dart – 如何在Flutter中绘制自定义圆角矩形边框(ShapeBorder)？

我正在尝试扩展ShapeBorder类以添加一些功能.但只是玩涂料方法,我找到了一些我没想到的东西：

边框的角落和矩形的角落似乎不匹配.我使用了以下代码：

class CustomRoundedRectangleBorder extends ShapeBorder {

  final double borderWidth;
  final BorderRadius borderRadius;

  const CustomRoundedRectangleBorder({
    this.borderWidth: 1.0,this.borderRadius: BorderRadius.zero,})
      : assert(borderRadius != null);

  @override
  EdgeInsetsGeometry get dimensions {
    return new EdgeInsets.all(borderWidth);
  }

  @override
  ShapeBorder scale(double t) {
    return new CustomRoundedRectangleBorder(
      borderWidth: borderWidth * (t),borderRadius: borderRadius * (t),);
  }

  @override
  ShapeBorder lerpFrom(ShapeBorder a,double t) {
    assert(t != null);
    if (a is CustomRoundedRectangleBorder) {
      return new CustomRoundedRectangleBorder(
        borderWidth: ui.lerpDouble(a.borderWidth,borderWidth,t),borderRadius: BorderRadius.lerp(a.borderRadius,borderRadius,);
    }
    return super.lerpFrom(a,t);
  }

  @override
  ShapeBorder lerpTo(ShapeBorder b,double t) {
    assert(t != null);
    if (b is CustomRoundedRectangleBorder) {
      return new CustomRoundedRectangleBorder(
        borderWidth: ui.lerpDouble(borderWidth,b.borderWidth,borderRadius: BorderRadius.lerp(borderRadius,b.borderRadius,);
    }
    return super.lerpTo(b,t);
  }

  @override
  Path getInnerPath(Rect rect,{ TextDirection textDirection }) {
    return new Path()
      ..addRRect(borderRadius.resolve(textDirection).toRRect(rect).deflate(
          borderWidth));
  }

  @override
  Path getOuterPath(Rect rect,{ TextDirection textDirection }) {
    return new Path()
      ..addRRect(borderRadius.resolve(textDirection).toRRect(rect));
  }

  @override
  void paint(Canvas canvas,Rect rect,{ TextDirection textDirection }) {
    rect = rect.deflate(borderWidth / 2.0);

    Paint paint;
    final RRect borderRect = borderRadius.resolve(textDirection).toRRect(rect);
    paint = new Paint()
      ..color = Colors.red
      ..style = PaintingStyle.stroke
      ..strokeWidth = borderWidth;
    canvas.drawRRect(borderRect,paint);
  }
}

并创建矩形如下：

new Container(
              height: 100.0,width: 200.0,padding: new EdgeInsets.all(10.0),decoration: new ShapeDecoration(
                color: Colors.black,shape: new CustomRoundedRectangleBorder(
                  borderRadius: new BorderRadius.all(new Radius.circular(20.0)),borderWidth: 10.0,),// side: new BorderSide(color: Colors.white)
              ),child: new Center(child: new Text("My Button"),

我觉得Flutter源代码采用了类似的方法,但也许我没有看到任何东西.

编辑
将我的绘画风格更改为PaintingStyle.fill,从而在原始矩形而不是边框上绘制一个矩形,我似乎得到了正确的边框：

void paint(Canvas canvas,{ TextDirection textDirection }) {

//    rect = rect.deflate(borderWidth / 2.0);

    Paint paint;
    final RRect borderRect = borderRadius.resolve(textDirection).toRRect(rect);
    paint = new Paint()
      ..color = Colors.red.withOpacity(0.25)
      ..style = PaintingStyle.fill
      ..strokeWidth = borderWidth;
    canvas.drawRRect(borderRect,paint);
  }

我仍然对如何做到这一点感到困惑……

解决方法

你应该使用canvas.drawPath而不是drawRect

Paint paint = new Paint()
  ..color = borderColor
  ..style = PaintingStyle.stroke
  ..strokeWidth = borderWidth;

canvas.drawPath(getOuterPath(rect),paint);

如果你只是想要一个边框,它就足以使用了

@override
  Path getInnerPath(Rect rect,{TextDirection textDirection}) {
    return new Path()
      ..fillType = PathFillType.evenOdd
      ..addPath(getOuterPath(rect),Offset.zero);
  }

dart – 如何在Flutter中绘制自定义圆角矩形边框(ShapeBorder)？

解决方法

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