Android:自定义圆角图片

自定义圆角图片：代码如下 

public class RoundImageView extends android.support.v7.widget.AppCompatImageView{
 
	public RoundImageView(Context context) {
		super(context);
	}
 
	public RoundImageView(Context context, AttributeSet attrs) {
		super(context, attrs);
 
	}
 
	public RoundImageView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
 
	}
 
	@Override
	protected void onDraw(Canvas canvas) {
		// 获取当前控件的 drawable
		Drawable drawable = getDrawable();
		if (drawable == null) {
			return;
		}
		// 这里 get 回来的宽度和高度是当前控件相对应的宽度和高度（在 ml 设置）
		if (getWidth() == 0 || getHeight() == 0) {
			return;
		}
		// 画笔
		Paint paint = new Paint();
		// 颜色设置
		paint.setColor(0xff424242);
		// 抗锯齿
		paint.setAntiAlias(true);
		// 获取 bitmap，即传入 imageview 的 bitmap
		Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
		// 标志
		int saveFlags = Canvas.MATRIX_SAVE_FLAG | Canvas.CLIP_SAVE_FLAG | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
				| Canvas.FULL_COLOR_LAYER_SAVE_FLAG | Canvas.CLIP_TO_LAYER_SAVE_FLAG;
		canvas.saveLayer(0, 0, getWidth(), getHeight(), null, saveFlags);
		// 画遮罩，画出来就是一个和空间大小相匹配的圆
		float radius = getWidth() / 2 >= getHeight() / 2 ? getHeight() / 2 : getWidth() / 2;
		canvas.drawCircle(getWidth() / 2, getHeight() / 2, radius, paint);
		// Paint 的 Xfermode，PorterDuff.Mode.SRC_IN 取两层图像的交集部门, 只显示上层图像。
		PorterDuffXfermode xfermode = new PorterDuffXfermode(PorterDuff.Mode.SRC_IN);
		paint.setXfermode(xfermode);
		// 空间的大小 /bitmap 的大小 =bitmap 缩放的倍数
		float scaleWidth = ((float) getWidth()) / bitmap.getWidth();
		float scaleHeight = ((float) getHeight()) / bitmap.getHeight();
		System.out.println("getWidth:" + getWidth());
		System.out.println("bitmap.getWidth:" + bitmap.getWidth());
		Matrix matrix = new Matrix();
		matrix.postScale(scaleWidth, scaleHeight);
		// bitmap 缩放
		bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
		// draw 上去
		canvas.drawBitmap(bitmap, 0, 0, paint);
		// paint.setXfermode(null);
		canvas.restore();
	}
}