Question

I have to animate a circular count down timer and I’m doing it by animating the background of an ImageView using AnimationDrawable (each image has the according slice of the circle removed). The problem is that the user has the ability to pause this animation, so I have to reload the animation but then a problem appears. I’ve tried setting the the animation to null, setting the background of the ImageView to null, setting the visibility of the animation, but practically nothing helped, because number of frames remains the same. I have to find a workaround for deleting all frames and adding new ones or to reset the whole animation to the default state.

Step 1 – initializing the animation (starting frame index is 0)

timerView.setBackgroundResource(R.drawable.timer_switch);
timerAnimation = (AnimationDrawable)timerView.getBackground();

System.out.println("Number of frames: " + timerAnimation.getNumberOfFrames());

for (int frameIndex = startingFrameIndex; frameIndex < 60; frameIndex++) {
    if (frameIndex < 10) {
        uri = "drawable/timer_0000" + frameIndex;
    } else {
        uri = "drawable/timer_000" + frameIndex;
    }

    imageResourceId = getResources().getIdentifier(uri, null, getPackageName());
    timerAnimation.addFrame(getResources().getDrawable(imageResourceId), timerImageFrameDuration);
}

Step 2 – here’s the tricky part where I don’t know what to do. Things that I’ve tried:

timerAnimation.stop();
timerAnimation.setCallback(null);
timerAnimation.setVisibility(true, false);
timerAnimation = null;

Step 3 – after calling step 2 I call step 1 again, but the Sys.out still displays 60 as the current number of frames. (starting index here is set to the last hidden frame when pause button was tapped.)

Any idea is welcomed.

Thanks

Answer 1

I had the same problem where stopping the animation would stop on the current frame. I wanted it to behave like iOS, where stopping would go back to the first frame. This solution works for me:

((AnimationDrawable)(someButton.getBackground())).stop();
someButton.setBackgroundDrawable(null);
someButton.setBackgroundResource(R.drawable.animation);

This first stops it (probably not necessary). Then it kills the background animation. Finally, it recreates the background.