ValueAnimator设置时长无效

最新推荐文章于 2024-11-14 15:46:16 发布

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本文解决了一个问题，在某些安卓设备上，属性动画会异常地瞬间从起点跳到终点。通过调试发现这是由于系统动画时长缩放设置导致的问题，并提供了解决方案。

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转载:https://blog.youkuaiyun.com/u011387817/article/details/78628956

今天在低端机上面测试，发现里面的属性动画竟然无法正常播放, 一下子就从起点跳到终点。

一番调试无果后，就感觉是手机本身问题，于是就想看看其他应用的属性动画在这台手机上是否也这样：

记得之开布局边界时，看到网易云音乐客户端的音乐播放界面中的光盘旋转效果是属性动画，于是打开应用后，随便播放一首歌，发现光盘果然是不转了，这时忽然想到设置-开发者选项中有几个动画时长缩放的选项，打开一看，原来是 “动画程序时长缩放” 这个选项选择了关闭动画，重新打开后果然恢复正常了。

但是实际应用中总不能提示用户手动开启吧，究竟设置中的这个选项是怎样影响到我们应用中的动画时长的呢。

还是先说解决方法吧：(经测试，每次在activity recreate后都会重置动画时长为系统指定的值，哈哈，所以如果想偷懒,只在Application onCreate里面调用下面的方法的话，依然是不起作用的，建议每次播放动画前重置一下。)

public class ValueAnimatorUtil {

    /**
     * 如果动画被禁用，则重置动画缩放时长
     */
    public static void resetDurationScaleIfDisable() {
        if (getDurationScale() == 0)
            resetDurationScale();
    }

    /**
     * 重置动画缩放时长
     */
    public static void resetDurationScale() {
        try {
            getField().setFloat(null, 1);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static float getDurationScale() {
        try {
            return getField().getFloat(null);
        } catch (Exception e) {
            e.printStackTrace();
            return -1;
        }
    }

    @NonNull
    private static Field getField() throws NoSuchFieldException {
        Field field = ValueAnimator.class.getDeclaredField("sDurationScale");
        field.setAccessible(true);
        return field;
    }
}

下面说说原因：
打开ValueAnimator源码,看到一个私有的静态变量 sDurationScale:

public class ValueAnimator extends Animator implements AnimationHandler.AnimationFrameCallback {
    private static final String TAG = "ValueAnimator";
    private static final boolean DEBUG = false;

    /**
     * Internal constants
     */
    private static float sDurationScale = 1.0f;

难道是这个东西在作怪？看看下面的方法：
这个方法是处理动画帧的方法，更新了mLastFrameTime后，判断动画是否已经播放完毕，
如果播放完毕，就进行结束动画的一系列处理：回调接口、重置状态等

  /**
     * Processes a frame of the animation, adjusting the start time if needed.
     *
     * @param frameTime The frame time.
     * @return true if the animation has ended.
     * @hide
     */
    public final boolean doAnimationFrame(long frameTime) {
       ....
       ....

       mLastFrameTime = frameTime;
       final long currentTime = Math.max(frameTime, mStartTime);

       boolean finished = animateBasedOnTime(currentTime);
       if (finished) {
       endAnimation();
       } 
       return finished;
    }

我们来看看他是怎样判断动画是否播放完毕的：
这次我们要关注的是getScaledDuration这个方法，因为这个方法返回的值能决定是否播放完毕

    boolean animateBasedOnTime(long currentTime) {
        boolean done = false;
        if (mRunning) {
            final long scaledDuration = getScaledDuration();
            final float fraction = scaledDuration > 0 ?
                    (float)(currentTime - mStartTime) / scaledDuration : 1f;
            final float lastFraction = mOverallFraction;
            final boolean newIteration = (int) fraction > (int) lastFraction;
            final boolean lastIterationFinished = (fraction >= mRepeatCount + 1) &&
                    (mRepeatCount != INFINITE);
            if (scaledDuration == 0) {
                // 0 duration animator, ignore the repeat count and skip to the end
                done = true;
            } else if (newIteration && !lastIterationFinished) {
                // Time to repeat
                if (mListeners != null) {
                    int numListeners = mListeners.size();
                    for (int i = 0; i < numListeners; ++i) {
                        mListeners.get(i).onAnimationRepeat(this);
                    }
                }
            } else if (lastIterationFinished) {
                done = true;
            }
            mOverallFraction = clampFraction(fraction);
            float currentIterationFraction = getCurrentIterationFraction(
                    mOverallFraction, mReversing);
            animateValue(currentIterationFraction);
        }
        return done;
    }

getScaledDuration方法：
是用我们设定的动画时长 * mDurationScale, 如果mDurationScale为0，那么就满足上面的条件，直接认为动画播放完毕了

 private long getScaledDuration() {
        return (long)(mDuration * sDurationScale);
    }

下面我们来验证一下设置-开发者选项-动画时长缩放这个选项是否跟mDurationScale有关：

      try {
            Field field = ValueAnimator.class.getDeclaredField("sDurationScale");
            field.setAccessible(true);
            LogUtil.print(field.getFloat(null));
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }

先是默认的：
这里写图片描述
日志输出：

1.0

再试试5x的：
这里写图片描述
日志输出：

5.0

没错了，最后试试关闭动画：
这里写图片描述
日志输出果然是0.0。我们再播放一个ValueAnimator来测试下：

     ValueAnimator animator = ValueAnimator.ofInt(0, 100).setDuration(1000);
     animator.addUpdateListener(animation -> LogUtil.print(animation.getAnimatedValue()));
     animator.start();

输出：

11-24 21:22:59.925 9244-9244/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 0
11-24 21:23:00.087 9244-9244/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 100

输出0之后，直接是100了，这就对应了开头描述的情况:一下子就从起点跳到终点。

最后我们试试在动画开始前重置mDurationScale:

     ValueAnimator animator = ValueAnimator.ofInt(0, 100).setDuration(1000);
      animator.addUpdateListener(animation -> LogUtil.print(animation.getAnimatedValue()));
      ValueAnimatorUtil.resetDurationScale();
      animator.start();

输出：

11-24 21:30:35.102 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 0
11-24 21:30:35.261 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 0
11-24 21:30:35.332 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 1
11-24 21:30:35.393 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 5
11-24 21:30:35.406 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 6
11-24 21:30:35.424 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 7
11-24 21:30:35.442 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 9
11-24 21:30:35.460 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 11
11-24 21:30:35.478 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 13
11-24 21:30:35.496 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 14
11-24 21:30:35.515 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 17
11-24 21:30:35.534 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 19
11-24 21:30:35.551 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 21
11-24 21:30:35.569 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 24
11-24 21:30:35.587 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 26
11-24 21:30:35.605 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 28
11-24 21:30:35.623 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 31
11-24 21:30:35.641 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 34
11-24 21:30:35.659 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 36
11-24 21:30:35.677 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 39
11-24 21:30:35.696 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 42
11-24 21:30:35.713 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 45
11-24 21:30:35.732 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 48
11-24 21:30:35.750 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 51
11-24 21:30:35.768 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 53
11-24 21:30:35.786 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 56
11-24 21:30:35.804 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 59
11-24 21:30:35.822 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 62
11-24 21:30:35.840 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 65
11-24 21:30:35.858 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 67
11-24 21:30:35.877 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 70
11-24 21:30:35.895 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 72
11-24 21:30:35.913 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 75
11-24 21:30:35.931 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 77
11-24 21:30:35.951 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 80
11-24 21:30:35.969 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 82
11-24 21:30:35.987 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 84
11-24 21:30:36.004 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 86
11-24 21:30:36.022 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 88
11-24 21:30:36.040 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 90
11-24 21:30:36.058 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 91
11-24 21:30:36.076 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 93
11-24 21:30:36.095 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 94
11-24 21:30:36.112 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 95
11-24 21:30:36.130 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 96
11-24 21:30:36.148 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 97
11-24 21:30:36.167 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 98
11-24 21:30:36.185 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 99
11-24 21:30:36.203 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 99
11-24 21:30:36.221 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 99
11-24 21:30:36.239 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: 99
11-24 21:30:36.257 12224-12224/com.test E/com.test.TestActivity-->lambda$onCreate$0$TestActivity: