自定义圆角的ImageView 还可以实现图片的圆形、椭圆形展示。

为了达到美观的效果，项目中的所有图片显示都是圆角显示。然而Android的ImageView没有圆角属性，而让UI把所有图片都处理成圆角，也不合适。这里采用自定义的方法来自定义一个支持圆角的ImageView，然后在布局中引用这个类来布局就可以了。同时，该自定义ImageView还支持绘制圆形和椭圆形的ImageView。可以根据实际需要来选择。 这个代码是网上找的 和大家一起分享下

import android.content.Context;
import android.graphics.*;
import android.graphics.Bitmap.Config;
import android.graphics.PorterDuff.Mode;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.ImageView;

import java.lang.ref.WeakReference;

/**
* 使用Xfermode渲染方案实现圆角矩形、椭圆ImageView
* @author caizhiming
*
*/
public class XCRoundImageViewByXfermode extends ImageView{

//数据定义
private Paint mPaint;
private Xfermode mXfermode = new PorterDuffXfermode(Mode.DST_IN);
private Bitmap mMaskBitmap; //用来做
private int mRoundBorderRadius;//圆角大小
private int mType;//类型：圆形、圆角或椭圆

private WeakReference<Bitmap> mBufferBitmap;//使用缓存技术，避免每次都执行onDraw
public static final int TYPE_CIRCLE = 1;//圆形
public static final int TYPE_ROUND = 2;//圆角矩形
public static final int TYPE_OVAL = 3;//椭圆形
private static final int DEFAULT_ROUND_BORDER_RADIUS = 10;//默认圆角大小

//构造方法
public XCRoundImageViewByXfermode(Context context){
this(context, null);
}
public XCRoundImageViewByXfermode(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub

mPaint = new Paint();
mPaint.setAntiAlias(true);//设置消除锯齿
mType = TYPE_ROUND;
mRoundBorderRadius = DEFAULT_ROUND_BORDER_RADIUS;
}

/**
* 测量view的大小
*/
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// TODO Auto-generated method stub
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
//如果类型是圆形，则强制设置view的宽高一致，取宽高的较小值
if(mType == TYPE_CIRCLE){
int width = Math.min(getMeasuredWidth(),getMeasuredHeight());
setMeasuredDimension(width, width);
}
}
/**
* 绘制view的内容
*/
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
//从缓存中取出bitmap
Bitmap bmp = (mBufferBitmap == null ? null:mBufferBitmap.get());
if(bmp == null || bmp.isRecycled()){
//如果没有缓存存在的情况
//获取drawable
Drawable drawable = getDrawable();
//获取drawable的宽高
int dwidth = drawable.getIntrinsicWidth();
int dheight = drawable.getIntrinsicHeight();
Log.v("czm","dwidth="+dwidth+",width="+getWidth());
if(null != drawable){
bmp = Bitmap.createBitmap(getWidth(), getHeight(),
Config.ARGB_8888);
float scale = 1.0f;
//创建画布
Canvas drawCanvas = new Canvas(bmp);
//按照bitmap的宽高，以及view的宽高，计算缩放比例；因为设置的src宽高
//比例可能和imageview的宽高比例不同，这里我们不希望图片失真；

if(mType == TYPE_CIRCLE)
{//如果是圆形
scale = getWidth() * 1.0F / Math.min(dwidth, dheight);
}else if (mType == TYPE_ROUND || mType == TYPE_OVAL)
{//如果是圆角矩形或椭圆
// 如果图片的宽或者高与view的宽高不匹配，计算出需要缩放的比例；
//缩放后的图片的宽高，一定要大于我们view的宽高；所以我们这里取大值；
scale = Math.max(getWidth() * 1.0f / dwidth, getHeight()
* 1.0f / dheight);
}
Log.v("czm","scale="+scale);
//根据缩放比例，设置bounds，即相当于做缩放图片
drawable.setBounds(0, 0, (int)(scale * dwidth), (int)(scale * dheight));
drawable.draw(drawCanvas);
//获取bitmap，即圆形、圆角或椭圆的bitmap
if(mMaskBitmap == null || mMaskBitmap.isRecycled()){
mMaskBitmap = getDrawBitmap();
}
//为paint设置Xfermode 渲染模式
mPaint.reset();
mPaint.setFilterBitmap(false);
mPaint.setXfermode(mXfermode);
//绘制不同形状
drawCanvas.drawBitmap(mMaskBitmap, 0, 0,mPaint);
mPaint.setXfermode(null);

//将准备好的bitmap绘制出来
canvas.drawBitmap(bmp, 0, 0, null);
//bitmap缓存起来，避免每次调用onDraw，分配内存
mBufferBitmap = new WeakReference<Bitmap>(bmp);
}

}else{
//如果缓存还存在的情况
mPaint.setXfermode(null);
canvas.drawBitmap(bmp, 0.0f, 0.0f, mPaint);
return;
}
}
/**
* 绘制不同的图形Bitmap
*/
private Bitmap getDrawBitmap(){
Bitmap bitmap = Bitmap.createBitmap(getWidth(), getHeight(),
Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.BLACK);

if(mType == TYPE_CIRCLE)
{//绘制圆形
canvas.drawCircle(getWidth() / 2, getWidth() / 2, getWidth() / 2,
paint);
}else if(mType == TYPE_ROUND)
{//绘制圆角矩形
canvas.drawRoundRect(new RectF(0, 0, getWidth(), getHeight()),
mRoundBorderRadius, mRoundBorderRadius, paint);
}else if(mType == TYPE_OVAL ){
//绘制椭圆
canvas.drawOval(new RectF(0, 0, getWidth(), getHeight()), mPaint);
}

return bitmap;
}
/**
* 因为使用了缓存技术，所以需要在invalidate中做些回收释放资源的处理
*/
@Override
public void invalidate() {
// TODO Auto-generated method stub
mBufferBitmap = null;
if(mMaskBitmap != null){
mMaskBitmap.recycle();
mMaskBitmap = null;
}
super.invalidate();
}

public int getRoundBorderRadius() {
return mRoundBorderRadius;
}
public void setRoundBorderRadius(int mRoundBorderRadius) {
if(this.mRoundBorderRadius != mRoundBorderRadius){
this.mRoundBorderRadius = mRoundBorderRadius;
invalidate();
}
}
public int getType() {
return this.mType;
}
public void setType(int mType) {
if(this.mType != mType){
this.mType = mType;
invalidate();
}
}
}

效果如图