dart - 如何在延迟几秒钟后在 Flutter 的 Canvas 上连续绘画

Question

我定义了一组偏移量。我只想在延迟后在 Canvas 上绘制这些偏移量。这是为了向用户显示绘图的进度。我怎样才能做同样的事情。这是我的代码。但它会在 drawPath 行错误地说“对象已被处置”。

class ReplayPainter extends CustomPainter {
  List<PathData> strokes = new List<PathData>();

  ReplayPainter(this.strokes);

  @override
  void paint(Canvas canvas, Size size) {
    print(strokes.length);
    for (PathData stroke in strokes) {
      Paint strokePaint = new Paint();
      strokePaint.strokeWidth = stroke.strokeWidth;
      strokePaint.style = PaintingStyle.stroke;
      strokePaint.strokeJoin = StrokeJoin.round;
      strokePaint.strokeCap = StrokeCap.round;
      strokePaint.color = stroke.strokeColor;

      Path strokePath = new Path();
      strokePath.addPolygon(stroke.offsets, false);
      Timer _timer = new Timer(const Duration(milliseconds: 100), () {
        canvas.drawPath(strokePath, strokePaint);
      });
    }
  }

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

}

PathData 中有 Offsets。请帮忙。

Answer 1

必须使用AnimationController。阅读以下两部分教程后，我能够做到这一点。

https://medium.com/flutter-io/zero-to-one-with-flutter-43b13fd7b354

https://medium.com/flutter-io/zero-to-one-with-flutter-part-two-5aa2f06655cb