Flutter 如何在flatter中向该类添加参数？

这是我要添加参数的类。例如，调用MyProgressLine（）时，我希望传递一个整数并在Offset方法中使用它

class MyProgressLine extends CustomPainter {
  MyProgressLine();

  @override
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint()
      ..color = Colors.green
      ..strokeWidth = 3.0
      ..style = PaintingStyle.stroke;

    double endPointsRadius = 5.0;

    // Draws starting point
    canvas.drawCircle(Offset.zero, endPointsRadius, paint);
    canvas.drawLine(
        Offset(endPointsRadius, 0.0), Offset(endPointsRadius + 25, 0.0), paint);

    // Draws current progress line
    paint.style = PaintingStyle.fill;
    canvas.drawCircle(Offset(endPointsRadius + 25, 0.0), 3.0, paint);

    // Draws endpoint
    paint.style = PaintingStyle.stroke;
    paint.color = Colors.grey.withOpacity(0.5);
    canvas.drawLine(Offset(endPointsRadius + 25, 0.0), Offset(100, 0.0), paint);
    canvas.drawCircle(
        Offset(100 + endPointsRadius, 0.0), endPointsRadius, paint);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => false;
}

---

更改构造函数：

MyProgressLine({int offsetBy = 0});

然后在需要时使用

offsetBy

class MyProgressLine extends CustomPainter {
  final int myParam;
  MyProgressLine(this.myParam);

  @override
  void paint(Canvas canvas, Size size) {
      // ... 
      // Draws starting point
      canvas.drawCircle(Offset.zero, endPointsRadius, paint);
      canvas.drawLine(
          Offset(endPointsRadius, 0.0), Offset(endPointsRadius + 25 + myParam, 0.0), paint);

      // ...

    }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => false;
}

无论何时使用

MyProgressLine

，都可以这样称呼它：

MyProgressLine（x）其中x是所需的任意整数