My App consists of 2 Activities at the moment. . the MAIN activity with a Gallery View . a FriendsListActivity with a ListView

When the user moves away from the FriendsListActivity with the back button, and returns to the MAIN activity the following error keeps popping up in debug mode.

DalvikVM[localhost:8676] Thread [<1> main] (Suspended (exception RuntimeException))
ActivityThread.performResumeActivity(IBinder, boolean) line: 2095
ActivityThread.handleResumeActivity(IBinder, boolean, boolean) line: 2110
BinderProxy(ActivityThread$H).handleMessage(Message) line: 954 ActivityThread$H(Handler).dispatchMessage(Message) line: 99 Looper.loop() line: 123 ActivityThread.main(String[]) line: 3647 Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method] Method.invoke(Object, Object...) line: 507
ZygoteInit$MethodAndArgsCaller.run() line: 839 ZygoteInit.main(String[]) line: 597 NativeStart.main(String[]) line: not available [native method] Thread [<8> Binder Thread #2] (Running)
Thread [<7> Binder Thread #1] (Running)

With the LogCat

03-13 22:01:10.972: ERROR/AndroidRuntime(1038): FATAL EXCEPTION: main 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): java.lang.RuntimeException: Unable to resume activity {com.package.MAIN/com.package.MAIN.MAIN}: java.lang.NullPointerException 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2095) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2110) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:954) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.os.Handler.dispatchMessage(Handler.java:99) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.os.Looper.loop(Looper.java:123) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread.main(ActivityThread.java:3647) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at java.lang.reflect.Method.invokeNative(Native Method) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at java.lang.reflect.Method.invoke(Method.java:507) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at dalvik.system.NativeStart.main(Native Method) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): Caused by: java.lang.NullPointerException 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at com.package.MAIN.MAIN.onResume(MAIN.java:91) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1149) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.Activity.performResume(Activity.java:3833) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2085) 03-13 22:01:10.972: ERROR/AndroidRuntime(1038): ... 10 more

Further info in the Variables panel states:
this: ActivityThread
e: NullPointerException
cause: NullPointerException
detailMessage: null
stackTrace: null
r: ActivityThread$ActivityClientRecord
activity: MAIN

detailMessage after one Eclipse Resume: Unable to resume activity (MAIN)

The code from the FriendsListActivity looks like this

public class FriendsListActivity extends ListActivity {

// ===========================================================
// Fields
// ===========================================================

private ArrayList<Friend> friends = new ArrayList<Friend>();
private FriendsArrayAdapter friendsArrayAdapter;
private ListView listView;

// ===========================================================
// onCreate
// ===========================================================

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.friends_list);

    registerForContextMenu(getListView());
    setButtonNewFriendClickListener();
}

public void generateFriendsList() {
    FriendsService fs = new FriendsService(this);
    friends = fs.getFriendsList();

    listView = (ListView) findViewById(android.R.id.list);
    friendsArrayAdapter = new FriendsArrayAdapter(
       this, R.layout.friend_list_item, friends);
    listView.setAdapter(friendsArrayAdapter);
}

@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
    super.onCreateContextMenu(menu, v, menuInfo);
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.friends_context_menu, menu);
}

@Override
public boolean onContextItemSelected(MenuItem item) {
    AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
    FriendsService fs = new FriendsService(this);
    Friend f = new Friend();
    f = friends.get(info.position);
    switch (item.getItemId()) {
    case R.id.edit:
        Intent i = new Intent(this, FriendEditActivity.class);
        i.putExtra("userid", f.userId);
        startActivity(i);
        return true;
    case R.id.delete:
        fs.deleteFriend(f.userId);
        generateFriendsList();
        return true;
    default:
        return super.onContextItemSelected(item);
    }
}

// ===========================================================
// onPause
// ===========================================================

protected void onPause() {
    super.onPause();
    finish();
}

// ===========================================================
// onResume
// ===========================================================

protected void onResume() {
    super.onResume();
    generateFriendsList();
}

// ===========================================================
// onStop
// ===========================================================

protected void onStop() {
    super.onStop();
}

// ===========================================================
// onDestroy
// ===========================================================

@Override
protected void onDestroy() {
    super.onDestroy();
}

// ===========================================================
// Activity methods
// ===========================================================

private void setButtonNewFriendClickListener() {
    Button clickButton = (Button)findViewById(R.id.button_add_friend);
    clickButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            Intent i = new Intent(v.getContext(), FriendNewActivity.class);
            startActivity(i);
        }
    });
}

The AndroidManifest looks like this

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  android:versionCode="1"
  android:versionName="1.0" package="com.package.mypackage">
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
    <activity android:name="com.package.mypackage.mypackage"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
     <activity android:name=".FriendsListActivity"></activity>
     <activity android:name=".FriendEditActivity"></activity>
     <activity android:name=".FriendNewActivity"></activity>
     <activity android:name=".TakePictureActivity"></activity>
     <activity android:name=".FriendsService"></activity>
     <activity android:name=".MyService"></activity>
</application>
<uses-sdk android:minSdkVersion="9" />

The MAIN activity looks like this:

    package com.package.mypackage;

import java.util.ArrayList;

import com.package.domain.Domain;
import com.package.service.MyService;
import com.package.viewadapter.myImageAdapter;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemLongClickListener;
import android.widget.Button;
import android.widget.Gallery;
import android.widget.Toast;

public class myActivity extends Activity {

// ===========================================================
// Fields
// ===========================================================

private MyImageAdapter myImageAdapter;
private ArrayList<Domain> domain = new ArrayList<Domain>();

// ===========================================================
// onCreate
// ===========================================================

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.main);

    /* Set Buttons to listen for any click event. */
    setButtonFriendsClickListener();
    setButtonCameraClickListener();
    setButtonPreferencesClickListener();
}

// ===========================================================
// onStart
// ===========================================================

@Override
public void onStart() {
    super.onStart();

    /* Find the gallery defined in the main.xml */        
    Gallery g = (Gallery) findViewById(R.id.gallery);
    /* Show a Toast message when image is clicked */
    g.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
            MyImageAdapter image_ID = new MyImageAdapter(myActivity.this, position, null);
            if (image_ID.getItemId(position) == 0) {
                Toast test_toast = Toast.makeText(myActivity.this, "This is the New Image click", Toast.LENGTH_SHORT);
                test_toast.show();
            }
            else {
                Toast test_toast = Toast.makeText(myActivity.this, "The clicked image has image number " + image_ID.getItemId(position) + " in the imageadapter.", Toast.LENGTH_SHORT);
                test_toast.show();
            }
        }
    });

    g.setOnItemLongClickListener(new OnItemLongClickListener() {

        @Override
        public boolean onItemLongClick(AdapterView<?> parent, View v, int position, long id) {
            MyImageAdapter image_ID = new MyImageAdapter(myActivity.this, position, null);
            Toast test_toast = Toast.makeText(myActivity.this, "The long clicked image has image number " + image_ID.getItemId(position) + " in the imageadapter.", Toast.LENGTH_SHORT);
            test_toast.show();
            return true;
        }
    });
}

// ===========================================================
// onPause
// ===========================================================

protected void onPause() {
    super.onPause();
}

// ===========================================================
// onResume
// ===========================================================

protected void onResume() {
    super.onResume();
    generateMyGallery();
}

// ===========================================================
// onStop
// ===========================================================

protected void onStop() {
    super.onStop();
}

// ===========================================================
// onDestroy
// Is also called when user changes from horizontal
// to vertical orientation and back
// ===========================================================

@Override
protected void onDestroy() {
    super.onDestroy();
}

// ===========================================================
// Save and Restore UI states
// ===========================================================

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
}

protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
}

// ===========================================================
// Main Activity methods
// ===========================================================


public void generateMyGallery() {
    MyService cs = new MyService(this);
    domain = cs.getDomainList();

    // Add the new_image drawable to the ArrayList
    Domain d = new Domain();
    d.photoLocation = "drawable";
    d.photoName = "new_image";
    d.extra1 = "no_text";
    d.extra2 = "no_text";
    domain.add(0, d);

    myImageAdapter = new MyImageAdapter(this, R.layout.text_overlay_image_view, domain);

    /* Find the gallery defined in the main.xml */        
    Gallery g = (Gallery) findViewById(R.id.gallery);
    g.setSpacing(10);

    /* Apply a new (custom) ImageAdapter to it. */
    g.setAdapter(myImageAdapter);
    g.setSelection(1);
}

private void setButtonFriendsClickListener() {
    Button clickButton = (Button)findViewById(R.id.button_friends_list);
    clickButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            setContentView(R.layout.friends_list);

            Intent myIntent = new Intent(v.getContext(), FriendsListActivity.class);
            startActivity(myIntent);
        }
    });
}

private void setButtonCameraClickListener() {
    Button clickButton = (Button)findViewById(R.id.button_take_picture);
    clickButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            setContentView(R.layout.take_picture);

            Intent myIntent = new Intent(v.getContext(), TakePictureActivity.class);
            startActivity(myIntent);
        }
    });
}

private void setButtonPreferencesClickListener() {
    Button clickButton = (Button)findViewById(R.id.button_preferences);
    clickButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            Intent myIntent = new Intent(v.getContext(), MyPreferencesActivity.class);
            startActivity(myIntent);
        }
    });
    }
};

Anyone has an idea why the App crashes. Any help is much appreciated.

I did find out that, when I finish() the MAIN activity when I start the FriendListActivity and restart the MAIN activity when closing the FriendListActivity, that the crash does not occur. However, this basically restarts the App and that is not the intention.

Thanks all, I got the problem solved. This is what I did.
. When moving all gallery related actions to the onCreate, the creash didn't happen anymore. But then after returning to the MAIN activity, the activity wasn't shown.
. I then moved all the onCreate (except the super), the generateGallery, and the onStart() to the onResume. Now it works fine!