question

Are these source nowhere available? Then I guess I will exclude these devices from Google Play, they just give me bad ratings.

Hi, I'm sorry, but we don't release the sources of our MediaController. Is there anything more you can tell us about when you see that error that might help us reproduce it?

I could post the complete stacktrace. I don't own such a device so I couldn't reproduce it. The MediaController is in a ViewPager maybe you are disposing some resources if the tab gets hidden and that causes the NPE if the tabs gets visible again? I receive crash reports from "Amazon KFOT" and "Amazon KFTT". If you like to try to reproduce it in my app I would let you know the name of the app on some private channel. java.lang.NullPointerException at android.widget.MediaController.show(MediaController.java:529) at xx.yy.view.ObservableMediaController.show(ObservableMediaController.java:48) at xx.yy.a.b.i.a(VideoFragment.java:731) at xx.yy.BaseFragmentMainActivity.a(BaseFragmentMainActivity.java:290) at xx.yy.a.b.a.a(DetailFragment.java:146) at xx.yy.a.b.g.onTabSelected(TabsAdapter.java:87) at com.android.internal.app.ActionBarImpl.selectTab(ActionBarImpl.java:518) at com.android.internal.app.ActionBarImpl.setSelectedNavigationItem(ActionBarImpl.java:312) at xx.yy.a.b.g.a_(TabsAdapter.java:69) at android.support.v4.view.ViewPager.a(ViewPager.java:565) at android.support.v4.view.ViewPager.a(ViewPager.java:549) at android.support.v4.view.ViewPager.onTouchEvent(ViewPager.java:2004) at android.view.View.dispatchTouchEvent(View.java:5570) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1951) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1712) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1957) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1726) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1957) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1726) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1957) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1726) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1957) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1726) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1957) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1726) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1957) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1726) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1957) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1726) at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2086) at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1544) at android.app.Activity.dispatchTouchEvent(Activity.java:2483) at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2033) at android.view.View.dispatchPointerEvent(View.java:5750) at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:2910) at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2486) at android.view.ViewRootImpl.processInputEvents(ViewRootImpl.java:853) at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2495) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4532) 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:784) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) at dalvik.system.NativeStart.main(Native Method)

As a correction, I was actually incorrect about the sources comment, you can find that here: http://www.amazon.com/gp/help/customer/display.html?nodeId=200203720

Do you know which version of FireOS your device is running?