老孟導讀：在 Flutter 1.17 釋出大會上，Flutter 團隊還發布了新的 Animations 軟體包，該軟體包提供了實現新的 Material motion 規範的預構建動畫。
軟體包 pub 地址：pub.dev/packages/an…
Material motion 規範：material.io/design/moti…
引入外掛，版本號請到 pub 上檢視最新版本號：
animations: ^1.1.1複製程式碼Container transform
容器轉換模式設計用於包含容器的UI元素之間的轉換。此模式在兩個UI元素之間建立可見連線。
案例：構建GridView，點選其中一項時跳轉到期詳情頁面：
GridView.builder(
padding: EdgeInsets.all(8),
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 2, crossAxisSpacing: 2, mainAxisSpacing: 4),
itemBuilder: (context, index) {
return OpenContainer(
transitionDuration: _duration,
closedBuilder: (BuildContext _, VoidCallback openContainer) {
return Container(
child: Image.asset(
'assets/images/b.jpg',
fit: BoxFit.fitWidth,
),
);
},
openBuilder: (BuildContext context, VoidCallback _) {
return _DetailPage();
},
);
},
itemCount: 50,
)複製程式碼使用 OpenContainer 元件，closedBuilder 表示關閉狀態時到元件，在這裡表示 GridView Item，openBuilder 表示點選要跳轉的頁面，這裡表示詳情頁面。
詳情頁面程式碼如下：
class _DetailPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: Container(
width: double.infinity,
height: double.infinity,
child: Image.asset(
'assets/images/b.jpg',
fit: BoxFit.cover,
),
),
);
}
}複製程式碼
構建ListView
ListView.builder(
itemBuilder: (context, index) {
return OpenContainer(
transitionDuration: _duration,
closedBuilder: (BuildContext _, VoidCallback openContainer) {
return Card(
child: Container(
height: 45,
alignment: Alignment.center,
child: Text('$index'),
),
);
},
openBuilder: (BuildContext context, VoidCallback _) {
return _DetailPage();
},
);
},
itemCount: 50,
)複製程式碼
也可以是一個按鈕，比如 floatingActionButton
Scaffold(
body: _buildListView(),
floatingActionButton: OpenContainer(
openBuilder: (BuildContext context, VoidCallback _) {
return _DetailPage();
},
transitionDuration: _duration,
closedElevation: 6.0,
closedShape: const RoundedRectangleBorder(
borderRadius: BorderRadius.all(
Radius.circular(50),
),
),
closedColor: Theme.of(context).colorScheme.secondary,
closedBuilder: (BuildContext context, VoidCallback openContainer) {
return SizedBox(
height: 50,
width: 50,
child: Center(
child: Icon(
Icons.add,
color: Theme.of(context).colorScheme.onSecondary,
),
),
);
},
),
)複製程式碼
頂部輸入框
Scaffold(
appBar: AppBar(
title: OpenContainer(
transitionDuration: _duration,
closedBuilder: (BuildContext _, VoidCallback openContainer) {
return Container(
width: 300,
height: 45,
padding: EdgeInsets.only(left: 5),
decoration: BoxDecoration(
border: Border.all(color: Colors.grey.withOpacity(.5))),
alignment: Alignment.centerLeft,
child: Icon(Icons.search,color: Colors.black,),
);
},
openBuilder: (BuildContext context, VoidCallback _) {
return _DetailPage();
},
),
),
)複製程式碼
Shared axis
共享軸模式用於具有空間或導航關係的UI元素之間的過渡。此模式在x，y或z軸上使用共享的變換來加強元素之間的關係。
底部導航案例：
@override
Widget build(BuildContext context) {
Widget _child = _OnePage();
switch (_currentIndex) {
case 1:
_child = _TwoPage();
break;
}
return Scaffold(
body: PageTransitionSwitcher(
duration: const Duration(milliseconds: 1500),
reverse: false,
transitionBuilder: (
Widget child,
Animation<double> animation,
Animation<double> secondaryAnimation,
) {
return SharedAxisTransition(
child: child,
animation: animation,
transitionType: SharedAxisTransitionType.horizontal,
secondaryAnimation: secondaryAnimation,
);
},
child: _child,
),
bottomNavigationBar: BottomNavigationBar(
onTap: (int index) {
setState(() {
_currentIndex = index;
});
},
currentIndex: _currentIndex,
items: <BottomNavigationBarItem>[
BottomNavigationBarItem(title: Text('首頁'), icon: Icon(Icons.home)),
BottomNavigationBarItem(
title: Text('我的'), icon: Icon(Icons.perm_identity)),
],
),
);
}複製程式碼
型別為 y 軸：
transitionType: SharedAxisTransitionType.vertical,複製程式碼
型別為 z 軸：
transitionType: SharedAxisTransitionType.scaled,複製程式碼
Fade through
淡入模式用於彼此之間沒有密切關係的UI元素之間的過渡。
下面案例來源於官方Demo：
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('Fade through')),
body: PageTransitionSwitcher(
transitionBuilder: (
Widget child,
Animation<double> animation,
Animation<double> secondaryAnimation,
) {
return FadeThroughTransition(
animation: animation,
secondaryAnimation: secondaryAnimation,
child: child,
);
},
child: pageList[pageIndex],
),
bottomNavigationBar: BottomNavigationBar(
currentIndex: pageIndex,
onTap: (int newValue) {
setState(() {
pageIndex = newValue;
});
},
items: const <BottomNavigationBarItem>[
BottomNavigationBarItem(
icon: Icon(Icons.photo_library),
title: Text('Albums'),
),
BottomNavigationBarItem(
icon: Icon(Icons.photo),
title: Text('Photos'),
),
BottomNavigationBarItem(
icon: Icon(Icons.search),
title: Text('Search'),
),
],
),
);
}複製程式碼
效果適用於：
- 底部導航切換。
- 重新整理列表。
- 切換器。
Fade
淡入淡出模式用於在螢幕範圍內進入或退出的UI元素，例如在螢幕中央淡入淡出的對話方塊。
彈出對話方塊案例：
Scaffold(
body: Center(
child: RaisedButton(
onPressed: () {
showModal<void>(
context: context,
builder: (BuildContext context) {
return AlertDialog(
content: const Text('對話方塊'),
actions: <Widget>[
FlatButton(
onPressed: () {
Navigator.of(context).pop();
},
child: const Text('取消'),
),
FlatButton(
onPressed: () {
Navigator.of(context).pop();
},
child: const Text('確定'),
),
],
);
},
);
},
color: Theme.of(context).colorScheme.primary,
textColor: Theme.of(context).colorScheme.onPrimary,
child: const Text('彈出對話方塊'),
),
),
)複製程式碼
適用場景：
- dialog
- menu
- snackbar
- FloatingActionButton
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