如何在android画布上绘制部分圆形矩形? [英] How to draw a partial round rect on a android canvas?

问题描述

我想在画布上绘制一个圆角矩形填充颜色(或位图)和描边但没有一些选定的角并且没有某些选定边的边框.我有什么想法可以实现这一目标吗?

解决方案

您可以将绘图过程分为两部分.

1. 绘制填充区域

   当尝试绘制标准 sdk API 不支持的形状时，Canvas.drawPath 方法将是一个很好的方法.您可以只定义四个变量来表示四个角的半径.

   Path path = new Path();rectdrawingRect = {你要绘制的矩形区域}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);路径重置()；path.moveTo(drawingRect.left + topLeftRadius,drawingRect.top);//绘制顶部水平线path.lineTo(drawingRect.right - topRightRadius,drawingRect.top);//绘制右上角path.arcTo(topRightArcBound, -90, 90);//画右垂直线path.lineTo(drawingRect.right,drawingRect.bottom - bottomRightRadius);//绘制右下角path.arcTo(bottomRightArcBound, 0, 90);//绘制底部水平线path.lineTo(drawingRect.left - bottomLeftRadius,drawingRect.bottom);//绘制左下角path.arcTo(bottomLeftArcBound, 90, 90);//画左垂直线path.lineTo(drawingRect.left,drawingRect.top + topLeftRadius);//绘制左上角path.arcTo(topLeftArcBound, 180, 90);path.close();Paint.setStyle(Paint.Style.FILL);canvas.drawPath(路径，油漆)；

   并且您可以将选定角的半径设置为零

2. 画边框

   边框包含八个部分:

   • 左上角
   • 顶线
   • 右上角
   • 右侧线
   • 右下角
   • 底线
   • 左下角
   • 左线

   使用 int 值来包含选定的部分将是一个好主意

   <前>私有静态最终 int TOP_LEFT_CORNER = 0x1;私有静态最终 int TOP_LINE = 0x2;私有静态最终 int TOP_RIGHT_CORNER = 0x4;私有静态最终 int RIGHT_LINE = 0x8;私有静态最终 int BOTTOM_RIGHT_CORNER = 0x10;私有静态最终 int BOTTOM_LINE = 0x20;私有静态最终 int BOTTOM_LEFT_CORNER = 0x40;私有静态最终 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:

   <前>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);}

I want to draw on a canvas a round rectangle fill with color (or bitmap) and with a stroke but without some selected corners and also without the border on some selected sides. any ideas how i can achieve this ?

解决方案

you can split the drawing process into two parts.

1. draw the fill area

   when trying to draw a shape that is not support by the standard sdk APIs, Canvas.drawPath method will be a good way to do it.you can just define four variables to represent radiuses of four corners.

   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);
   

   and you can just set radius to zero for selected corners

2. draw border

   border contains eight parts:

   • top-left corner
   • top line
   • top-right corner
   • right line
   • bottom-right corner
   • bottom line
   • bottom-left corner
   • left line

   use a int value to contains selected parts will be a good idea

   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;
   

   and now we can draw border based on selectedParts:

   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);
   }
   

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