@Override
public void onResume() {
super.onResume();
startBackgroundThread();
// When the screen is turned off and turned back on, the SurfaceTexture is already
// available, and "onSurfaceTextureAvailable" will not be called. In that case, we can open
// a camera and start preview from here (otherwise, we wait until the surface is ready in
// the SurfaceTextureListener).
if (mTextureView.isAvailable()) {
openCamera(mTextureView.getWidth(), mTextureView.getHeight());
} else {
mTextureView.setSurfaceTextureListener(mSurfaceTextureListener);
}
}