I have a problem during runtime of my Android widget with Android 2.3.3 and older. When i install my widget on the screen, this error is printed : 11-03 10:26:31.127: E/AndroidRuntime(404): FATAL EXCEPTION: main 11-03 10:26:31.127: E/AndroidRuntime(404): java.lang.NoClassDefFoundError: com.app.myapp.StackWidgetService 11-03 10:26:31.127: E/AndroidRuntime(404): at com.app.myapp.StackWidgetProvider.onUpdate(StackWidgetProvider.java:229) 11-03 10:26:31.127: E/AndroidRuntime(404): at android.appwidget.AppWidgetProvider.onReceive(AppWidgetProvider.java:61) 11-03 10:26:31.127: E/AndroidRuntime(404): at com.app.mobideals.StackWidgetProvider.onReceive(StackWidgetProvider.java:216) 11-03 10:26:31.127: E/AndroidRuntime(404): at android.app.ActivityThread.handleReceiver(ActivityThread.java:1794) 11-03 10:26:31.127: E/AndroidRuntime(404): at android.app.ActivityThread.access$2400(ActivityThread.java:117) 11-03 10:26:31.127: E/AndroidRuntime(404): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:981) 11-03 10:26:31.127: E/AndroidRuntime(404): at android.os.Handler.dispatchMessage(Handler.java:99) 11-03 10:26:31.127: E/AndroidRuntime(404): at android.os.Looper.loop(Looper.java:123) 11-03 10:26:31.127: E/AndroidRuntime(404): at android.app.ActivityThread.main(ActivityThread.java:3683) 11-03 10:26:31.127: E/AndroidRuntime(404): at java.lang.reflect.Method.invokeNative(Native Method) 11-03 10:26:31.127: E/AndroidRuntime(404): at java.lang.reflect.Method.invoke(Method.java:507) 11-03 10:26:31.127: E/AndroidRuntime(404): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 11-03 10:26:31.127: E/AndroidRuntime(404): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 11-03 10:26:31.127: E/AndroidRuntime(404): at dalvik.system.NativeStart.main(Native Method) The problem is due to the fact that the compilator don't arrive to perform the link to the StackWidgetService class at this line in onUpdate method of StackWidgetProvider class : public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) { // update each of the widgets with the remote adapter for (int i = 0; i < appWidgetIds.length; ++i) { // Here we setup the intent which points to the StackViewService which will // provide the views for this collection. Intent intent = new Intent(context, StackWidgetService.class); intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetIds[i]); The widget works well with other version of Android like 3.0, 4.0 etc... Please help me :)