Android ViewGroup crash: Attempt to read from field 'int android.view.View.mViewFlags' on a null object reference

Possible Solution

I had this same issue. I setup an animation and in onAnimationEnd I was removing the object that had been animated which is when problems started. What I did was setup an asynchronous Runnable to wait 100 milliseconds after the animation had stopped before removing the animated object:

the object previously animated is this._loader

private void removeLoader() {
    final ContentContainer self = this; // "CustomContainer" needs to match the type of `this`
    Handler h = new Handler();
    h.postAtTime(new Runnable() {
        @Override
        public void run() {
            MainActivity.instance.runOnUiThread(new Runnable() { 
                @Override
                public void run() {
                    try {
                        if(self._loader == null) {
                            // there is no loader. quit now while you still have the chance!!
                            return;
                        }
                        while(self._loader.getParent() != null) {
                            removeView(self._loader);
                        }
                    } catch(Exception e) {
                        Crashlytics.logException(e);
                        e.printStackTrace();
                    }

                    self._loader = null;
                }
            });
        }
    }, 100);
}

Cheers

I was facing same problem. I resolved with Handler.

new Handler(Looper.getMainLooper()).post(new Runnable() {
                @Override
                public void run() {
                   // remove fragment from here
                }
            });