听动画来完成 [英] Listen for an animation to complete

问题描述

我想在动画制作完成后执行一个动作。我尝试添加一个statusListener，但这对我不起作用。我的代码如下所示：

I'm trying to perform an action after my animation finishes. I tried adding a statusListener but that is not working for me. My code looks like this:

  @override
  void initState() {
    super.initState();
    _controller = new AnimationController(
      duration: new Duration(milliseconds: 500),
      vsync: this,
    )..addStatusListener((AnimationStatus status) {
      print("Going");
      if (status.index == 3 && spins > 0) { // AnimationStatus index 3 == completed animation
        _controller.duration = new Duration(milliseconds: speed - 50);
        _controller.forward(from: _controller.value == null ? 0.0 : 1 - _controller.value);
        spins--;
        print(speed);
      }
    });
  }

print（Going）; 永远不会执行，但是我的动画确实会结束。怎么了？

The print(Going); never gets executed but my animation does end. What is going wrong?

/// ---编辑--- ///

我正在使用 AnimatedBuilder ，该部分代码如下：

I'm using an AnimatedBuilder, that part of the code looks like this:

child: new AnimatedBuilder(
  animation: _controller,
  child: new Image.network(widget.url),
  builder: (BuildContext context, Widget child) {
    return new Transform.rotate(
      angle: _controller.value * 2.0 * math.PI,
      child: child,
    );
  },
),

推荐答案

根据您的评论进行编辑，我看着进入AnimationBuilder。修改 docs 中的示例，我想到了这个可行的解决方案：

Reacting to your comment and edit I looked into the AnimationBuilder. Adapting the example in the docs I came up with this working solution:

class Spinner extends StatefulWidget {
  @override
  _SpinnerState createState() => new _SpinnerState();
}

class _SpinnerState extends State<Spinner> with SingleTickerProviderStateMixin {
  AnimationController _controller;
  CurvedAnimation _animation;

  @override
  void initState() {
    super.initState();
    _controller = new AnimationController(
      duration: const Duration(seconds: 5),
      vsync: this,
    )..forward();

    _animation = new CurvedAnimation(
        parent: _controller,
        curve: Curves.linear,
    )..addStatusListener((AnimationStatus status) {
      if (status == AnimationStatus.completed)
        print('completed');
    });
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return new AnimatedBuilder(
      animation: _animation,
      child: new Container(width: 200.0, height: 200.0, color: Colors.green),
      builder: (BuildContext context, Widget child) {
        return new Transform.rotate(
          angle: _controller.value * 2.0 * 3.1415,
          child: child,
        );
      },
    );
  }
}

如您所见，我将控制器用作父级动画，然后将其用作AnimationBuilder的动画。希望对您有所帮助。

As you can see, I used the controller as parent to an animation, which was than used as animation for the AnimationBuilder. Hope it helps.

这篇关于听动画来完成的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！