一键实现app全局黑白方法总结

方法一： 自定义view，设置饱和度为0,变成灰度

原理： 自定义view时，对paint设置setColorFilter，将饱和度设置为0，canvas通过saveLayer把paint替换即可，全局设置时，可以采用以下方式。

创建GrayFrameLayout

public class GrayFrameLayout extends FrameLayout {
     
    private Paint mPaint = new Paint();

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

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

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


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

}

在baseActivity中替换掉默认的fragmentLayout

  @Override
    public View onCreateView(String name, Context context, AttributeSet attrs) {
     
        if("FrameLayout".equals(name)){
     
            int count = attrs.getAttributeCount();
            for (int i = 0; i < count; i++) {
     
                String attributeName = attrs.getAttributeName(i);
                String attributeValue = attrs.getAttributeValue(i);
                if (attributeName.equals("id")) {
     
                    int id = Integer.parseInt(attributeValue.substring(1));
                    String idVal = getResources().getResourceName(id);
                    if ("android:id/content".equals(idVal)) {
     
                        GrayFrameLayout grayFrameLayout = new GrayFrameLayout(context, attrs);
                        return grayFrameLayout;
                    }
                }
            }
        }
        return super.onCreateView(name, context, attrs);
    }

方法二：设置为硬件加速，然后替换paint

具体思路如下：

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

在baseActivity的super.onCreate前执行即可

方法三：不是修改饱和度，直接修改ColorMatrix 的矩阵参数来达到颜色修改，可以用于夜间模式等使用

具体思路如下：

Window window = activity.getWindow();
if (window == null) {
     
    return;
}
View view = window.getDecorView();
Paint paint = new Paint();
// 我们把蓝色减弱为原来的0.7
ColorMatrix cm = new ColorMatrix(new float[]{
     
        -1, 0, 0, 0, 255,
        0, -1, 0, 0, 255,
        0, 0, -1, 0, 255,
        0, 0, 0, 1, 0
});
paint.setColorFilter(new ColorMatrixColorFilter(cm));
view.setLayerType(View.LAYER_TYPE_HARDWARE, paint);

但是有一个很明显的问题，因为我们是对Activity的DecorView做了颜色转换，ImageView是它的Child，所以图片也被反色了,可以单独给ImageView设置一个反向的矩阵让图片恢复原来的颜色：

// 遍历查找ImageView，对其设置逆矩阵
int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
     
    final View childView = parent.getChildAt(i);
    if (childView instanceof ViewGroup) {
     
        takeOffColor((ViewGroup) childView);
    } else if (childView instanceof ImageView) {
     
        Paint paint = new Paint();
        ColorMatrix cm = new ColorMatrix(new float[]{
     
                -1, 0, 0, 0, 255,
                0, -1, 0, 0, 255,
                0, 0, -1, 0, 255,
                0, 0, 0, 1, 0
        });
        paint.setColorFilter(new ColorMatrixColorFilter(cm));
        childView.setLayerType(View.LAYER_TYPE_HARDWARE, paint);
    }
}

感谢：以上来源与鸿洋公众号系列文章，进行一个小笔记汇总