final Tween doubleTween = new Tween<double>(begin: -200.0, end: 0.0);

_animationController = AnimationController(duration: Duration(milliseconds: 300), 
                                           
// 位移动画
_positionAnimation = Tween<double>(begin: 0, end: 50).animate(_animationController)
  ..addListener(() {
    setState(() {});
  });

// 颜色动画
_colorAnimation = ColorTween(begin: Colors.orangeAccent, end: Colors.redAccent).animate(_animationController)
  ..addListener(() {
    setState(() {});
  });
                                           
_animationController.addStatusListener((status) {
	if (status == AnimationStatus.completed) {
    print("动画完成");
  }
});

class FlutterAnimationWidget extends StatefulWidget {
  TurnTableLotteryPage({Key key}) : super(key: key);
  
  @override
  _FlutterAnimationWidgetState createState() => _FlutterAnimationWidgetState();
}

class _FlutterAnimationWidgetState extends State<FlutterAnimationWidget> with TickerProviderStateMixin {
  // ①声明位移动画控制器和颜色动画控制器以及位移动画和颜色动画
  AnimationController _animationController;
  Animation<double> _animation;
  AnimationController _colorAnimationController;
  Animation<Color> _colorAnimation;

  @override
  void initState() {
    super.initState();
    
    // ②分别创建位移、颜色的动画控制器和动画
    _animationController = AnimationController(duration: Duration(milliseconds: 300), vsync: this);
    // Tween对象调用`animate()`函数直接传入上面的AnimationController
    _animation = Tween<double>(begin: 0, end: 50).animate(_animationController)
      ..addListener(() {
        setState(() {});
      });
    _colorAnimationController = AnimationController(duration: Duration(milliseconds: 600), vsync: this);
    _colorAnimation = ColorTween(begin: Colors.orangeAccent, end: Colors.redAccent).animate(_colorAnimationController)
      ..addListener(() {
        setState(() {});
      });
    
    // ③最后,我们只需要监听位移动画完成状态之后执行颜色动画即可,
    _animationController.addStatusListener((status) {
      if (status == AnimationStatus.completed) {
        _colorAnimationController.forward();
      };
    });
  }

  void startEasyAnimation() {
    _animationController.forward();
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Container(
              width: 200,
              height: 50,
              color: _colorAnimation.value,
              margin: EdgeInsets.only(top: _animation.value),
            ),
            FlatButton(
              onPressed: startEasyAnimation,
              child: Text(
                "点击执行最简单动画",
                style: TextStyle(color: Colors.black38),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class FlutterAnimationWidget extends StatefulWidget {
  TurnTableLotteryPage({Key key}) : super(key: key);
  
  @override
  _FlutterAnimationWidgetState createState() => _FlutterAnimationWidgetState();
}

class _FlutterAnimationWidgetState extends State<FlutterAnimationWidget> with TickerProviderStateMixin {
  // ①声明一个动画Controller和多个动画.
  AnimationController _animationController;
  Animation<double> _animation;
  Animation<Color> _colorAnimation;

  @override
  void initState() {
    super.initState();
    
    // 然初始化AnimationController,AnimationController的动画时间(**duration**)要设置成所有动画的总时长,例如这里我设定为600毫秒(_animation时长:300毫秒,_colorAnimation时长:300毫秒).
    _animationController = AnimationController(duration: Duration(milliseconds: 600), vsync: this);
    // Tween对象调用`animate()`函数不再是直接传入上面的AnimationController,而是传入一个 CurvedAnimation 对象。
    // 其中CurvedAnimation构建过程中需要传入两个参数一个是 parent ,用于指定AnimationController. 另外一个是 curve,用于指定动画曲线函数.我们可以使用常用的动画曲线函数,也可以自己生成,这里我们就自己生成.指定动画执行的时间区间.
    _animation = Tween<double>(begin: 0, end: 50).animate(
      CurvedAnimation(
        parent: _animationController,
        curve: Interval(0.0, 0.5), // 由于两个动画时间长度是对分的,每一个都是300毫秒,所以 curve 参数中的值就分别是 **Interval(0.0, 0.5)**、**Interval(0.5, 1.0)**
      ),
    )..addListener(() {
        setState(() {});
      });
    _colorAnimation = ColorTween(begin: Colors.orangeAccent, end: Colors.redAccent).animate(
      CurvedAnimation(
        parent: _animationController,
        curve: Interval(0.5, 1.0),// 由于两个动画时间长度是对分的,每一个都是300毫秒,所以 curve 参数中的值就分别是 **Interval(0.0, 0.5)**、**Interval(0.5, 1.0)**
      ),
    )..addListener(() {
        setState(() {});
      });
  }

  void startEasyAnimation() {
    _animationController.forward();
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Container(
              width: 200,
              height: 50,
              color: _colorAnimation.value,
              margin: EdgeInsets.only(top: _animation.value),
            ),
            FlatButton(
              onPressed: startEasyAnimation,
              child: Text(
                "点击执行最简单动画",
                style: TextStyle(color: Colors.black38),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

const TextField({
    Key key,
    this.controller,// 文本控制器，详见下文
    this.focusNode,	// 焦点，详见下文
    this.decoration = const InputDecoration(),	// 输入框装饰器，详见下文
    TextInputType keyboardType,
    this.textInputAction,		//更改键盘本身的操作按钮，详见下文
    this.textCapitalization = TextCapitalization.none, //提供了一些有关如何使用户输入中的字母大写的选项
    this.style,
    this.textAlign = TextAlign.start,
    this.textDirection,
    this.autofocus = false,		// 是否自动获取焦点
    this.obscureText = false,	// 是否隐藏正在编辑的文本，如用于输入密码的场景等，文本内容会用“•”替换。
    this.autocorrect = true,	
    this.maxLines = 1,	// 能写入的最大行数
    this.maxLength,		// 能写入的最大字符数
    this.maxLengthEnforced = true,
    this.onChanged,				// 文本框事件：文字改变触发
    this.onEditingComplete,		// 文本框事件：当用户提交可编辑内容时调用(常用于“焦点(FocusNode)”变更)
    this.onSubmitted,			// 文本框事件：文字提交触发（键盘按键）
    this.inputFormatters,
    this.enabled,
    this.cursorWidth = 2.0,	// 光标宽度 Colors.red
    this.cursorRadius,		// 光标半径 Radius.circular(16.0)
    this.cursorColor,		// 光标颜色 16.0
    this.keyboardAppearance,
    this.scrollPadding = const EdgeInsets.all(20.0),
    this.enableInteractiveSelection = true,
    this.onTap,					// 文本框事件：
  }) : assert(textAlign != null),
       assert(autofocus != null),
       assert(obscureText != null),
       assert(autocorrect != null),
       assert(maxLengthEnforced != null),
       assert(scrollPadding != null),
       assert(maxLines == null || maxLines > 0),
       assert(maxLength == null || maxLength > 0),
       keyboardType = keyboardType ?? (maxLines == 1 ? TextInputType.text : TextInputType.multiline),
       assert(enableInteractiveSelection != null),
       super(key: key);

const InputDecoration({
    this.icon,
    this.labelText,
    this.labelStyle,
    this.helperText,
    this.helperStyle,
    this.hintText,
    this.hintStyle,
    this.errorText,
    this.errorStyle,
    this.errorMaxLines,
    this.hasFloatingPlaceholder = true,
    this.isDense,
    this.contentPadding,
    this.prefixIcon,
    this.prefix,
    this.prefixText,
    this.prefixStyle,
    this.suffixIcon,
    this.suffix,
    this.suffixText,
    this.suffixStyle,
    this.counterText,
    this.counterStyle,
    this.filled,
    this.fillColor,
    this.errorBorder,
    this.focusedBorder,
    this.focusedErrorBorder,
    this.disabledBorder,
    this.enabledBorder,
    this.border,
    this.enabled = true,
    this.semanticCounterText,
  }) : assert(enabled != null),
       assert(!(prefix != null && prefixText != null), 'Declaring both prefix and prefixText is not allowed'),
       assert(!(suffix != null && suffixText != null), 'Declaring both suffix and suffixText is not allowed'),
       isCollapsed = false;

TextField(
  textInputAction: TextInputAction.search,
),