Android利用贝塞尔曲线绘制动画的示例代码

class AnimationBezierPainter extends CustomPainter {
  AnimationBezierPainter({required this.animationValue});
  final double animationValue;
  @override
  void paint(canvas canvas, Size size) {
    final lineWidth = 6.0;
    paint.strokeWidth = lineWidth;
    paint.style = PaintingStyle.stroke;
    final colors = [
      Color(0xFFE05100),
      Color(0xFFF0A060),
      Color(0xFFE0E000),
      Color(0xFF10F020),
      Color(0xFF2080F5),
      Color(0xFF104FF0),
      Color(0xFFA040E5),
    ];

    final lineNumber = 7;
    for (var i = 0; i < lineNumber; ++i) {
      paint.color = colors[i % colors.length];
      _drawAnimatedLines(canvas, paint, size, size.height / 4 + i * lineWidth);
    }
  }

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

  _drawRainbowLines(Canvas canvas, Paint paint, Size size, yPos) {
    var yGap = 60.0;
    var p0 = Offset(0, yPos - yGap / 2);
    var p1 = Offset(size.width * 2 / 3, yPos - yGap);
    var p2 = Offset(size.width / 3, yPos + yGap);
    var p3 = Offset(size.width, yPos + yGap * 1.5);
    var path = Path();
    path.moveTo(p0.dx, p0.dy);
    for (var t = 1; t <= (100 * animationValue).toInt(); t += 1) {
      var curvePoint =
          BezierUtil.get3OrderBezierPoint(p0, p1, p2, p3, t / 100.0);

      path.lineTo(curvePoint.dx, curvePoint.dy);
    }
    canvas.drawPath(path, paint);
  }
}

@override
void paint(Canvas canvas, Size size) {
  var paint = Paint()..color = Colors.black54;
  final lineWidth = 2.0;
  paint.strokeWidth = lineWidth;
  paint.style = PaintingStyle.stroke;

  final lineNumber = 20;
  // 弹簧效果
  final yGap = 2.0 + 16.0 * animationValue;
  for (var i = 0; i < (lineNumber * animationValue).toInt(); ++i) {
    _drawSpiralLines(
        canvas, paint, size, size.width / 2, size.height - i * yGap, yGap);
  }
}

_drawSpiralLines(Canvas canvas, Paint paint, Size size, double xPos,
    double yPos, double yGap) {
  final xWidth = 160.0;
  var p0 = Offset(xPos, yPos);
  var p1 = Offset(xPos + xWidth / 2 + xWidth / 4, yPos - yGap);
  var p2 = Offset(xPos + xWidth / 2 - xWidth / 4, yPos - 3 * yGap);
  var p3 = Offset(xPos, yPos - yGap);
  var path = Path();
  path.moveTo(p0.dx, p0.dy);
  for (var t = 1; t <= 100; t += 1) {
    var curvePoint =
        BezierUtil.get3OrderBezierPoint(p0, p1, p2, p3, t / 100.0);

    path.lineTo(curvePoint.dx, curvePoint.dy);
  }
  canvas.drawPath(path, paint);
}