Android实现自定义ImageView的圆角矩形图片效果

package com.xc.xcskin.view;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.ImageView;
/**
 * 自定义的圆角矩形ImageView，可以直接当组件在布局中使用。
 * @author caizhiming
 *
 */
public class XCRoundRectImageView extends ImageView{
 private Paint paint;
 public XCRoundRectImageView(Context context) { 
 this(context,null); 
 } 
 public XCRoundRectImageView(Context context, AttributeSet attrs) { 
 this(context, attrs,0); 
 } 
 public XCRoundRectImageView(Context context, AttributeSet attrs, int defStyle) { 
 super(context, attrs, defStyle); 
 paint = new Paint();
 } 
 /**
 * 绘制圆角矩形图片
 * @author caizhiming
 */
 @Override 
 protected void onDraw(Canvas canvas) { 
 Drawable drawable = getDrawable(); 
 if (null != drawable) { 
 Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap(); 
 Bitmap b = getRoundBitmap(bitmap, 20); 
 final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight()); 
 final Rect rectDest = new Rect(0,0,getWidth(),getHeight());
 paint.reset(); 
 canvas.drawBitmap(b, rectSrc, rectDest, paint); 
 } else { 
 super.onDraw(canvas); 
 } 
 } 
 /**
 * 获取圆角矩形图片方法
 * @param bitmap
 * @param roundPx,一般设置成14
 * @return Bitmap
 * @author caizhiming
 */
 private Bitmap getRoundBitmap(Bitmap bitmap, int roundPx) { 
 Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), 
 bitmap.getHeight(), Config.ARGB_8888); 
 Canvas canvas = new Canvas(output); 
 final int color = 0xff424242;
 final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight()); 
 final RectF rectF = new RectF(rect);
 paint.setAntiAlias(true); 
 canvas.drawARGB(0, 0, 0, 0); 
 paint.setColor(color); 
 int x = bitmap.getWidth(); 
 canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
 paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN)); 
 canvas.drawBitmap(bitmap, rect, rect, paint); 
 return output; 
 } 
} 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent" > 
 <com.xc.xcskin.view.XCRoundRectImageView
 android:id="@+id/roundRectImageView" 
 android:layout_centerInParent="true" 
 android:layout_width="200dp" 
 android:layout_height="200dp"
 android:src="@drawable/roundimageview"
 /> 
</RelativeLayout>