of pushing the pieces outside of each other when there is a collision, it frantically snaps back and forth between (what seems to be) where the piece is being dragged to and where it should be. It looks something like this: Another oddity: when the dragged piece collides with a piece to its left, the collision handling seems to work perfectly. Only piece above, below, and to the right cause problems. Here's the collision code: @Override public boolean onTouchEvent(MotionEvent event){ float eventX = event.getX(); float eventY = event.getY(); switch (event.getAction()) { case MotionEvent.ACTION_DOWN: //check if touch is on piece if (eventX > x && eventX < (x+width) && eventY > y && eventY < (y+height)){ initialX=x; initialY=y; break; }else{ return false; } case MotionEvent.ACTION_MOVE: //determine if piece should move horizontally or vertically if(width>height){ for (Pieces piece : aPieces) { //if object equals itself in array, skip to next object if(piece==this){ continue; } //if next to another piece, //do not allow to move any further towards said piece if(eventX<x&&(x==piece.right+1)){ return false; }else if(eventX>x&&(x==piece.x-width-1)){ return false; } //move normally if no collision //if collision, do not allow to move through other piece if(collides(this,piece)==false){ x = (eventX-(width/2)); }else if(collidesLeft(this,piece)){ x = piece.right+1; break; }else if(collidesRight(this,piece)){ x = piece.x-width-1; break; } } break; }else if(height>width){ for (Pieces piece : aPieces) { if(piece==this){ continue; }else if(collides(this,piece)==false){ y = (eventY-(height/2)); }else if(collidesUp(this,piece)){ y = piece.bottom+1; break; }else if(collidesDown(this,piece)){ y = piece.y-height-1; break; } } } invalidate(); break; case MotionEvent.ACTION_UP: // end move if(this.moves()){ GameView.counter++; } initialX=x; initialY=y; break; } // parse puzzle invalidate(); return true; } This takes place during onDraw: width = sizedBitmap.getWidth(); height = sizedBitmap.getHeight(); right = x+width; bottom = y+height; My collision-test methods look like this with different math for each: private boolean collidesDown(Pieces piece1, Pieces piece2){ float x1 = piece1.x; float y1 = piece1.y; float r1 = piece1.right; float b1 = piece1.bottom; float x2 = piece2.x; float y2 = piece2.y; float r2 = piece2.right; float b2 = piece2.bottom; if((y1<y2)&&(y1<b2)&&(b1>=y2)&&(b1<b2)&&((x1>=x2&&x1<=r2)||(r1>=x2&&x1<=r2))){ return true; }else{ return false; } } private boolean collides(Pieces piece1, Pieces piece2){ if(collidesLeft(piece1,piece2)){ return true; }else if(collidesRight(piece1,piece2)){ return true; }else if(collidesUp(piece1,piece2)){ return true; }else if(collidesDown(piece1,piece2)){ return true; }else{ return false; } } As a second question, should my x,y,right,bottom,width,height variables be ints instead of floats like they are now? Also, any suggestions on how to implement things better would be greatly appreciated, even if not relevant to the question! Thanks in advance for the help and for sitting through such a long question! Update: I have gotten it working almost perfectly with the following code (this doesn't include the code for vertical pieces): @Override public boolean onTouchEvent(MotionEvent event){ float eventX = event.getX(); float eventY = event.getY(); switch (event.getAction()) { case MotionEvent.ACTION_DOWN: //check if touch is on piece if (eventX > x && eventX < (x+width) && eventY > y && eventY < (y+height)){ initialX=x; initialY=y; break; }else{ return false; } case MotionEvent.ACTION_MOVE: //determine if piece should move horizontally or vertically if(width>height){ for (Pieces piece : aPieces) { //if object equals itself in array, skip to next object if(piece==this){ continue; } //check if there the possibility for a horizontal collision if(this.isAllignedHorizontallyWith(piece)){ //check for and handle collisions while moving left if(this.isRightOf(piece)){ if(eventX>piece.right+(width/2)){ x = (int)(eventX-(width/2)); //move normally }else{ x = piece.right+1; } } //check for and handle collisions while moving right if(this.isLeftOf(piece)){ if(eventX<piece.x-(width/2)){ x = (int)(eventX-(width/2)); }else{ x = piece.x-width-1; } } break; }else{ x = (int)(eventX-(width/2)); } The only problem with this code is that it only detects collisions between the moving piece and one other (with preference to one on the left). If there is a piece to collide with on the left and another on the right, it will only detect collisions with the one on the left. I think this is because once it finds a possible collision, it handles it without finishing looping through the array holding all the pieces. How do I get it to check for multiple possible collisions at the same time?

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