Android仿QQ圆形头像

先上效果图：

实现思路：

        自定义一个View，继承ImageView，通过PorterDuffXfermode实现一个Mask效果，并在onDraw中画出来。

自定义View的代码：

public class CircleClipView extends ImageView{
	
    private Paint backgroundPaint = null;
    private Paint maskPaint = null;
    
    private int backgroundColor = -1;
    
	public CircleClipView(Context context) {
		// TODO Auto-generated constructor stub
		super(context);
		init();
	}
	
	public CircleClipView(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
		TypedArray a = context.obtainStyledAttributes(attrs,R.styleable.circleview);
		backgroundColor = a.getColor(R.styleable.circleview_backgroundcolor, Color.WHITE);
		a.recycle();
		init();
	}
	
	private void init(){
		maskPaint = new Paint();
		PorterDuffXfermode porterDuffXfermode = new PorterDuffXfermode(PorterDuff.Mode.SRC_IN);
		maskPaint.setXfermode(porterDuffXfermode);
		maskPaint.setColor(Color.TRANSPARENT);
		maskPaint.setAntiAlias(true);
		
		backgroundPaint = new Paint();
		backgroundPaint.setColor(backgroundColor);
		backgroundPaint.setAntiAlias(true);  
		
	}
	
	private Bitmap getMask(){
		Bitmap b = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);  
		Canvas canvas = new Canvas(b);
		RectF rectF = new RectF(0, 0, getWidth(), getHeight());
		canvas.drawRect(rectF, backgroundPaint);
		canvas.drawOval(rectF, maskPaint);
		return b;
	}
	
	private Bitmap scaleDrawable(Drawable drawable){
		Bitmap b = ((BitmapDrawable) drawable).getBitmap();
		Matrix matrix = new Matrix();
		float scaleWidth = ((float) getWidth()) / b.getWidth();    
        float scaleHeight = ((float) getHeight()) / b.getHeight();   
		matrix.postScale(scaleWidth, scaleHeight);
		Bitmap bitmap = Bitmap.createBitmap(b, 0, 0, b.getWidth(), b.getHeight(),matrix, true);
		return bitmap;
	}
	
	@Override
	protected void onDraw(Canvas canvas)
	{
		Bitmap sourceBitmap = scaleDrawable(getDrawable());
		if(sourceBitmap != null) canvas.drawBitmap(sourceBitmap, 0, 0, null);
		canvas.drawBitmap(getMask(), 0, 0, null);
	}
}

XML代码