绘制矩形并填充外部边界

我正在绘制一个矩形，并在矩形外部填充。我尝试了其中一些。但无法得到我所期望的完美的。

这正是我所期望的。

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);

并得到这样的

但我想绘制矩形并填充边界之外以实现圆角边框。我该怎么做？

EDIT当我尝试一对一绘制矩形时。布局是这样的..

我不能给予Color.TRANSPARENT对于完全透明第二个矩形的中心矩形..

我仍然不完全确定你想要完成什么。您显示的形状可以绘制如下：

// 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);

相反，如果您想在孔周围绘制（以便背景显示出来），则绘制周围矩形的技巧将不起作用，因为圆角（边框也使其变得更加复杂）。相反，您可以创建一个单独的Bitmap有一个透明的孔，然后绘制它。您需要使用 Porter-Duff 传输模式CLEAR在位图中打孔：

// 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);