扩展ImageView类，将图片加上边框，并且设置边框颜色

public class ImageViewExt extends ImageView {
    //将图片加灰色的边框
    private int color;

    public ImageViewExt(Context context) {
        super(context);
        color=Color.WHITE;
  }

   public ImageViewExt(Context context, AttributeSet attrs) {
         super(context, attrs);
         color=Color.WHITE;
   }


    @Override
     protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //画边框
        Rect rec=canvas.getClipBounds();
        rec.bottom--;
        rec.right--;
        Paint paint=new Paint();
        paint.setColor(color);//设置颜色
        paint.setStrokeWidth(10);//设置画笔的宽度
        paint.setStyle(Paint.Style.STROKE);//设置画笔的风格-不能设成填充FILL否则看不到图片了
        canvas.drawRect(rec, paint);
    }
}