颤振:是否可以检测出抽屉何时打开? [英] Flutter: possible to detect when a drawer is open?

问题描述

是否可以检测到抽屉何时打开，以便我们可以运行一些例程来更新其内容?

Is it possible to detect when a Drawer is open so that we can run some routine to update its content?

我的典型用例是显示关注者，喜欢者的数量...为此，我需要轮询服务器以获取此信息，然后显示它.

A typical use case I have would be to display the number of followers, likers... and for this, I would need to poll the server to get this information, then to display it.

我尝试实现NavigatorObserver来捕捉使抽屉可见/隐藏但NavigatorObserver并未检测到有关抽屉的任何情况.

I tried to implement a NavigatorObserver to catch the moment when the Drawer is made visible/hidden but the NavigatorObserver does not detect anything about the Drawer.

这是链接到NavigatorObserver的代码:

Here is the code linked to the NavigatorObserver:

import 'package:flutter/material.dart';

typedef void OnObservation(Route<dynamic> route, Route<dynamic> previousRoute);
typedef void OnStartGesture();

class NavigationObserver extends NavigatorObserver {
  OnObservation onPushed;
  OnObservation onPopped;
  OnObservation onRemoved;
  OnObservation onReplaced;
  OnStartGesture onStartGesture;

  @override
  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
    if (onPushed != null) {
      onPushed(route, previousRoute);
    }
  }

  @override
  void didPop(Route<dynamic> route, Route<dynamic> previousRoute) {
    if (onPopped != null) {
      onPopped(route, previousRoute);
    }
  }

  @override
  void didRemove(Route<dynamic> route, Route<dynamic> previousRoute) {
    if (onRemoved != null)
      onRemoved(route, previousRoute);
  }

  @override
  void didReplace({ Route<dynamic> oldRoute, Route<dynamic> newRoute }) {
    if (onReplaced != null)
      onReplaced(newRoute, oldRoute);
  }

  @override
  void didStartUserGesture() { 
    if (onStartGesture != null){
      onStartGesture();
    }
  }
}

和该观察者的初始化

void main(){
  runApp(new MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State<MyApp> {
  final NavigationObserver _observer = new NavigationObserver()
                                              ..onPushed = (Route<dynamic> route, Route<dynamic> previousRoute) {
                                                print('** pushed route: $route');
                                              }
                                              ..onPopped = (Route<dynamic> route, Route<dynamic> previousRoute) {
                                                print('** poped route: $route');
                                              }
                                              ..onReplaced = (Route<dynamic> route, Route<dynamic> previousRoute) {
                                                print('** replaced route: $route');
                                              }
                                              ..onStartGesture = () {
                                                print('** on start gesture');
                                              };

  @override
  void initState(){
    super.initState();
  }

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Title',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new SplashScreen(),
        routes: <String, WidgetBuilder> {
          '/splashscreen': (BuildContext context) => new SplashScreen(),
        },
        navigatorObservers: <NavigationObserver>[_observer],
    );
  }
}

感谢您的帮助.

推荐答案

我认为一个简单的解决方案是覆盖AppBar的leading属性，以便在按下菜单图标以运行API时可以访问以此为依据的电话.

I think one simple solution is to override the leading property of your AppBar so you can have access when the menu icon is pressed an run your API calls based on that.

但是我可能会误解了您的问题，因为使用您提供的用例，您通常需要以一种可以收听的方式来管理它，该变更将自动更新值，因此我不知道打开抽屉时要触发什么.

Yet I may have misunderstood your question because with the use case you provided, you usually need to manage it in a way that you can listen to any change which will update the value automatically so I am not sure what are you trying to trigger when the drawer is open.

无论如何，这里都是例子.

Anyway here is the example.

class DrawerExample extends StatefulWidget {
  @override
  _DrawerExampleState createState() => new _DrawerExampleState();
}

class _DrawerExampleState extends State<DrawerExample> {
  GlobalKey<ScaffoldState> _key = new GlobalKey<ScaffoldState>();
  int _counter =0;
  _handleDrawer(){
      _key.currentState.openDrawer();

           setState(() {
          ///DO MY API CALLS
          _counter++;
        });

  }
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      key: _key,
      appBar: new AppBar(
        title: new Text("Drawer Example"),
        centerTitle: true,
        leading: new IconButton(icon: new Icon(
          Icons.menu
        ),onPressed:_handleDrawer,),
      ),
      drawer: new Drawer(
        child: new Center(
          child: new Text(_counter.toString(),style: Theme.of(context).textTheme.display1,),
        ),
      ),
    );
  }
}

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