Flutter DoodlePainter canvas画布涂鸦

List<Path> paths = []; //坐标路径
  List<Paint> paints = []; //样式属性

Stack(
        children: [
          //画布底层背景
          Container(
            height: 358,//必须
            padding: const EdgeInsets.fromLTRB(12, 0, 12, 0),
            child: Text("画布底层背景"),
          ),
          //手势
          GestureDetector(
            onPanDown: (details) {
                path = Path();

                //Path 必须单独外部设置，不然不生效
                var paint = Paint();
                paint.color = isColor; //颜色
                paint.style = PaintingStyle.stroke; //笔画模式
                paint.strokeWidth = stroke; //笔画宽度
                paint.blendMode = BlendMode.src; //颜色混合模式

                path.moveTo(details.localPosition.dx, details.localPosition.dy);
                paths.add(path);
                paints.add(paint);
                setState(() {});//通知DOM更新
             
            },
            onPanUpdate: (details) {
                paths.last.lineTo(details.localPosition.dx, details.localPosition.dy);
                setState(() {});//通知DOM更新
              
            },

            //涂鸦
            child: CustomPaint(
              painter: _DoodlePainter(
                paths: paths,
                paints: paints,
              ),
              isComplex: true,
              willChange: true,
              size: Size(double.infinity,356),
            ),
          ),
        ],
      ),

//涂鸦绘制类
class _DoodlePainter extends CustomPainter {
  List<Path> paths;
  List<Paint> paints;

  _DoodlePainter({
    required this.paths,
    required this.paints,
  });

  @override
  void paint(Canvas canvas, Size size) {
    for (var i = 0; i < paths.length; i++) {
      canvas.drawPath(paths[i], paints[i]); // 绘制
    }
  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) {
    return false;
  }
}