Question

我想在画布上画一个圆角矩形填充颜色（或位图）和一个笔划但是没有一些选定的角落而且没有某些选定方面的边界。任何想法我怎么能实现这个目标？

Answer 1

您可以将绘图过程分为两部分。

绘制填充区域

当尝试绘制不受标准sdk API支持的形状时，Canvas.drawPath方法将是一个很好的方法。你可以定义四个变量来表示四个角的半径。

Path path = new Path();
Rect drawingRect = {the rect area you want to draw}
RectF topLeftArcBound = new RectF();
RectF topRightArcBound = new RectF();
RectF bottomLeftArcBound = new RectF();
RectF bottomRightArcBound = new RectF();

topRightArcBound.set(drawingRect.right - topRightRadius * 2, drawingRect.top, drawingRect.right, drawingRect.top + topRightRadius * 2);
bottomRightArcBound.set(drawingRect.right - bottomRightRadius * 2, drawingRect.bottom - bottomRightRadius * 2, drawingRect.right, drawingRect.bottom);
bottomLeftArcBound.set(drawingRect.left, drawingRect.bottom - bottomLeftRadius * 2, drawingRect.left + bottomLeftRadius * 2, drawingRect.bottom);
topLeftArcBound.set(drawingRect.left, drawingRect.top, drawingRect.left + topLeftRadius * 2, drawingRect.top + topLeftRadius * 2);

path.reset();

path.moveTo(drawingRect.left + topLeftRadius, drawingRect.top);

//draw top horizontal line
path.lineTo(drawingRect.right - topRightRadius, drawingRect.top);

//draw top-right corner
path.arcTo(topRightArcBound, -90, 90);

//draw right vertical line
path.lineTo(drawingRect.right, drawingRect.bottom - bottomRightRadius);

//draw bottom-right corner
path.arcTo(bottomRightArcBound, 0, 90);

//draw bottom horizontal line
path.lineTo(drawingRect.left - bottomLeftRadius, drawingRect.bottom);

//draw bottom-left corner
path.arcTo(bottomLeftArcBound, 90, 90);

//draw left vertical line
path.lineTo(drawingRect.left, drawingRect.top + topLeftRadius);

//draw top-left corner
path.arcTo(topLeftArcBound, 180, 90);

path.close();

paint.setStyle(Paint.Style.FILL);
canvas.drawPath(path, paint);

您可以将选定角落的半径设置为零

绘制边框

border包含八个部分：

左上角
第一行
右上角
右线
右下角
底线
左下角
左行

使用int值来包含选中的部分将是一个好主意

private static final int TOP_LEFT_CORNER = 0x1;
private static final int TOP_LINE = 0x2;
private static final int TOP_RIGHT_CORNER = 0x4;
private static final int RIGHT_LINE = 0x8;
private static final int BOTTOM_RIGHT_CORNER = 0x10;
private static final int BOTTOM_LINE = 0x20;
private static final int BOTTOM_LEFT_CORNER = 0x40;
private static final int LEFT_LINE = 0x80;

private int selectedParts = TOP_LEFT_CORNER | TOP_LINE | TOP_RIGHT_CORNER;

现在我们可以根据selectedParts绘制边框：

paint.setStyle(Paint.Style.STROKE);
if((selectedParts & TOP_LINE) > 0){
    canvas.drawLine(drawingRect.left + topLeftRadius, drawingRect.top, drawingRect.right - topRightRadius, drawingRect.top);
}

if((selectedParts & TOP_RIGHT_CORNER) > 0){
    canvas.drawArc(topRightArcBound, -90, 90, false, paint);
}

if((selectedParts & RIGHT_LINE) > 0){
    canvas.drawLine(drawingRect.right, drawingRect.top + topRightRadius, drawingRect.right, drawingRect.bottom - bottomRightRadius, paint);
}

if((selectedParts & BOTTOM_RIGHT_CORNER) > 0){
    canvas.drawArc(bottomRightArcBound, 0, 90, false, paint);
}

if((selectedParts & BOTTOM_LINE) > 0){
    canvas.drawLine(drawingRect.right - bottomRightRadius, drawingRect.bottom. drawingRect.left + bottomLeftRadius, drawingRect.bottom, paint);
}

if((selectedParts & BOTTOM_LEFT_CORNER) > 0){
    canvas.drawArc(bottomLeftArcBound, 90, 90, false, paint);
}

if((selectedParts & LEFT_LINE) > 0){
    canvas.drawLine(drawingRect.left, drawingRect.bottom - bottomLeftRadius, drawingRect.left, drawingRect.top + topLeftRadius, paint);
}

if((selectedParts & TOP_LEFT_CORNER) > 0){
    canvas.drawArc(topLeftArcBound, 180, 90, false, paint);
}

如何在Android画布上绘制局部圆形矩形？

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