CircleImageView 用Shader新写的控件，做圆形头像用。

CircleImageView.java

package org.example.ShaderTest;

import android.content.Context;
import android.graphics.*;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.ImageView;

/**
 * Created by jgzhu on 14-1-2.
 */
public class CircleImageView extends ImageView {


    public CircleImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

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

    @Override
    protected void onDraw(Canvas canvas) {

        Drawable drawable = getDrawable();
        int width = getWidth();
        int height = getHeight();

        if (drawable == null) {
            return;
        }
        if (width == 0 || height == 0) {
            return;
        }

        Bitmap b = ((BitmapDrawable) drawable).getBitmap();
        Bitmap bitmap = Bitmap.createBitmap(b, 0, 0, b.getWidth(), b.getHeight(), getImageMatrix(), true);

        BitmapShader shader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        paint.setShader(shader);

        int radius = width < height ? width / 2 : height / 2;

        canvas.drawCircle(width / 2, height / 2, radius, paint);
    }
}