Flutter 如何扩展BorderSide以生成渐变边框

我试图通过扩展“border Side”类向border添加渐变，如下所示：

class GradientBorderSide extends BorderSide {
  const GradientBorderSide(
      {this.color = const Color(0x00000000),
      this.width = 1.0,
      this.style = BorderStyle.solid,
      this.gradient =
          const LinearGradient(colors: [Colors.black, Colors.white])})
      : super(color: color, width: width, style: style);

  final Gradient gradient;
  final Color color;
  final double width;
  final BorderStyle style;

  @override
  Paint toPaint() {
    switch (style) {
      case BorderStyle.solid:
        return Paint()
          ..strokeWidth = width
          ..style = PaintingStyle.stroke
          ..shader = gradient.createShader(Rect.fromCenter(
              center: Offset.zero, width: width, height: width));
      case BorderStyle.none:
        return Paint()
          ..color = const Color(0x00000000)
          ..strokeWidth = 0.0
          ..style = PaintingStyle.stroke;
    }
    return null;
  }
}

然后将其应用于按钮：

SizedBox(
                  width: 75,
                  height: 75,
                  child: RaisedButton(
                    onPressed: () {},
                    shape: CircleBorder(
                      //borderRadius: BorderRadius.circular(5),
                      side: GradientBorderSide(
                          width: 10,
                          gradient: LinearGradient(
                            begin: Alignment.topLeft,
                            end: Alignment(0.5, .05),
                            colors: [Colors.red, Colors.orange],
                            tileMode: TileMode.repeated,
                          )),
                    ),
                  ),
                )

---

渐变看起来不错，但当按下按钮时，渐变消失，边框颜色显示是否有颜色，然后渐变重新出现。

如果您想给边框添加渐变，则可以实现相同的效果，然后只需将两个容器堆叠在一起，一个容器应该比第二个容器大一点，然后将渐变应用到底部的容器底部的容器将作为边界。好主意，非常感谢。但我需要它更通用，通过扩展border端，它可以应用于任何接受border的小部件。