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清明节国家哀悼日时各大APP的黑白模式切换，以下介绍两种方案快速设置APP为黑白模式
方案1：
在Activity 中增加如下代码（可以放到项目的BaseActivity中）：
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); setContentView(R.layout.xxx); //主要是如下代码：
View decorView = getWindow().getDecorView(); Paint paint = new Paint();
ColorMatrix cm = new ColorMatrix(); cm.setSaturation(0);
paint.setColorFilter(new ColorMatrixColorFilter(cm));
decorView.setLayerType(View.LAYER_TYPE_HARDWARE,paint); }
方案2：
1、先定义一个GrayFrameLayout布局
import android.content.Context; import android.graphics.Canvas; import
android.graphics.ColorMatrix; import android.graphics.ColorMatrixColorFilter;
import android.graphics.Paint; import android.util.AttributeSet; import
android.widget.FrameLayout; import androidx.annotation.NonNull; import
androidx.annotation.Nullable; public class GrayFrameLayout extends FrameLayout
{ private Paint mPaint =new Paint(); public GrayFrameLayout(@NonNull Context
context) { super(context); } public GrayFrameLayout(@NonNull Context context,
@Nullable AttributeSet attrs) { super(context, attrs); ColorMatrix cm = new
ColorMatrix(); cm.setSaturation(0); mPaint.setColorFilter(new
ColorMatrixColorFilter(cm)); } @Override protected void onDraw(Canvas canvas) {
canvas.saveLayer(null,mPaint,Canvas.ALL_SAVE_FLAG); super.onDraw(canvas); }
@Override protected void dispatchDraw(Canvas canvas) {
canvas.saveLayer(null,mPaint,Canvas.ALL_SAVE_FLAG); super.dispatchDraw(canvas);
} }
2、在Activity（可以放到项目的BaseActivity中）
@Override public View onCreateView(View parent, String name, Context context,
AttributeSet attrs) { if("FrameLayout".equals(name)){ int attributeCount =
attrs.getAttributeCount(); for (int i = 0; i < attributeCount; i++) { String
attributeName = attrs.getAttributeName(i); String attributeValue =
attrs.getAttributeValue(i); if(attributeName.equals("id")){ int id =
Integer.parseInt(attributeValue.substring(1)); String resourceName =
getResources().getResourceName(id);
if("android:id/content".equals(resourceName)){ GrayFrameLayout frameLayout =
new GrayFrameLayout(this,attrs); return frameLayout; } } } } return
super.onCreateView(parent, name, context, attrs); }