Android Color颜色过度计算实现代码

android color颜色过度计算实现代码

在看自定义typeevaluator来计算属性动画的属性值时，用到了对颜色的过度计算，翻看了好多博客，找到了比较有优秀的解决方案，在此记录，以备后用。

实现效果图：

实现代码：

/**
 * 根据fraction值来计算当前的颜色。
 */
private int getcurrentcolor(float fraction, int startcolor, int endcolor) {
  int redcurrent;
  int bluecurrent;
  int greencurrent;
  int alphacurrent;

  int redstart = color.red(startcolor);
  int bluestart = color.blue(startcolor);
  int greenstart = color.green(startcolor);
  int alphastart = color.alpha(startcolor);

  int redend = color.red(endcolor);
  int blueend = color.blue(endcolor);
  int greenend = color.green(endcolor);
  int alphaend = color.alpha(endcolor);

  int reddifference = redend - redstart;
  int bluedifference = blueend - bluestart;
  int greendifference = greenend - greenstart;
  int alphadifference = alphaend - alphastart;

  redcurrent = (int) (redstart + fraction * reddifference);
  bluecurrent = (int) (bluestart + fraction * bluedifference);
  greencurrent = (int) (greenstart + fraction * greendifference);
  alphacurrent = (int) (alphastart + fraction * alphadifference);

  return color.argb(alphacurrent, redcurrent, greencurrent, bluecurrent);
}

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