如何实现整个翻译动画均匀的速度？ [英] How to achieve uniform velocity throughout a Translate Animation?

问题描述

我已经申请到一个无限的翻译动画的ImageView ：

I have an infinite translate animation applied to an ImageView:

Animation animation = new TranslateAnimation(0, 0, -500, 500);
animation.setDuration(4000);
animation.setFillAfter(false);
myimage.startAnimation(animation);
animation.setRepeatCount(Animation.INFINITE);

我所注意到的是，在翻译过程是当图像是接近的起始和结束点时相比，其接近一半的距离（中间点）更慢。

What I have noticed is that the translation process is slower when the image is near the starting and ending point compared to when its near half the distance (middle point).

我想在Android上的不统一翻译动画的速度。

I guess the velocity for translate animations on android is not uniform.

如何让我的速度均匀的整个过程？

How do I make the velocity uniform throughout the process ?

推荐答案

我做了一些源潜水进行调查。首先，注意的如果的的线性插值是用来提供 interpolatedTime 值到 applyTransformation 的<方法href=\"https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/core/java/android/view/animation/TranslateAnimation.java\"相对=nofollow> TranslateAnimation ，由此产生的翻译将有恒定的速度（因为偏移 DX 和 DY 是 interpolatedTime 的线性函数（线149-160））：

I did some source-diving to investigate this. First, note that if a linear interpolator is used to provide interpolatedTime values to the applyTransformation method of TranslateAnimation, the resulting translation will have constant velocity (because the offsets dx and dy are linear functions of interpolatedTime (lines 149-160)):

@Override
protected void applyTransformation(float interpolatedTime, Transformation t) {
    float dx = mFromXDelta;
    float dy = mFromYDelta;
    if (mFromXDelta != mToXDelta) {
        dx = mFromXDelta + ((mToXDelta - mFromXDelta) * interpolatedTime);
    }
    if (mFromYDelta != mToYDelta) {
        dy = mFromYDelta + ((mToYDelta - mFromYDelta) * interpolatedTime);
    }
    t.getMatrix().setTranslate(dx, dy);
}

applyTransformation 由基 getTransformation 方法调用href=\"https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/core/java/android/view/animation/Animation.java\"相对=nofollow> 动画 类（行869-870）：

applyTransformation is called by the getTransformation method of the base Animation class (lines 869-870):

...
final float interpolatedTime = mInterpolator.getInterpolation(normalizedTime);
applyTransformation(interpolatedTime, outTransformation);
...

据为 setInterpolator 办法（线382-392）的文件， mInterpolator 应该默认为线性内插器：

According to the documentation for the setInterpolator method (lines 382-392), mInterpolator should default to a linear interpolator:

/**
 * Sets the acceleration curve for this animation. Defaults to a linear
 * interpolation.
 *
 * @param i The interpolator which defines the acceleration curve
 * @attr ref android.R.styleable#Animation_interpolator
 */
public void setInterpolator(Interpolator i) {
    mInterpolator = i;
}

不过，这似乎是错误的：在动画类调用两个构造的 ensureInterpolator 办法（行803 -811）：

However, this seems to be false: both constructors in the Animation class call the ensureInterpolator method (lines 803-811):

/**
 * Gurantees that this animation has an interpolator. Will use
 * a AccelerateDecelerateInterpolator is nothing else was specified.
 */
protected void ensureInterpolator() {
    if (mInterpolator == null) {
        mInterpolator = new AccelerateDecelerateInterpolator();
    }
}

这表明缺省插入是 AccelerateDecelerateInterpolator 。这说明你在你的问题描述的行为。

which suggests that the default interpolator is an AccelerateDecelerateInterpolator. This explains the behavior you describe in your question.

要真正回答你的问题，那么，这样看来，你应该修改你的code如下：

To actually answer your question, then, it would appear that you should amend your code as follows:

Animation animation = new TranslateAnimation(0, 0, -500, 500);
animation.setInterpolator(new LinearInterpolator());
animation.setDuration(4000);
animation.setFillAfter(false);
myimage.startAnimation(animation);
animation.setRepeatCount(Animation.INFINITE);

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