Android - AnimatorSet, Object Animator - Bounce an

问题:

I have a question concerning ObjectAnimator in Android. I am trying to model a Bounce effect whereby the View slides up (decreasing Y value) and back down after by the same amount 'n', followed by the View sliding up and down again but this time by 'n/2' (so half the distance).

So a bigger bounce, followed by a shallower bounce - i.e., the kinda thing a Mac icon does in the tray when it wants your attention.

Here is what I've tried so far (assume v is a View):

float y = v.getTranslationY(),distance = 20F;

                AnimatorSet s = new AnimatorSet();
                s.play(ObjectAnimator.ofFloat(v, "translationY", y- distance).setDuration(500))
                .before(ObjectAnimator.ofFloat(v, "translationY", y).setDuration(500))
                .before(ObjectAnimator.ofFloat(v, "translationY", y- (distance/2)).setDuration(500))
                .before(ObjectAnimator.ofFloat(v, "translationY", y).setDuration(500));
                s.start();

Ignore the code quality, it's a POC! I was hoping this would work, but it seems to only 'bounce' once as if its combined the animations despite the use of .before().

Could you please show me how I can create complex AnimatorSet chains that do not amalgamate in to one, as I seem to be missing something?

BONUS: For extra points, how can I set the repeat of an AnimatorSet?

Many thanks!

回答1:

OK so I eventually found a fairly neat way to achieve sequential animation by ignoring the fluent builder, and just using the playSequentially() method such that:

AnimatorSet as = new AnimatorSet();
as.playSequentially(ObjectAnimator.ofFloat(...), // anim 1
                    ObjectAnimator.ofFloat(...), // anim 2
                    ObjectAnimator.ofFloat(...), // anim 3
                    ObjectAnimator.ofFloat(...)); // anim 4
as.setDuration(600);
as.start();

Still haven't worked out repeating though, other than a dirty hack involving the callback onAnimationEnd in a listener. Must be a simpler way, so perhaps someone can edit this when they know of one.

Anyway, hope the above helps someone.

回答2:

When you use the Builder, all returning dependencies refer to the first Animator, so you had 3 bounces happening simultaneously after the first movement. Unfortunately it seems AnimatorSet is broken on some aspects, one of them being repeats : https://code.google.com/p/android/issues/detail?id=17662