EnterTransitionCoordinator causes NPE in Android 5.0

Question

After adding exit and enter Activity transitions to an app, I am getting crash reports like the following:

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewParent android.view.View.getParent()' on a null object reference at android.view.ViewOverlay$OverlayViewGroup.add(ViewOverlay.java:164) at android.view.ViewGroupOverlay.add(ViewGroupOverlay.java:63) at android.app.EnterTransitionCoordinator.startRejectedAnimations(EnterTransitionCoordinator.java:598) at android.app.EnterTransitionCoordinator.startSharedElementTransition(EnterTransitionCoordinator.java:325) at android.app.EnterTransitionCoordinator.access$200(EnterTransitionCoordinator.java:42) at android.app.EnterTransitionCoordinator$5$1.run(EnterTransitionCoordinator.java:389) at android.app.ActivityTransitionCoordinator.startTransition(ActivityTransitionCoordinator.java:698) at android.app.EnterTransitionCoordinator$5.onPreDraw(EnterTransitionCoordinator.java:386) at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:847) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1985) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1077) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5845) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767) at android.view.Choreographer.doCallbacks(Choreographer.java:580) at android.view.Choreographer.doFrame(Choreographer.java:550) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5272) at java.lang.reflect.Method.invoke(Method.java) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:909) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:704)

It's not reproducible, but the crash count is significant.

Doing some research, I came across this commit suggesting it is (was actually) an internal error in Android: https://android.googlesource.com/platform/frameworks/base/+/83c692efd3c53050fce132dfd2ef21763d3cf010%5E%21/#F0

All crash reports are either 5.0, 5.0.1, or 5.0.2. Because 5.1 has wider spread, but does not show crashes, it seems like EnterTransitionCoordinator was fixed in 5.1.

So, a possible solution would be to check for API level 22 or higher, and only do the transitions then. However I wonder if there's a better way; some workaround maybe, despite this seems to be an internal matter of Android (all system classes in the stack)?

Answer 1

After requiring API level 22 (Android 5.1) for transition, the crashes are gone. So this is the most simple solution. If you need to support this with Android 5.0, check Nikola's answer (we did not try it ourselves to avoid additional code).