我用画矩形填充之外的矩形。我尝试了一些这一点。但不能得到完美的一个我所期待的。

I am drawing an Rectangle with outside of rectangle fill. I tried some of this. But cant get the perfect one what i expected.

这是我所期待的。

我试过

    Point pTopLeft = new Point();
    Point pBotRight = new Point();
    pTopLeft.x = 100;
    pTopLeft.y = 100;
    pBotRight.x = canvas.getWidth() - 100;
    pBotRight.y = canvas.getHeight() - 100;
    Rect above = new Rect(0, 0, canvas.getWidth(), pTopLeft.y);
    paint.setColor(Color.parseColor("#77000000"));
    canvas.drawRect(above, paint);
    Rect left = new Rect(0, pTopLeft.y, pTopLeft.x, pBotRight.y);
    paint.setColor(Color.parseColor("#77000000"));

    canvas.drawRect(left, paint);
    Rect right = new Rect(pBotRight.x, pTopLeft.y, canvas.getWidth(),
            pBotRight.y);
    paint.setColor(Color.parseColor("#77000000"));
    canvas.drawRect(right, paint);
    Rect bottom = new Rect(0, pBotRight.y, canvas.getWidth(),
            canvas.getHeight());

    paint.setColor(Color.parseColor("#77000000"));
    Paint paint_text = new Paint();
    paint_text.setColor(Color.WHITE);
    paint_text.setTextSize(50);
    paint_text.setTextAlign(Align.CENTER);

    canvas.drawText("Position Card in this Frame", canvas.getWidth() / 2,
            canvas.getHeight() - 30, paint_text);
    canvas.drawRect(bottom, paint);

和得到这样

但我想绘制矩形并填充边界之外实现了圆角的边框。我该怎么办呢？

But i want to draw the rectangle and fill outside the bounds to achieve the rounded border. How can i do it?

修改当我试图画出了一个矩形之一。布局是这样的..

EDIT When i tries to draw the rectangle one over one. The layout is like this..

这是我不能给 Col​​or.TRANSPARENT 为中心的矩形充分tranparents第二个矩形。

That i cant give Color.TRANSPARENT for the center rectangle which fully tranparents the second rectangle..

推荐答案

我还不能完全确定你要完成的任务。告诉你的形状可以得出如下：

I'm still not entirely sure what you're trying to accomplish. The shape you show can be drawn as follows:

// set up some constants
int w = canvas.getWidth();
int h = canvas.getHeight();
RectF rect = new RectF(100, 100, w - 100, h - 100);
float radius = 10.0f; // should be retrieved from resources and defined as dp
float borderWidth = 2.0f; // ditto
int innerRectFillColor = 0x33000000; // or whatever shade it should be

// first fill the interior
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(innerRectFillColor);
paint.setStyle(Paint.Style.FILL);
canvas.drawRoundRect(rect, radius, radius, paint);
// then draw the border
paint.setColor(Color.WHITE);
paint.setStrokeWidth(borderWidth);
paint.setStyle(Paint.Style.STROKE);
canvas.drawRoundRect(rect, radius, radius, paint);

如果不是你想画围绕孔（所以背景显示通过），绘制矩形周围不会因圆角的工作诀窍（边框也使得它更复杂）。相反，你可以创建一个单独的位图，有一个透明的孔，然后得出。你需要使用的波特 - 达夫传输模式清除冲位图中的孔：

If instead you want to draw around a hole (so the background shows through), the trick of drawing the surrounding rectangles won't work because of the rounded corners (the border also makes it more complicated). Instead, you can create a separate Bitmap that has a transparent hole and then draw that. You'll need to use a Porter-Duff transfer mode of CLEAR to punch the hole in the bitmap:

// same constants as above except innerREctFillColor is not used. Instead:
int outerFillColor = 0x77000000;

// first create an off-screen bitmap and its canvas
Bitmap bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
Canvas auxCanvas = new Canvas(bitmap);

// then fill the bitmap with the desired outside color
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(outerFillColor);
paint.setStyle(Paint.Style.FILL);
auxCanvas.drawPaint(paint);

// then punch a transparent hole in the shape of the rect
paint.setXferMode(new PorterDuffXferMode(PorterDuff.Mode.CLEAR));
auxCanvas.drawRoundRect(rect, radius, radius, paint);

// then draw the white rect border (being sure to get rid of the xfer mode!)
paint.setXferMode(null);
paint.setColor(Color.WHITE);
paint.setStyle(Paint.Style.STROKE);
auxCanvas.drawRoundRect(rect, radius, radius, paint);

// finally, draw the whole thing to the original canvas
canvas.drawBitmap(bitmap, 0, 0, paint);