在 Flutter 中,我想制作像 Android 中的 Fragment
一样的屏幕,在我的代码中,我尝试将每个屏幕替换为当前屏幕,就像使用 Fragment.replecae
中的那样android,我使用了Hook
和Provider
,当我点击按钮在它们之间切换时,我的代码工作正常,但我无法实现返回堆栈,这意味着当我点击手机上的 Back
按钮,我的代码应该显示我存储到 _backStack
变量中的最新屏幕,此屏幕之间的每次切换我都将当前屏幕索引存储到此变量中。
如何在示例代码中从该堆栈中解回?
// Switch Between screens:
DashboardPage(), UserProfilePage(), SearchPage()
-------------> -------------> ------------->
// When back from stack:
DashboardPage(), UserProfilePage(), SearchPage()
Exit from application <-------------- <---------------- <-----------
我使用了Hook
并且我想使用这个库功能来实现这个操作
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
import 'package:provider/provider.dart';
void main() {
WidgetsFlutterBinding.ensureInitialized();
runApp(MultiProvider(providers: [
Provider.value(value: StreamBackStackSupport()),
StreamProvider<homePages>(
create: (context) =>
Provider.of<StreamBackStackSupport>(context, listen: false)
.selectedPage,
)
], child: StartupApplication()));
}
class StartupApplication extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'BackStack Support App',
home: MainBodyApp(),
);
}
}
class MainBodyApp extends HookWidget {
final List<Widget> _fragments = [
DashboardPage(),
UserProfilePage(),
SearchPage()
];
List<int> _backStack = [0];
int _currentIndex = 0;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('BackStack Screen'),
),
body: WillPopScope(
// ignore: missing_return
onWillPop: () {
customPop(context);
},
child: Container(
child: Column(
children: <Widget>[
Consumer<homePages>(
builder: (context, selectedPage, child) {
_currentIndex = selectedPage != null ? selectedPage.index : 0;
_backStack.add(_currentIndex);
return Expanded(child: _fragments[_currentIndex]);
},
),
Container(
width: double.infinity,
height: 50.0,
padding: const EdgeInsets.symmetric(horizontal: 15.0),
color: Colors.indigo[400],
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
RaisedButton(
onPressed: () => Provider.of<StreamBackStackSupport>(
context,
listen: false)
.switchBetweenPages(homePages.screenDashboard),
child: Text('Dashboard'),
),
RaisedButton(
onPressed: () => Provider.of<StreamBackStackSupport>(
context,
listen: false)
.switchBetweenPages(homePages.screenProfile),
child: Text('Profile'),
),
RaisedButton(
onPressed: () => Provider.of<StreamBackStackSupport>(
context,
listen: false)
.switchBetweenPages(homePages.screenSearch),
child: Text('Search'),
),
],
),
),
],
),
),
),
);
}
void navigateBack(int index) {
useState(() => _currentIndex = index);
}
void customPop(BuildContext context) {
if (_backStack.length - 1 > 0) {
navigateBack(_backStack[_backStack.length - 1]);
} else {
_backStack.removeAt(_backStack.length - 1);
Provider.of<StreamBackStackSupport>(context, listen: false)
.switchBetweenPages(homePages.values[_backStack.length - 1]);
Navigator.pop(context);
}
}
}
class UserProfilePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
alignment: Alignment.center,
child: Text(' screenProfile ...'),
);
}
}
class DashboardPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
alignment: Alignment.center,
child: Text(' screenDashboard ...'),
);
}
}
class SearchPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
alignment: Alignment.center,
child: Text(' screenSearch ...'),
);
}
}
enum homePages { screenDashboard, screenProfile, screenSearch }
class StreamBackStackSupport {
final StreamController<homePages> _homePages = StreamController<homePages>();
Stream<homePages> get selectedPage => _homePages.stream;
void switchBetweenPages(homePages selectedPage) {
_homePages.add(homePages.values[selectedPage.index]);
}
void close() {
_homePages.close();
}
}
最佳答案
TL;DR
完整代码在最后。
使用Navigator
相反
您应该以不同的方式解决这个问题。我可以向您提供一个适合您的方法的解决方案,但是,我认为您应该通过实现自定义 Navigator
来解决这个问题 因为这是 Flutter 中的内置解决方案。
当您使用Navigator
时,您不需要任何基于流的管理,即您可以删除 StreamBackStackSupport
完全。
现在,您插入 Navigator
您拥有Consumer
的小部件之前:
children: <Widget>[
Expanded(
child: Navigator(
...
),
),
Container(...), // Your bottom bar..
]
导航器使用字符串管理其路线,这意味着我们需要有一种方法来转换您的 enum
(我将其重命名为 Page
)到 String
s。我们可以使用 describeEnum
为此并将其放入 extension
:
enum Page { screenDashboard, screenProfile, screenSearch }
extension on Page {
String get route => describeEnum(this);
}
现在,您可以使用例如获取页面的字符串表示形式: Page.screenDashboard.route
.
此外,您希望将实际页面映射到片段小部件,您可以这样做:
class MainBodyApp extends HookWidget {
final Map<Page, Widget> _fragments = {
Page.screenDashboard: DashboardPage(),
Page.screenProfile: UserProfilePage(),
Page.screenSearch: SearchPage(),
};
...
访问Navigator
,我们需要有一个 GlobalKey
。通常我们会有 StatefulWidget
并管理GlobalKey
像那样。既然你想使用 flutter_hooks
,我选择使用 GlobalObjectKey
相反:
@override
Widget build(BuildContext context) {
final navigatorKey = GlobalObjectKey<NavigatorState>(context);
...
现在,您可以使用navigatorKey.currentState
小部件中的任何位置都可以访问此自定义导航器。完整Navigator
设置如下所示:
Navigator(
key: navigatorKey,
initialRoute: Page.screenDashboard.route,
onGenerateRoute: (settings) {
final pageName = settings.name;
final page = _fragments.keys.firstWhere((element) => describeEnum(element) == pageName);
return MaterialPageRoute(settings: settings, builder: (context) => _fragments[page]);
},
)
如您所见,我们通过 navigatorKey
之前创建并定义 initialRoute
,利用route
我们创建的扩展。在 onGenerateRoute
,我们找到Page
与路由名称(a String
)相对应的枚举条目,然后返回 MaterialPageRoute
与适当的_fragments
条目。
要推送新路线,您只需使用 navigatorKey
和 pushNamed
:
onPressed: () => navigatorKey.currentState.pushNamed(Page.screenDashboard.route),
后退按钮
我们还需要自定义调用 pop
在我们的自定义导航器上。为此, WillPopScope
需要:
WillPopScope(
onWillPop: () async {
if (navigatorKey.currentState.canPop()) {
navigatorKey.currentState.pop();
return false;
}
return true;
},
child: ..,
)
访问嵌套页面内的自定义导航器
在传递到 onGenerateRoute
的任何页面中,即在您的任何“片段”中,您只需调用 Navigator.of(context)
而不是使用全局 key 。这是可能的,因为这些路线是自定义导航器的子路线,因此 BuildContext
包含该自定义导航器。
例如:
// In SearchPage
Navigator.of(context).pushNamed(Page.screenProfile.route);
默认导航器
您可能想知道如何访问 MaterialApp
现在根导航器,例如推新的全屏路线。您可以使用 findRootAncestorStateOfType
为此:
context.findRootAncestorStateOfType<NavigatorState>().push(..);
或者简单地
Navigator.of(context, rootNavigator: true).push(..);
<小时/>
完整代码如下:
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
void main() {
runApp(StartupApplication());
}
enum Page { screenDashboard, screenProfile, screenSearch }
extension on Page {
String get route => describeEnum(this);
}
class StartupApplication extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'BackStack Support App',
home: MainBodyApp(),
);
}
}
class MainBodyApp extends HookWidget {
final Map<Page, Widget> _fragments = {
Page.screenDashboard: DashboardPage(),
Page.screenProfile: UserProfilePage(),
Page.screenSearch: SearchPage(),
};
@override
Widget build(BuildContext context) {
final navigatorKey = GlobalObjectKey<NavigatorState>(context);
return WillPopScope(
onWillPop: () async {
if (navigatorKey.currentState.canPop()) {
navigatorKey.currentState.pop();
return false;
}
return true;
},
child: Scaffold(
appBar: AppBar(
title: Text('BackStack Screen'),
),
body: Container(
child: Column(
children: <Widget>[
Expanded(
child: Navigator(
key: navigatorKey,
initialRoute: Page.screenDashboard.route,
onGenerateRoute: (settings) {
final pageName = settings.name;
final page = _fragments.keys.firstWhere(
(element) => describeEnum(element) == pageName);
return MaterialPageRoute(settings: settings,
builder: (context) => _fragments[page]);
},
),
),
Container(
width: double.infinity,
height: 50.0,
padding: const EdgeInsets.symmetric(horizontal: 15.0),
color: Colors.indigo[400],
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
RaisedButton(
onPressed: () => navigatorKey.currentState
.pushNamed(Page.screenDashboard.route),
child: Text('Dashboard'),
),
RaisedButton(
onPressed: () => navigatorKey.currentState
.pushNamed(Page.screenProfile.route),
child: Text('Profile'),
),
RaisedButton(
onPressed: () => navigatorKey.currentState
.pushNamed(Page.screenSearch.route),
child: Text('Search'),
),
],
),
),
],
),
),
),
);
}
}
class UserProfilePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
alignment: Alignment.center,
child: Text(' screenProfile ...'),
);
}
}
class DashboardPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
alignment: Alignment.center,
child: Text(' screenDashboard ...'),
);
}
}
class SearchPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
alignment: Alignment.center,
child: Text(' screenSearch ...'),
);
}
}
关于flutter - 使用导航和堆栈将多个页面实现为单个页面,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60901865/