应用全局灰度显示

https://mp.weixin.qq.com/s/8fTWLYaPhi0to47EUmFd7A

• 给View设置硬件加速或者关闭
  
  view.setLayerType(layerType, null);
  关于ColorMatrix
  https://www.jianshu.com/p/9a44d04f39fc

全局代码

Paint paint = new Paint();
ColorMatrix cm = new ColorMatrix();
cm.setSaturation(0);
mPaint.setColorFilter(new ColorMatrixColorFilter(cm));
getWindow().getDecorView().setLayerType(View.LAYER_TYPE_HARDWARE, paint);

单粒度布局

public class GrayLinearLayout extends LinearLayout {
    private Paint mPaint = new Paint();

    public GrayLinearLayout(Context context, AttributeSet attrs) {
        super(context, attrs);

        ColorMatrix cm = new ColorMatrix();
        cm.setSaturation(0);
        mPaint.setColorFilter(new ColorMatrixColorFilter(cm));
    }

    @Override
    public void draw(Canvas canvas) {
        canvas.saveLayer(null, mPaint, Canvas.ALL_SAVE_FLAG);
        super.draw(canvas);
        canvas.restore();
    }

    @Override
    protected void dispatchDraw(Canvas canvas) {
        canvas.saveLayer(null, mPaint, Canvas.ALL_SAVE_FLAG);
        super.dispatchDraw(canvas);
        canvas.restore();
    }

}