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PONullPointerException when adding/removing views of a RelativeLayout (Animations)
 

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  1. PONullPointerException when adding/removing views of a RelativeLayout (Animations)
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    <p>Hi I want to create a Image and animate from bottom to top and change the alpha from 1.0 to 0.0. I have this code (I call 3 times in onCreate method to make 3 animated images):</p> <pre><code>/** * Starts to make fog */ private void startFogGenerator() { handler.postDelayed(new Runnable() { @Override public void run() { final ImageView img = new ImageView(Activity.this); boolean showN1 = r.nextBoolean(); if (showN1) { img.setImageResource(R.drawable.nube_01); } else { img.setImageResource(R.drawable.nube_02); } Animation animation = AnimationUtils.loadAnimation(Activity.this, R.anim.translate_and_alpha); animation.setAnimationListener(new Animation.AnimationListener() { @Override public void onAnimationStart(Animation animation) { } @Override public void onAnimationEnd(Animation animation) { fogLayout.removeView(img); fogLayout.invalidate(); // always true? Maybe but just check for for concurrency safe. if (setFogN(false) &lt; MAX_CLOUDS_ON_SCREEN) { startFogGenerator(); } } @Override public void onAnimationRepeat(Animation animation) { } }); int pxWidth = Tools.toPx(140, getResources()); // Width of layout container int paddingWidth = Tools.toPx(20, getResources()); int x = r.nextInt(pxWidth - paddingWidth - paddingWidth) + paddingWidth; int range = Tools.toPx(50, getResources()); int width; int height; if (showN1) { // nube01: 167x226 width = r.nextInt(Tools.toPx(167, getResources()) - range) + range; height= r.nextInt(Tools.toPx(226, getResources()) - range) + range; } else { // nube01: 144x177 width = r.nextInt(Tools.toPx(144, getResources()) - range) + range; height= r.nextInt(Tools.toPx(177, getResources()) - range) + range; } Log.d("Animation", "X: " + x + ", Width: " + width + ", Height: " + height); //img.setPadding(x, 0, 0, 0); RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(width, height); params.leftMargin = x; fogLayout.addView(img, params); img.setBackgroundColor(Color.argb(255, r.nextInt(255),r.nextInt(255),r.nextInt(255))); // just for debug img.startAnimation(animation); setFogN(true); } }, r.nextInt(2500 - 200) + 200); } private final static int MAX_CLOUDS_ON_SCREEN = 3; private AtomicInteger currentFogs = new AtomicInteger(0); private synchronized int setFogN(boolean increment) { int toReturn = increment ? currentFogs.incrementAndGet() : currentFogs.decrementAndGet(); Log.d("TeaAnim", "ToReturn: "+ toReturn); return toReturn; } </code></pre> <p>Works ok but when removes the 3th view and starts another time, it crashes with NullPointerException, maybe is problem of concurrency? How I can fix it?</p> <p>Exception:</p> <pre><code>ERROR/AndroidRuntime(10736): FATAL EXCEPTION: main java.lang.NullPointerException at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2796) at android.view.View.getDisplayList(View.java:12648) at android.view.View.getDisplayList(View.java:12694) at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:2910) at android.view.View.getDisplayList(View.java:12588) at android.view.View.getDisplayList(View.java:12694) at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:2910) at android.view.View.getDisplayList(View.java:12588) at android.view.View.getDisplayList(View.java:12694) at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:2910) at android.view.View.getDisplayList(View.java:12588) at android.view.View.getDisplayList(View.java:12694) at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:2910) at android.view.View.getDisplayList(View.java:12588) at android.view.View.getDisplayList(View.java:12694) at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:2910) at android.view.View.getDisplayList(View.java:12588) at android.view.View.getDisplayList(View.java:12694) at android.view.HardwareRenderer$GlRenderer.draw(HardwareRenderer.java:1198) at android.view.ViewRootImpl.draw(ViewRootImpl.java:2173) at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2045) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1854) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749) at android.view.Choreographer.doCallbacks(Choreographer.java:562) at android.view.Choreographer.doFrame(Choreographer.java:532) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735) at android.os.Handler.handleCallback(Handler.java:725) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5204) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:799) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566) at dalvik.system.NativeStart.main(Native Method) </code></pre> <p>Notes: fogLayout is a RelativeLayout with a fixed width and height (in dp) Tools.toPx is a method that coverts from DP to PX</p>
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