二 为什么要监听路由堆栈变化

---

• 当由页面A跳转到页面B时，堆栈及状态发生了变化

• 页面跳转时的变化状态有：didPush(跳转)/didPushNext(下一个)、didPop(返回)/didPopNext(返回上一个)

• 通过路由堆栈监听，可以自定义路由堆栈，方便分析异常日志等

三 如何监听路由堆栈

---

3.1 几个关键字

navigatorObservers(路由监听列表)

const MaterialApp({

Key? key,

Map<String, WidgetBuilder> th

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is.routes = const <String, WidgetBuilder>{},

this.initialRoute,

List this.navigatorObservers = const [],

}

• MaterialApp的一个属性，用于监听StatefulWidget的路由状态

• navigatorObservers接收一个RouteObserver数组

RouteObserver(路由监听)

class RouteObserver<R extends Route> extends NavigatorObserver {

final Map<R, Set> _listeners = <R, Set>{};

/// Subscribe [routeAware] to be informed about changes to [route].

}

• 继承NavigatorObserver，监听页面的路由变化

• 通过RouteAware接口回调通知状态变化

• 接收参数Route

Route

• 抽象类，定义路由信息(RouteSettings)

• 常用子类有：ModalRoute、PageRoute等

RouteAware

• 接口，定义路由的状态回调

• 接口方法有：didPop、didPopNext、didPush、didPushNext

• 通过State<StatefulWidget>with RouteAware监听状态，并回调上面接口中的方法

3.2 路由监听

开始监听

@override

void didChangeDependencies() {

super.didChangeDependencies();

routeObserver.subscribe(this, ModalRoute.of(context));

}

结束监听

@override

void dispose() {

super.dispose();

routeObserver.unsubscribe(this);

}

四 路由堆栈示例

---

4.1 示例一(从A页面跳转路由监听页面)

** MaterialApp组件中添加**

RouteObserver routeObserver=RouteObserver();

class MyApp extends StatelessWidget {

@override

Widget build(BuildContext context) {

return MaterialApp(

routes: <String, WidgetBuilder>{

“/M”:(context)=>MyApp(),

“/B”:(context)=>BPage(),

“/C”:(context)=>CPage(),

“/D”:(context)=>DPage(),

“/P”:(context)=>ProductDetail(),

“/ARouteObserver”:(context)=>ARouteObserverDemo(),

“/BRouteObserver”:(context)=>BRouteObserverDemo(),

},

navigatorObservers: [routeObserver],

title: ‘Flutter Demo’,

theme: ThemeData(primarySwatch: Colors.blue,),

home: MyHomePage(title: ‘Flutter Demo Home Page’),

);

}

}

路由监听

class ARouteObserverDemo extends StatefulWidget {

@override

_RouteObserverDemoState createState() => _RouteObserverDemoState();

}

class _RouteObserverDemoState extends State with RouteAware {

@override

void didChangeDependencies() {

super.didChangeDependencies();

routeObserver.subscribe(this, ModalRoute.of(context));

}

@override

Widget build(BuildContext context) {

return Scaffold(

body: Container(

alignment: Alignment.center,

child: RaisedButton(

child: Text(‘A RouteObserver’),

onPressed: () {

Navigator.of(context).pushNamed(’/BRouteObserver’);

},

),

),

);

}

@override

void dispose() {

super.dispose();

routeObserver.unsubscribe(this);

}

@override

void didPush() {

final route = ModalRoute.of(context).settings.name;

print(‘A-didPush route: $route’);

}

@override

void didPopNext() {

final route = ModalRoute.of(context).settings.name;

print(‘A-didPopNext route: $route’);

}

@override

void didPushNext() {

final route = ModalRoute.of(context).settings.name;

print(‘A-didPushNext route: $route’);

}

@override

void didPop() {

final route = ModalRoute.of(context).settings.name;

print(‘A-didPop route: $route’);

}

}

其中 didPush、didPushNext、didPopNext、didPop 为路由堆栈变化的回调。

页面跳转及打印

从 A 页面跳转到 ARouteObserverDemo 页面，日志输出如下

flutter: A-didPush route: /ARouteObserver

进入此页面只调用了 didPush

4.2 示例二(从路由监听A页面跳转路由监听B页面)

路由监听B页面(MaterialApp及A页面同上)

class _BRouteObserverDemo extends State with RouteAware {