android - 如何停止动画(来自 ObjectAnimator)

Question

下面是属于我的 Activity 的代码，其中我有一个按钮 (someButton)，单击该按钮时，会在同一 Activity 的另一个 View 上启动动画，更具体地说，是一个进度条 View :

// [...]
someButton.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {
        ObjectAnimator animation = ObjectAnimator.ofInt(progressView, "progress", 0, 2000);
        animation.setDuration(2000);
        animation.setInterpolator(new DecelerateInterpolator());
        animation.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                // some code to execute when the animation ends
            }
        });
        animation.start();
    }
});
// [...]

现在，在某些时候我可能需要停止该进度条 View 的动画(例如，当用户点击停止按钮时)。我调用了 progressView.clearAnimation() 来停止动画但没有成功。我还注意到 progressView.getAnimation() 返回 null ... 当我将 ObjectAnimator animation 变量设置为 final 并将其移到 someButton.setOnClickListener 之外，以便稍后访问它以停止动画时，我得到以下异常点击 someButton(就像发生的事情 here ):

java.lang.NullPointerException
   at android.animation.PropertyValuesHolder.setupSetterAndGetter(PropertyValuesHolder.java:505)
   at android.animation.ObjectAnimator.initAnimation(ObjectAnimator.java:487)
   at android.animation.ValueAnimator.setCurrentPlayTime(ValueAnimator.java:517)
   at android.animation.ValueAnimator.start(ValueAnimator.java:936)
   at android.animation.ValueAnimator.start(ValueAnimator.java:946)
   at android.animation.ObjectAnimator.start(ObjectAnimator.java:465)
   at android.animation.AnimatorSet$1.onAnimationEnd(AnimatorSet.java:579)
   at android.animation.ValueAnimator.endAnimation(ValueAnimator.java:1056)
   at android.animation.ValueAnimator.access$400(ValueAnimator.java:50)
[...]

抛出该异常的代码是:

// [...]

final ObjectAnimator animation = ObjectAnimator.ofInt(progressView, "progress", 0, 2000);
animation.setDuration(2000);
animation.setInterpolator(new DecelerateInterpolator());
animation.addListener(new AnimatorListenerAdapter() {
    @Override
    public void onAnimationEnd(Animator animation) {
        // some code to execute when the animation ends
    }
});

someButton.setOnClickListener(new OnClickListener() {
    public void onClick(View v) {
        animation.start();// NPE occurs here!
    }
});
// [...]

这里有什么问题？？怎么才能停止那个动画呢？？？

Answer 1

你可以这样使用:

valueAnimator?.removeAllUpdateListeners()
valueAnimator?.removeAllListeners()
valueAnimator?.end()
valueAnimator?.cancel()
valueAnimator = null