PorterDuffColorFilter在项目中的基本使用

   private void setUI(float fraction){
        //背景只需要设置透明度，255是全不透明
        headBg.setAlpha((int) (fraction*255)); //这个headBg是标题栏

        //This evaluator can be used to perform type interpolation between integer values that represent ARGB colors.
        //这个求值器用来执行计算用整形表示的颜色的差值
        ArgbEvaluator argbEvaluator = new ArgbEvaluator();
        int   startColor = ActivityCompat.getColor(MainActivity.this,R.color.colorPrimary);
        int   endColor   = Color.WHITE;

        //根据fraction计算出开始和结束中间的色值
        int calcColor = (int) argbEvaluator.evaluate(fraction, startColor, endColor);

        ColorFilter colorFilter = new PorterDuffColorFilter(calcColor, PorterDuff.Mode.SRC_IN);


        //应用颜色过滤器
        iv1Drawable.setColorFilter(colorFilter);
        iv2Drawable.setColorFilter(colorFilter);
    }