Android-动画视图中的getAlpha（） [英] Android - getAlpha() from Animated View

问题描述

我有一个这样的动画：

Animation fadeOut = new AlphaAnimation(1, 0);
fadeOut.setInterpolator(new DecelerateInterpolator());
fadeOut.setDuration(350);
myView.startAnimation(fadeOut);

我正在尝试让其Alpha在动画中如此播放：

I am trying is to get its Alpha durring the Animation as such:

System.out.println(myView.getAlpha());

但是，在整个动画中始终返回 1.0。如何在动画过程中获取 myView 的实际Alpha值？

However, it always returns "1.0" throughout the animation. How can I obtain the actual alpha value of myView during the animation process?

推荐答案

通过将 Transformation 与 AlphaAnimation 结合使用，您可能可以直接从 AlphaAnimation 对象而不是您的 View 。

By using Transformation with your AlphaAnimation, you may be able to retrieve alpha value directly from your AlphaAnimation object instead of your View.

使用Transformation的目的：

Purpose of using Transformation:

定义要在动画的某个时间点应用的变换。

Defines the transformation to be applied at one point in time of an Animation.

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步骤：

1. 创建一个新的 Transformation.java 类，如 https://sourcegraph.com/android.googlesource.com/platform/frameworks/base/-//blob /core/java/android/view/animation/Transformation.java 。

初始化 Transformation 对象：

private Transformation myTransformation;
mTransformation = new Transformation();

使用您的代码：

Using your code:

Animation fadeOut = new AlphaAnimation(1, 0);
fadeOut.setInterpolator(new DecelerateInterpolator());
fadeOut.setDuration(350);

获取视图层次结构开始绘制的时间（以毫秒为单位）：

Get the time at which the drawing of the view hierarchy started (in milliseconds):

final long time = myView.getDrawingTime();

获取转换以在指定的时间点应用。最后，获得动画过程中的实际Alpha值：

Get the transformation to apply at a specified point in time. Finally, obtain the actual alpha value during the animation:

fadeOut.getTransformation(time, myTransformation);
final float myAlphaValue = myTransformation.getAlpha();

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资源：
https://sourcegraph.com/android.googlesource.com/platform/frameworks/base/-/blob/core/java/android/widget/ProgressBar.java# L1699
https://developer.android。 com / reference / android / view / animation / Animation.html
https://developer.android.com/reference/android/view/animation/Transformation.html

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