Android在ImageView中绘制边框

Question

我想在图像周围画一个边框。但是我无法在 ImageView 本身对齐边框(就像它大部分完成的那样)，因为我使用 ImageMatrix 平移和缩放 ImageView 内部的图像(ImageView 本身是 fill_parent/填充整个屏幕)。我有想法添加第二个图像(看起来像边框)并以与应该有边框的图像相同的方式转换和缩放它，但这样做不是很方便。有没有人有更好的想法来实现该目标？

Answer 1

有两种方法可以实现:1) 向 imageView 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) 另一种选择是重写 View 的绘制方法并在那里绘制边框:

@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，您要给出要绘制的线的中间部分(!)而且我还没有运行，也没有编译它，所以我不能 100% 确定它是正确的，但这些是方法: ) 矩形边界应该是您 View 的边界矩形 - (0,0,width,height)。