public void draw(@NonNull Canvas canvas) { //將繪制操作保存到新的圖層，因為圖像合成是很昂貴的操作，將用到硬件加速，這里將圖像合成的處理放到離屏緩存中進行 int saveCount = canvas.saveLayer(0, 0, canvas.getWidth(), canvas.getHeight(), srcPaint, Canvas.ALL_SAVE_FLAG); //dst 繪制目標圖層 innerDrawable.draw(canvas); //設置混合模式 srcPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR)); //src 繪制源圖 canvas.drawPath(srcPath, srcPaint); //清除混合模式 srcPaint.setXfermode(null); //還原畫布 canvas.restoreToCount(saveCount);}

setLayerType(View.LAYER_TYPE_SOFTWARE, null);

<FrameLayout android:layout_width="match_parent" android:layout_height="match_parent"> <ImageView  android:layout_width="match_parent"  android:layout_height="match_parent"  android:background="@drawable/crop_image_bg" /> <com.jian.cropimage.CoverView  android:layout_width="match_parent"  android:layout_height="match_parent"  android:background="@color/crop_image_cover_view_bg">  <!-- 根據(jù)這個子View所在的位置，計算出透明矩形的位置，開發(fā)時的所見即所得 -->  <ImageView   android:id="@+id/crop_image_cover_view_hole"   android:layout_width="250dp"   android:layout_height="250dp"   android:layout_gravity="center" /> </com.jian.cropimage.CoverView></FrameLayout>

import android.graphics.Canvas;import android.graphics.ColorFilter;import android.graphics.Paint;import android.graphics.Path;import android.graphics.PorterDuff;import android.graphics.PorterDuffXfermode;import android.support.annotation.NonNull;import android.support.annotation.Nullable;/** * 說明：支持中間出現(xiàn)透明區(qū)域的drawable <br/> * 通過{@link #setSrcPath(Path)}設定透明區(qū)域的形狀 <br/> * 作者：楊健 * 時間：2017/9/4. */public class HoleDrawable extends Drawable { private Paint srcPaint; private Path srcPath = new Path(); private Drawable innerDrawable; public HoleDrawable(Drawable innerDrawable) {  this.innerDrawable = innerDrawable;  srcPath.addRect(100, 100, 200, 200, Path.Direction.CW);  srcPaint = new Paint(Paint.ANTI_ALIAS_FLAG);  srcPaint.setColor(0xffffffff); } /**  * 設置內(nèi)部透明的部分  *  * @param srcPath  */ public void setSrcPath(Path srcPath) {  this.srcPath = srcPath; } @Override public void draw(@NonNull Canvas canvas) {  innerDrawable.setBounds(getBounds());  if (srcPath == null || srcPath.isEmpty()) {   innerDrawable.draw(canvas);  } else {   //將繪制操作保存到新的圖層，因為圖像合成是很昂貴的操作，將用到硬件加速，這里將圖像合成的處理放到離屏緩存中進行   int saveCount = canvas.saveLayer(0, 0, canvas.getWidth(), canvas.getHeight(), srcPaint, Canvas.ALL_SAVE_FLAG);   //dst 繪制目標圖   innerDrawable.draw(canvas);   //設置混合模式   srcPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));   //src 繪制源圖   canvas.drawPath(srcPath, srcPaint);   //清除混合模式   srcPaint.setXfermode(null);   //還原畫布   canvas.restoreToCount(saveCount);  } } @Override public void setAlpha(int alpha) {  innerDrawable.setAlpha(alpha); } @Override public void setColorFilter(@Nullable ColorFilter colorFilter) {  innerDrawable.setColorFilter(colorFilter); } @Override public int getOpacity() {  return innerDrawable.getOpacity(); }}

import android.content.Context;import android.graphics.Path;import android.graphics.drawable.HoleDrawable;import android.support.annotation.NonNull;import android.support.annotation.Nullable;import android.util.AttributeSet;import android.view.View;import android.widget.FrameLayout;/** * 能夠局部透明的layout，也就是將background處理成帶洞洞的效果 <br/> * 當然了，形狀要你自己指定，目前想不到好的思路自動處理各種形狀，有的話就直接完善了 <br/> * 根據(jù)個crop_image_cover_view_hole子View的位置，確定透明區(qū)域 <br/> * 作者：楊健 * 時間：2017/9/4. */public class HoleBackgroundLayout extends FrameLayout { private HoleDrawable background; public HoleBackgroundLayout(@NonNull Context context) {  super(context);  initView(context, null, 0); } public HoleBackgroundLayout(@NonNull Context context, @Nullable AttributeSet attrs) {  super(context, attrs);  initView(context, attrs, 0); } public HoleBackgroundLayout(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {  super(context, attrs, defStyleAttr);  initView(context, attrs, defStyleAttr); } private void initView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {  background = new HoleDrawable(getBackground());  setBackground(background); } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) {  super.onLayout(changed, left, top, right, bottom);  resetBackgroundHoleArea(); } private void resetBackgroundHoleArea() {  Path path = null;  // 以crop_image_cover_view_hole子View為范圍構造需要透明顯示的區(qū)域  View v0 = findViewById(R.id.crop_image_cover_view_hole);  if (v0 != null) {   path = new Path();   // 矩形透明區(qū)域   path.addRect(v0.getLeft(), v0.getTop(), v0.getRight(), v0.getBottom(), Path.Direction.CW);  }  if (path != null) {   background.setSrcPath(path);  } }}