Android -- 自定义ImageView(圆形头像)

package com.chaowen.yixin;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
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;

public class RoundedImageView extends ImageView {

	public RoundedImageView(Context context) {
		super(context);
		// TODO Auto-generated constructor stub
	}

	public RoundedImageView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public RoundedImageView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
	}

	@Override
	protected void onDraw(Canvas canvas) {

		Drawable drawable = getDrawable();

		if (drawable == null) {
			return;
		}

		if (getWidth() == 0 || getHeight() == 0) {
			return; 
		}
		Bitmap b =  ((BitmapDrawable)drawable).getBitmap() ;
		Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);

		int w = getWidth(), h = getHeight();


		Bitmap roundBitmap =  getCroppedBitmap(bitmap, w);
		canvas.drawBitmap(roundBitmap, 0,0, null);

	}

	public static Bitmap getCroppedBitmap(Bitmap bmp, int radius) {
		Bitmap sbmp;
		if(bmp.getWidth() != radius || bmp.getHeight() != radius)
			sbmp = Bitmap.createScaledBitmap(bmp, radius, radius, false);
		else
			sbmp = bmp;
		Bitmap output = Bitmap.createBitmap(sbmp.getWidth(),
				sbmp.getHeight(), Config.ARGB_8888);
		Canvas canvas = new Canvas(output);

		final int color = 0xffa19774;
		final Paint paint = new Paint();
		final Rect rect = new Rect(0, 0, sbmp.getWidth(), sbmp.getHeight());

		paint.setAntiAlias(true);
		paint.setFilterBitmap(true);
		paint.setDither(true);
		canvas.drawARGB(0, 0, 0, 0);
		paint.setColor(Color.parseColor("#BAB399"));
		canvas.drawCircle(sbmp.getWidth() / 2+0.7f, sbmp.getHeight() / 2+0.7f,
				sbmp.getWidth() / 2+0.1f, paint);
		paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
		canvas.drawBitmap(sbmp, rect, rect, paint);


		return output;
	}

}

<com.chaowen.yixin.RoundedImageView
            android:id="@+id/headImageView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginTop="25.0dip"
            android:adjustViewBounds="true"
            android:maxHeight="80dip"
            android:maxWidth="80dip"
            android:src="@drawable/head_default_yixin" />