有没有更好的方法将数据传递给没有有状态、继承的小部件的子级?

Question

我有一个像下面的类，

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，我从虚线将相同的三个参数传递给_DottedLinePainter现在如果我想为类_DottedLinePainter添加一个新参数，我也必须为虚线创建它......

那么如何在一个地方只定义参数名称呢？但是我不想扩展继承的小部件，因为如果我这样做，那么它就预示着我更改虚线状态小部件，这是不必要的。

Answer 1

您可以通过直接将小部件传递给自定义绘制器来减少重复，而不是传递小部件的属性：

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){
...
}
...
}