Android自定义Drawable实现圆角效果

package com.mydrawable.musk;

import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.Shader;
import android.graphics.drawable.Drawable;

/**
 * Created by musk.
 */

public class CircleDrawable extends Drawable {

 private Paint mPaint;
 private int mWidth;
 private Bitmap mBitmap;

 public CircleDrawable(Bitmap bitmap) {
 mBitmap = bitmap;
 //着色器，设置横向和纵向的着色模式为平铺
 BitmapShader bitmapShader = new BitmapShader(mBitmap,
  Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

 mPaint = new Paint();
 mPaint.setAntiAlias(true);
 mPaint.setDither(true);
 mPaint.setShader(bitmapShader);
 mWidth = Math.min(mBitmap.getWidth(), mBitmap.getHeight());
 }

 //绘制
 @Override
 public void draw(Canvas canvas) {
 canvas.drawCircle(mWidth / 2, mWidth / 2, mWidth / 2, mPaint);
 }

 //设置透明度值
 @Override
 public void setAlpha(int alpha) {
 mPaint.setAlpha(alpha);
 }

 //设置颜色过滤器
 @Override
 public void setColorFilter(ColorFilter colorFilter) {
 mPaint.setColorFilter(colorFilter);
 }

 //返回不透明度
 @Override
 public int getOpacity() {
 return PixelFormat.TRANSLUCENT;
 }

 //返回图片实际的宽高
 @Override
 public int getIntrinsicWidth() {
 return mWidth;
 }

 @Override
 public int getIntrinsicHeight() {
 return mWidth;
 }
}