前语

目前正在做的项目，为了添加用户的体会度，预备添加一些动画作用，其间底部栏中间按钮的点击事情参考了闲鱼的动效，便在此基础上仿写了该动效，并添加了一些新的作用。

动效

闲鱼动效

仿写作用

思路

根据UI的规划图，对每个模块规划好动画作用，本人主要规划了以下四个作用。

1、底部回来键旋转动画

底部回来按钮动画其实便是个旋转动画，使用Transform.rotate设置angle的值即可，这儿使用了GetX来对angle进行动态控制。

//回来键旋转角度，初始旋转45度，使其初始款式为 +
var angle = (pi / 4).obs;
///封闭按钮旋转动画控制器
late final AnimationController closeController;
late final Animation<double> closeAnimation;
///回来键旋转动画
closeController = AnimationController(
  duration: const Duration(milliseconds: 300),
  vsync: provider,
);
///回来键旋转动画
closeController = AnimationController(
  duration: const Duration(milliseconds: 300),
  vsync: provider,
);
///页面渲染完才开端执行，不然第一次翻开不会启动动画
WidgetsBinding.instance.addPostFrameCallback((duration) {
  closeAnimation =
      Tween(begin: pi / 4, end: pi / 2).animate(closeController)
        ..addListener(() {
          angle.value = closeAnimation.value;
        });
  closeController.forward();
});
///封闭按钮点击事情
void close() {
  ///反转动画，并封闭页面
  Future.delayed(
     const Duration(milliseconds: 120), () {
    Get.back();
  });
  closeController.reverse();
}
IconButton(
    onPressed: null,
    alignment: Alignment.center,
    icon: Transform.rotate(
      angle: controller.angle.value,
      child: SvgPicture.asset(
        "assets/user/ic-train-car-close.svg",
        width: 18,
        height: 18,
        color: Colors.black,
      ),
    ))

2、底部四个栏目变速上移动画+突变动画

四个栏目其实便是个平移动画，只不过闲鱼是四个栏目一同平移，而我选择了变速平移，这样视觉作用上会好一点。

//透明度变化
List<AnimationController> opacityControllerList = [];
//上移动画，因为每个栏目的移动速度不一样，需要用List保存四个AnimationController，
//如果想像闲鱼那种全体上移，则只用一个AnimationController即可。
List<AnimationController> offsetControllerList = [];
List<Animation<Offset>> offsetAnimationList = [];
//之所以用addIf，是因为项目中这几个栏目的显现是动态显现的，这儿就直接写成true
Column(
    children: []
      ..addIf(
          true,
          buildItem('assets/user/ic-train-nomal-car.webp',"学车加练","自主预约，快速拿证"))
      ..addIf(
          true,
          buildItem('assets/user/ic-train-fuuxn-car.webp',"有证复训","优质陪练，轻松驾车"))
      ..addIf(
          true,
          buildItem('assets/user/ic-train-jiaxun-car.webp',"模仿加训","考前加训，临考不惧"))
      ..addIf(
          true,
          buildItem('assets/user/ic-train-jiakao-car.webp',"驾考报名","快捷报名无门槛"))
      ..add(playWidget())
      ..addAll([
        17.space,
      ]),
   )
//只是是为了在offsetController全部初始化完后执行play()
Widget playWidget() {
  //执行动画
  play();
  return Container();
}
int i = 0;
Widget buildItem(String img,String tab,String slogan) {
  //因为底部栏目是动态显现的，需要在创建Widget时一同创建offsetController和offsetAnimation
  i++;
  AnimationController offsetController = AnimationController(
    duration: Duration(milliseconds: 100 + i * 20),
    vsync: this,
  );
  Animation<Offset> offsetAnimation = Tween<Offset>(
    begin: const Offset(0, 2.5),
    end: const Offset(0, 0),
  ).animate(CurvedAnimation(
    parent: offsetController,
    // curve: Curves.easeInOutSine,
    curve: const Cubic(0.12, 0.28, 0.48, 1),
  ));
  AnimationController opacityController = AnimationController(
      duration: const Duration(milliseconds: 500),
      lowerBound: 0.2,
      upperBound: 1.0,
      vsync: this);
  opacityControllerList.add(opacityController);
  offsetControllerList.add(offsetController);
  offsetAnimationList.add(offsetAnimation);
  return SlideTransition(
    position: offsetAnimation,
    child: FadeTransition(
        opacity: opacityController,
        child: Container(
            margin: EdgeInsets.only(bottom: 16),
            height: 62,
            decoration: BoxDecoration(
                borderRadius: BorderRadius.all(Radius.circular(12)),
                color: const Color(0xfffafafa)),
            child:
            Row(mainAxisAlignment: MainAxisAlignment.center, children: [
              24.space,
              Image.asset(img, width: 44, height: 44),
              12.space,
              Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    Text(tab,
                        style: const TextStyle(
                            color: Color(0XFF000000),
                            fontSize: 16,
                            fontWeight: FontWeight.bold)),
                    Text(slogan,
                        style: const TextStyle(
                            color: Color(0XFF6e6e6e), fontSize: 12)),
                  ]).expanded,
              Image.asset("assets/user/ic-train-arrow.webp",
                  width: 44, height: 44),
              17.space
            ])).inkWell(
            onTap: () {},
            delayMilliseconds: 50)),
  );
}
//执行动画
void play() async {
  for (int i = 0; i < offsetControllerList.length; i++) {
    opacityControllerList[i].forward();
    ///栏目正序顺次推迟(40 + 2 * i) * i的时刻,曲线速率
    Future.delayed(Duration(milliseconds: (40 + 2 * i) * i), () {
      offsetControllerList[i]
          .forward()
          .whenComplete(() => offsetControllerList[i].stop());
    });
  }
}
///封闭按钮点击事情
void close() {
  ///反转动画，并封闭页面
  Future.delayed(
     const Duration(milliseconds: 120), () {
    Get.back();
  });
  for (int i = offsetControllerList.length - 1; i >= 0; i--) {
    ///栏目倒叙顺次推迟(40 + 2 * (offsetControllerList.length-1-i)) * (offsetControllerList.length-1-i))的时刻
    Future.delayed(
        Duration(
            milliseconds:
            (40 + 2 * (offsetControllerList.length-1-i)) * (offsetControllerList.length-1-i)), () {
      offsetControllerList[i].reverse();
    });
  }
  opacityTopController.reverse();
}

3、中间图片突变动画

突变动画使用FadeTransition即可。

///图片透明度突变动画控制器
late final AnimationController imgController;
///图片透明度突变动画
imgController = AnimationController(
    duration: const Duration(milliseconds: 500),
    lowerBound: 0.0,
    upperBound: 1.0,
    vsync: provider);
imgController.forward().whenComplete(() => imgController.stop());
///突变过渡
FadeTransition(
  opacity: imgController,
  child:
  Image.asset("assets/user/ic-traincar-guide.webp"),
),
///封闭按钮点击事情
void close() {
  imgController.reverse();
}

4、顶部文案突变动画+下移动画

///顶部标题下移动画控制器
late final AnimationController offsetTopController;
late final Animation<Offset> offsetTopAnimation;
///顶部标题突变动画控制器
late final AnimationController opacityTopController;
///顶部标题上移动画
offsetTopController = AnimationController(
  duration: const Duration(milliseconds: 300),
  vsync: provider,
);
offsetTopController
    .forward()
    .whenComplete(() => offsetTopController.stop());
offsetTopAnimation = Tween<Offset>(
  begin: const Offset(0, -0.8),
  end: const Offset(0, 0),
).animate(CurvedAnimation(
  parent: offsetTopController,
  curve: Curves.easeInOutCubic,
));
offsetTopController
    .forward()
    .whenComplete(() => offsetTopController.stop());
//UI
SlideTransition(
    position: offsetTopAnimation,
    child: FadeTransition(
        opacity: opacityTopController,
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          mainAxisAlignment: MainAxisAlignment.start,
          mainAxisSize: MainAxisSize.min,
          children: [
            80.space,
            const Text(
              '练车攻略',
              style: TextStyle(
                color: Color(0XFF141414),
                fontSize: 32,
                fontWeight: FontWeight.w800,
              ),
            ),
            2.space,
            const Text('易练只为您提供优质教练，为您的安全保驾护航',
                style: TextStyle(
                    color: Color(0XFF141414),
                    fontSize: 15)),
          ],
        ))),
///封闭按钮点击事情
void close() {
  offsetTopController.reverse();
  opacityTopController.reverse();
}

5、刊出动画

最后，在封闭页面的时分不要忘记刊出动画。

///封闭时刊出动画
void dispose() {
  for (int i = offsetControllerList.length - 1; i > 0; i--) {
    offsetControllerList[i].dispose();
  }
  offsetTopController.dispose();
  opacityTopController.dispose();
  imgController.dispose();
  closeController.dispose();
}