使用颤动绘制时的性能问题 [英] performance issue in drawing using flutter

问题描述

我正在使用gestuereDetector检测偏移量，并使用CustomePaint绘制颤动中的偏移量.但是绘制后，绘制的性能会变慢，因此请帮助我解决此问题.

I'm using gestuereDetector to detect offset and CustomePaint to paint the offset in flutter. but after drawing the performance of drawing is becoming slow so please help me to solve this issue.

如何提高效率.我的代码如下所示

How can I make it more efficient. My code just follows the below

 Widget build(BuildContext context) {
    _currentPainter = new DrawPainting(_points);

    return new Container(
      child: new ConstrainedBox(
        constraints: const BoxConstraints.expand(),
        child: new GestureDetector(
          onPanUpdate: (DragUpdateDetails details) {
            setState(() {
              RenderBox referenceBox = context.findRenderObject();

              Offset localPosition =
              referenceBox.globalToLocal(details.globalPosition);
              _points = new List.from(_points)..add(localPosition);
            });
          },
          onPanEnd: (DragEndDetails details) =>_points.add(null),
          child: new CustomPaint(
            painter: _currentPainter,

          ),
        ),
      ),
    );
  }


class DrawPainting extends CustomPainter {
  List<Offset> points = [];
  Canvas _lastCanvas;
  Size _lastSize;
  DrawPainting(points){

    this.points = points;
  }

  void paint(Canvas canvas, Size size) {
    print({"the main paint is called .... ": {"size" : size}});
    _lastCanvas = canvas;
    _lastSize = size;
    Paint paint = new Paint()
      ..color = Colors.black
      ..strokeCap = StrokeCap.round
      ..strokeWidth = 8.0;


    for (int i = 0; i < points.length - 1; i++) {
      if (points[i] != null &&
          points[i + 1] != null &&
          (points[i].dx >= 0 &&
              points[i].dy >= 0 &&
              points[i].dx < size.width &&
              points[i].dy < size.height) &&
          (points[i + 1].dx >= 0 &&
              points[i + 1].dy >= 0 &&
              points[i + 1].dx < size.width &&
              points[i + 1].dy < size.height)){
        canvas.drawLine(points[i], points[i + 1], paint);
      }
    }
  }
  bool shouldRepaint(DrawPainting other) => other.points != points;
}

推荐答案

通过使用 drawPath ()而不是使用 setState ，可以解决使用Flutter的绘图应用程序中的性能问题. >对于每个要更新的点，请使用 NotifyListener ()进行刷新，这将比setState效率更高.

The performance issue in drawing app using flutter is resolved by using drawPath() and instead of using setState for each points to update use NotifyListener() to refresh than it will be more efficient than setState.

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