flutter 基础 —— CustomPaint 动画效果

路径动画

示例：

 

 

代码

//路径动画
var path = Path()
  ..moveTo(50, 50)
  ..lineTo(100, 100)
  ..lineTo(200, 90);
var rect1 = Rect.fromCircle(center: Offset(80, 450), radius: 60);
// 中间断开了
path.arcTo(rect1, 0, pi, true);
//由于前面断开了，所以总共有两段路径
ui.PathMetrics pathMetrics = path.computeMetrics();
if (_controller.value < 0.5) {
  var m = pathMetrics.first;
  Path extPath = m.extractPath(0, m.length * _controller.value * 2);
  canvas.drawPath(
      extPath,
      Paint()
        ..strokeWidth = 5
        ..style = PaintingStyle.stroke
        ..color = Colors.red);
} else {
  var m = pathMetrics.last;
  Path extPath = m.extractPath(0, m.length * (_controller.value - 0.5) * 2);
  canvas.drawPath(
      extPath,
      Paint()
        ..strokeWidth = 5
        ..style = PaintingStyle.stroke
        ..color = Colors.red);
}

 

动画串联执行

示例：

 

代码：

    var rect = Rect.fromCircle(center: Offset(200, 200), radius: 50 * _controller.value);
    var path = Path()
      ..moveTo(50, 50)
      ..lineTo(150, 150)
      ..lineTo(150, 300)
      ..lineTo(150, 400)
      ..arcTo(rect, 0, 3.14 * 2, true);

    var paint = Paint()
      ..strokeWidth = 2
      ..color = Colors.green
      ..style = PaintingStyle.stroke;

    var pathMetrics = path.computeMetrics();
    List<PathMetric> metrics = [];
    for (var metric in pathMetrics) {
      metrics.add(metric);
    }
    metrics.asMap().forEach((index, metric) {
      var animate = Tween(begin: 0.0, end: 1.0)
          .animate(CurvedAnimation(parent: _controller,
          curve: Interval(index/metrics.length, 1, curve: Curves.fastOutSlowIn)));
      var path = metric.extractPath(0, metric.length * animate.value);
      canvas.drawPath(path, paint);
    });

 

旋转动画

示例：

 

代码

//旋转动画
canvas.save();
canvas.translate(100, 100);
final radians = _controller.value * 2 * pi;
canvas.rotate(radians);
canvas.translate(-100, -100);
canvas.drawLine(
    Offset(100, 100),
    Offset(130, 196),
    Paint()
      ..strokeWidth = 5
      ..color = Colors.green);
canvas.restore();

 

 

2333