flutter - 有没有更好的方法来将数据传递给没有状态的，继承的小部件的子级？

Question

我上了一个类似于的类(class)

class DottedLine extends StatelessWidget{
  final double circleSize, space;
  final Color color;

  DottedLine({@required this.color, this.circleSize = 1.0, this.space = 5.0});

  @override
  Widget build(BuildContext context){
    return CustomPaint(painter: _DottedLinePainter(color: color, circleSize: circleSize, space: space),);
  }

}

另一个类是

class _DottedLinePainter extends CustomPainter{

  _DottedLinePainter({this.color, this.circleSize, this.space});

  final double circleSize, space;
  final Color color;

  @override
  void paint(Canvas canvas, Size size){
  ...
  }
  ...
}

在这里，我从 DottedLine 传递相同的三个参数到 _DottedLinePainter 。现在，如果我想为类 _DottedLinePainter 添加新参数，我也要为 DottedLine创建它。

那么如何只在一个地方定义参数名称呢？但是我不想扩展继承的窗口小部件，如果这样做的话，那么它将强制我更改不必要的 DottedLine StatefulWidget。

Answer 1

您可以通过将窗口小部件直接传递给自定义绘画工具，而不是传递窗口小部件的属性来减少重复:

class DottedLine extends StatelessWidget{
  final double circleSize, space;
  final Color color;

  DottedLine({@required this.color, this.circleSize = 1.0, this.space = 5.0});

  @override
  Widget build(BuildContext context){
    return CustomPaint(painter: _DottedLinePainter(this),);
  }
}

class _DottedLinePainter extends CustomPainter{

  _DottedLinePainter(this.data);

  final DottedLine data;

  @override
  void paint(Canvas canvas, Size size){
  ...
  }
  ...
}