How do I do something when an animation finishes?

问题:

I have an ImageView that I use to show progress via an AnimationDrawable. When I want to show my progress spinner, I do this:

animDrawable.start();
ObjectAnimator.ofFloat(view, "alpha", 1.0f).setDuration(300).start();

When I want to hide the spinner, I do this:

ObjectAnimator.ofFloat(view, "alpha", 0.0f).setDuration(300).start();
animDrawable.stop();

However, this has the effect that the animation stops immediately. I would like it to stop only after the ObjectAnimator has completely faded to 0.0 alpha. Is there a way I can setup something along the lines of an "AnimationCompleted" callback?

回答1:

The more modern way of doing this is to use the ViewPropertyAnimator:

view.animate()
    .alpha(0f)
    .withEndAction(new Runnable() {
      @Override
      public void run() {
        // Do something.
      }
    })
    .start();

Or, if you're using RetroLambda:

view.animate()
    .alpha(0f)
    .withEndAction(() -> {
      // Do something.
    })
    .start();

回答2:

To your original question about the ObjectAnimator object you can set up an Animator.AnimatorListener object which defines several animation state callbacks. You want to override public void onAnimationEnd(Animator animation)

animation.addListener(new Animator.AnimatorListener() {
                @Override
                public void onAnimationStart(Animator animation) {

                }

                @Override
                public void onAnimationEnd(Animator animation) {
                    Toast.makeText(VideoEditorActivity.this, "animation ended", Toast.LENGTH_LONG).show();
                }

                @Override
                public void onAnimationCancel(Animator animation) {

                }

                @Override
                public void onAnimationRepeat(Animator animation) {

                }
            });

回答3:

With androidx you can use doOnEnd method which invoked when the animation has ended

val anim = ObjectAnimator.ofFloat(eva_image, View.TRANSLATION_Y, 0f, 500f)
anim.setDuration(500)
anim.doOnEnd { Toast.makeText(this, "Anim End", Toast.LENGTH_SHORT).show() }
anim.start()

回答4:

You could also look into postOnAnimation(Runnable)

Link to Docs: postOnAnimation(java.lang.Runnable)