Question

我想在图像周围画一个边框。但我无法在ImageView本身对齐边框（就像它主要完成一样），因为我使用ImageMatrix翻译和缩放ImageView内部的图像（ImageView本身是fill_parent /填充整个屏幕）。我有想法添加第二张图片（看起来像边框）并翻译＆amp;以与应该有边框的图像相同的方式缩放它，但这样做并不是很方便。有没有人更好地实现这个目标？

Answer 1

有两种方法可以实现这一目标： 1）在imageView中添加填充并为其设置背景颜色。

final ImageView imageView = new ImageView(context);
imageView.setPadding(2*border,2*border,0,0);
final ViewGroup.MarginLayoutParams params = new ViewGroup.MarginLayoutParams(width,height);
params.leftMargin = marginYouWouldSet + border;
params.topMargin = marginYouWouldSet + border;
imageView.setBackgroundDrawable(drawable);
imageView.setBackgroundColor(borderColor);
addView(imageView, params);

2）另一种选择是覆盖视图的绘制方法并绘制边框：

@Override
protected void dispatchDraw(Canvas canvas)
{
 borderDrawable.draw(canvas);
 super.dispatchDraw(canvas);
}
...
public class BorderDrawable extends Drawable{

    private Rect mBounds;
    private Paint mBorderPaint;

    public BorderDrawable(Rect bounds, int thickness, int color) {
        mBounds = bounds;
        mBorderPaint = new Paint();
        mBorderPaint.setStrokeWidth(thickness);
        mBorderPaint.setColor(color);
    }

    @Override
    public void draw(Canvas canvas) {
        //left border
        canvas.drawLine(
                mBounds.left - thickness/2, 
                mBounds.top,
                mBounds.left - thickness/2,
                mBounds.bottom,
                mBorderPaint);
        //top border
        canvas.drawLine(
                mBounds.left, 
                mBounds.top - thickness/2,
                mBounds.right, 
                mBounds.top - thickness/2, 
                mBorderPaint);
        //right border
        canvas.drawLine(
                mBounds.right + thickness/2, 
                mBounds.top,
                mBounds.right + thickness/2,
                mBounds.bottom, 
                mBorderPaint);
        //bottom border
        canvas.drawLine(
                mBounds.left, 
                mBounds.bottom + thickness/2, 
                mBounds.right, 
                mBounds.bottom + thickness/2, 
                mBorderPaint);
    }

}

请注意，你要给你想要绘制的线的中间位置（！）而且我还没有运行，也没有编译它，所以我不是100％确定它是正确的，但这些是方法：）Rect边界应该是视图的边界矩形 - （0,0，宽度，高度）。

Answer 2

或者，将imageView放在某种布局中，然后设置填充：

static class BorderView extends FrameLayout
    {
        public ImageView imageView;

        public BorderView(Context context)
        {
            super(context);

            setLayoutParams(//wrap content)
            imageView = new ImageView(context);//set image and so forth
            addView(imageView);
        }

        public void addSelectionBorder()
        {
            int border = 8;
            setPadding(border,border,border,border);
            setBackgroundColor(Color.BLUE);
        }

        public void removeSelectionBorder()
        {
            int border = 0;
            setPadding(border,border,border,border);
            setBackgroundColor(Color.BLACK);
        }
    }

Android在ImageView中绘制边框

2 个答案: