When the TextureView loses visibility (either because the screen is rotated, other Activity comes to the front or you press the Home button) it nullifies its SurfaceTexture.OnFrameAvailableListener (on GrepCode). It looks like when this happens and at that very moment the Canvas instance is executing drawX() methods natively on C++ code the app will crash because for some reason the memory containing that canvas is cleared before the method is finished. However, because Canvas.drawX() methods make use of Android native C++ code, C++ doesn't throw a NullPointerException (How to catch the null pointer exception?) and hence the Java exception handling system is in this case useless.
This issue renders unusable the TextureView class as long as you call drawX() methods more than a bunch of times or you draw some complex stuff on the Canvas.
Pretty much like a bug on threading and/or on the C++ code side. I've opened an issue reporting this: https://code.google.com/p/android/issues/detail?id=85380.
EDIT: I've found a reliable way to avoid calling drawX() methods when the TextureView isn't visible any more and hence the app starts crashing: interrupt the thread that is drawing on the Canvas and check before every call to any drawX() method that the thread is interrupted. Prior onPause() is called drawX() methods won't throw any error.
mThread = new Thread() {
@Override
public void run() {
Canvas canvas = mTV.lockCanvas();
/** Draw your stuff on the canvas but check before every
single drawX() call whether mThread has been interrupted **/
Paint p = new Paint();
p.setColor(Color.RED);
for (int n=0; n<5000; ++n) {
if (mThread.isInterrupted())
break;
canvas.drawCircle(0, 0, 300, p);
}
/** **/
mTV.unlockCanvasAndPost(canvas);
};
mThread.start();
And then on onPause() –just the moment before when calling Canvas.drawX() will start to crash the app– interrupt the thread:
@Override
public void onPause() {
super.onPause();
if (mThread != null) {
mThread.interrupt();
mThread = null;
}
}
Add also the same code to onStop() and to onDestroy(). I've also tried to use the TextureView.onVisibilityChanged() method by overriding it to interrupt the thread. But this method is invoked almost 500 ms after onPause() is called when it's too late and drawX() calls start to crash the app.
