Question

onTap事件，我添加了一个动画，并从动画完成中调用了一个对话框，但问题是当我第二次点击按钮并启动动画时，对话框会打开两次，动画完成时和第三次，对话框打开3次，依此类推。

代码：

变量：

double _angle = 0;
  double _current = 0;
  AnimationController _ctrl;
  Animation _ani;

从initState（）方法初始化：

 var _duration = Duration(milliseconds: 5000);
    _ctrl = AnimationController(vsync: this, duration: _duration);
    _ani = CurvedAnimation(parent: _ctrl, curve: Curves.fastLinearToSlowEaseIn);

AnimatedBuilder：

 AnimatedBuilder(
    animation: _ani,
    builder: (context, child) {
      final _value = _ani.value;
      this.valueee=_value ;
      print("_value:$_value");
      final _angle = _value * this._angle;
      return center(
        child:GestureDetector(
           onTap : startAnimation,
           //
           //...

         ),
       ),
     },
 ),

我是从小部件树中的onTap：事件调用它的：

 startAnimation(){
    if (!_ctrl.isAnimating) {
      var _random = Random().nextDouble();
      _angle = 20 + Random().nextInt(5) + _random;
      _ctrl.forward(from: 0.0).then((_) {
        _current = (_current + _random);
        _current = _current - _current ~/ 1;
        _ctrl.reset();
        //_ctrl.stop();
      });
    }
  _ctrl.addStatusListener((status) {
      if(status == AnimationStatus.completed) {
         openDialogBox();
      }     
   }); 
}

Answer 1

每次调用startAnimation()方法时，将调用_ctrl.addStatusListener方法，然后将新的StatusListener添加到animationController。

将_ctrl.addStatusListener移到_ani = CurvedAnimation(parent: _ctrl, curve: Curves.fastLinearToSlowEaseIn);下方

像这样：

    var _duration = Duration(milliseconds: 5000);
    _ctrl = AnimationController(vsync: this, duration: _duration);
    _ani = CurvedAnimation(parent: _ctrl, curve: Curves.fastLinearToSlowEaseIn);
    _ctrl.addStatusListener((status) {
      if(status == AnimationStatus.completed) {
         openDialogBox();
      }     
   });

和

 startAnimation(){
    if (!_ctrl.isAnimating) {
      var _random = Random().nextDouble();
      _angle = 20 + Random().nextInt(5) + _random;
      _ctrl.forward(from: 0.0).then((_) {
        _current = (_current + _random);
        _current = _current - _current ~/ 1;
        _ctrl.reset();
        //_ctrl.stop();
      });
    }
}

为什么即使动画完成后也要多次打开对话框？

1 个答案: