Flutter实现支付宝集五福手画福字功能

Listener(
  child: Container(
    alignment: Alignment.center,
    color: Colors.transparent,
    width: double.infinity,
    height: MediaQuery.of(context).size.height,
  ),
  onPointerDown: (PointerDownEvent event) {
    setState(() {
      
    });
  },
  onPointerMove: (PointerMoveEvent event) {
    setState(() {
      
    });
  },
  onPointerUp: (PointerUpEvent event) {
    setState(() {
      
    })；
  },
),

@override
void paint(canvas canvas, Size size) {
  myPaint.strokeCap = StrokeCap.round;
  myPaint.strokeWidth = 15.0;
  if (lines.isEmpty) {
    canvas.drawPoints(PointMode.polyGon, [Offset.zero, Offset.zero], myPaint);
  } else {
    for (int k = 0; k < lines.length; k++) {
      for (int i = 0; i < lines[k].length - 1; i++) {
        if (lines[k][i] != Offset.zero && lines[k][i + 1] != Offset.zero) {
          canvas.drawLine(lines[k][i], lines[k][i + 1], myPaint);
        }
      }
    }
  }
}

/// 所有笔画划线集合
List<List<Offset>> _lines = [];

onPointerDown: (PointerDownEvent event) {
  setState(() {
    _event = event;
    _points.add(_event?.localPosition ?? Offset.zero);
    _lines.add(_points);
  });
},
onPointerMove: (PointerMoveEvent event) {
  setState(() {
    _event = event;
    _points.add(_event?.localPosition ?? Offset.zero);
    _lines.last = _points;
  });
},
onPointerUp: (PointerUpEvent event) {
  setState(() {
    _event = event;
    _points.add(Offset.zero);
    _lines.last = _points;
  });
  _points = [];
},

RenderRepaintBoundary boundary =
    key.currentContext!.findRenderObject() as RenderRepaintBoundary;
var image = await boundary.toImage(pixelRatio: 3.0);
ByteData? byteData = await image.toByteData(fORMat: ImageByteFormat.png);
_postBytes = byteData?.buffer.asUint8List();
var result = await ImageGallerySaver.saveImage(_postBytes!);