下面示例为view的背景色在3s内从透明度100%的红色到透明度为60%的绿色进行过渡变化,此处view和为任何View
ValueAnimator animator = ObjectAnimator.ofInt(view, "backgroundColor", 0x00ff0000, 0x6600ff00);//对背景色颜色进行改变,操作的属性为"backgroundColor",此处必须这样写,不能全小写,后面的颜色为在对应颜色间进行渐变
animator.setDuration(3000);
animator.setEvaluator(new ArgbEvaluator());//如果要颜色渐变必须要ArgbEvaluator,来实现颜色之间的平滑变化,否则会出现颜色不规则跳动
animator.start();
ArgbEvaluator
/**
*颜色演变核心算法
* fraction:动画过渡时间因子,决定了动画变化的速率,值为0-1之间
* startvalue:动画起始颜色
* endValue:动画结束颜色
*/
public Object evaluate(float fraction, Object startValue, Object endValue) {
int startInt = (Integer) startValue;
/*
* 起始颜色ARGB颜色通道拆分
*/
float startA = ((startInt >> 24) & 0xff) / 255.0f;
float startR = ((startInt >> 16) & 0xff) / 255.0f;
float startG = ((startInt >> 8) & 0xff) / 255.0f;
float startB = ( startInt & 0xff) / 255.0f;
/*
* 结束颜色ARGB颜色通道拆分
*/
int endInt = (Integer) endValue;
float endA = ((endInt >> 24) & 0xff) / 255.0f;
float endR = ((endInt >> 16) & 0xff) / 255.0f;
float endG = ((endInt >> 8) & 0xff) / 255.0f;
float endB = ( endInt & 0xff) / 255.0f;
// convert from sRGB to linear
startR = (float) Math.pow(startR, 2.2);
startG = (float) Math.pow(startG, 2.2);
startB = (float) Math.pow(startB, 2.2);
endR = (float) Math.pow(endR, 2.2);
endG = (float) Math.pow(endG, 2.2);
endB = (float) Math.pow(endB, 2.2);
/*
*根据动画时间因子,计算出中间的过渡颜色
*/
// compute the interpolated color in linear space
float a = startA + fraction * (endA - startA);
float r = startR + fraction * (endR - startR);
float g = startG + fraction * (endG - startG);
float b = startB + fraction * (endB - startB);
// convert back to sRGB in the [0..255] range
a = a * 255.0f;
r = (float) Math.pow(r, 1.0 / 2.2) * 255.0f;
g = (float) Math.pow(g, 1.0 / 2.2) * 255.0f;
b = (float) Math.pow(b, 1.0 / 2.2) * 255.0f;
/*
*重新将分离的颜色通道组合返回过渡颜色
*/
return Math.round(a) << 24 | Math.round(r) << 16 | Math.round(g) << 8 | Math.round(b);
}