文章目录
一、Flutter 应用生命周期二、监听 Flutter 应用生命周期三、完整代码示例四、相关资源一、Flutter 应用生命周期
应用生命周期 :
resumed: 应用进入前台 ;paused: 应用进入后台 ;inactive: 应用进入非活动状态 ;detached: 应用在运行但与组件分离 ;
Flutter 应用生命周期状态枚举 :该枚举中四个生命周期状态 , 源码注释中详细说明了每个状态的用法 ;
/// States that an application can be in.////// The values below describe notifications from the operating system./// Applications should not expect to always receive all possible/// notifications. For example, if the users pulls out the battery from the/// device, no notification will be sent before the application is suddenly/// terminated, along with the rest of the operating system.////// See also:////// * [WidgetsBindingObserver], for a mechanism to observe the lifecycle state/// from the widgets layer.enum AppLifecycleState {/// The application is visible and responding to user input.resumed,/// The application is in an inactive state and is not receiving user input.////// On iOS, this state corresponds to an app or the Flutter host view running/// in the foreground inactive state. Apps transition to this state when in/// a phone call, responding to a TouchID request, when entering the app/// switcher or the control center, or when the UIViewController hosting the/// Flutter app is transitioning.////// On Android, this corresponds to an app or the Flutter host view running/// in the foreground inactive state. Apps transition to this state when/// another activity is focused, such as a split-screen app, a phone call,/// a picture-in-picture app, a system dialog, or another window.////// Apps in this state should assume that they may be [paused] at any time.inactive,/// The application is not currently visible to the user, not responding to/// user input, and running in the background.////// When the application is in this state, the engine will not call the/// [Window.onBeginFrame] and [Window.onDrawFrame] callbacks.paused,/// The application is still hosted on a flutter engine but is detached from/// any host views.////// When the application is in this state, the engine is running without/// a view. It can either be in the progress of attaching a view when engine/// was first initializes, or after the view being destroyed due to a Navigator/// pop.detached,}
二、监听 Flutter 应用生命周期
监听 Flutter 应用生命周期 , 需要在页面 StatefulWidget 的 initState 页面生命周期函数中注册 WidgetsBindingObserver 观察者 ;
@overridevoid initState() {super.initState();/// 如果想要监听应用生命周期 , 要先绑定观察者 ,/// 绑定完成后 , 如果应用生命周期发生了变化 ,/// 就会回调 didChangeAppLifecycleState 方法 ;WidgetsBinding.instance.addObserver(this);}
注册了 WidgetsBindingObserver 观察者之后 , 在应用生命周期改变时 , 就会回调 WidgetsBindingObserver 类的 didChangeAppLifecycleState 方法 , 其 AppLifecycleState state 参数就是当前的应用生命周期状态 ;
/// 当应用生命周期发生变化时 , 会回调该方法@overridevoid didChangeAppLifecycleState(AppLifecycleState state) {super.didChangeAppLifecycleState(state);print("当前的应用生命周期状态 : ${state}");if(state == AppLifecycleState.paused){print("应用进入后台 paused");}else if(state == AppLifecycleState.resumed){print("应用进入前台 resumed");}else if(state == AppLifecycleState.inactive){// 应用进入非活动状态 , 如来了个电话 , 电话应用进入前台// 本应用进入该状态print("应用进入非活动状态 inactive");}else if(state == AppLifecycleState.detached){// 应用程序仍然在 Flutter 引擎上运行 , 但是与宿主 View 组件分离print("应用进入 detached 状态 detached");}}
在 StatefulWidget 页面销毁时需要移除该 WidgetsBindingObserver 观察者 ;
/// 移出组件中注册的观察者@overridevoid dispose() {super.dispose();WidgetsBinding.instance.removeObserver(this);}
三、完整代码示例
完整代码示例 :
import 'package:flutter/material.dart';class AppLifeCyclePage extends StatefulWidget {@override_AppLifeCyclePageState createState() => _AppLifeCyclePageState();}class _AppLifeCyclePageState extends State<AppLifeCyclePage> with WidgetsBindingObserver {@overridevoid initState() {super.initState();/// 如果想要监听应用生命周期 , 要先绑定观察者 ,/// 绑定完成后 , 如果应用生命周期发生了变化 ,/// 就会回调 didChangeAppLifecycleState 方法 ;WidgetsBinding.instance.addObserver(this);}@overrideWidget build(BuildContext context) {return Scaffold(appBar: AppBar(// 标题title: Text("应用生命周期"),// 返回按钮leading: BackButton(),),body: Container(// 居中设置alignment: Alignment.center,child: Text("应用生命周期"),),);}/// 移出组件中注册的观察者@overridevoid dispose() {super.dispose();WidgetsBinding.instance.removeObserver(this);}/// 当应用生命周期发生变化时 , 会回调该方法@overridevoid didChangeAppLifecycleState(AppLifecycleState state) {super.didChangeAppLifecycleState(state);print("当前的应用生命周期状态 : ${state}");if(state == AppLifecycleState.paused){print("应用进入后台 paused");}else if(state == AppLifecycleState.resumed){print("应用进入前台 resumed");}else if(state == AppLifecycleState.inactive){// 应用进入非活动状态 , 如来了个电话 , 电话应用进入前台// 本应用进入该状态print("应用进入非活动状态 inactive");}else if(state == AppLifecycleState.detached){// 应用程序仍然在 Flutter 引擎上运行 , 但是与宿主 View 组件分离print("应用进入 detached 状态 detached");}}}
运行效果 :
进入界面 :进入界面后 , 由于还没有注册 WidgetsBindingObserver , 因此不打印日志 , 等界面加载完毕后 , 进行各种操作 ( 如按下 Home 键 , 按下回退键 , 按下菜单键 ) 时才打印日志 ;
按下菜单键 :
界面状态 :打印日志 :
I/flutter (30370): 当前的应用生命周期状态 : AppLifecycleState.inactiveI/flutter (30370): 应用进入非活动状态 inactiveD/FlutterView(30370): Detaching from a FlutterEngine: io.flutter.embedding.engine.FlutterEngine@9d12774I/flutter (30370): 当前的应用生命周期状态 : AppLifecycleState.pausedI/flutter (30370): 应用进入后台 paused
再次点击回到应用界面 :
界面状态 :打印日志 :
I/flutter (30370): 当前的应用生命周期状态 : AppLifecycleState.resumedI/flutter (30370): 应用进入前台 resumedD/FlutterView(30370): Attaching to a FlutterEngine: io.flutter.embedding.engine.FlutterEngine@9d12774
完整日志 :
# 按下菜单键I/flutter (30370): 当前的应用生命周期状态 : AppLifecycleState.inactiveI/flutter (30370): 应用进入非活动状态 inactiveD/FlutterView(30370): Detaching from a FlutterEngine: io.flutter.embedding.engine.FlutterEngine@9d12774I/flutter (30370): 当前的应用生命周期状态 : AppLifecycleState.pausedI/flutter (30370): 应用进入后台 paused# 返回界面I/flutter (30370): 当前的应用生命周期状态 : AppLifecycleState.resumedI/flutter (30370): 应用进入前台 resumedD/FlutterView(30370): Attaching to a FlutterEngine: io.flutter.embedding.engine.FlutterEngine@9d12774
四、相关资源
参考资料 :
Flutter 官网 :https://flutter.dev/Flutter 插件下载地址 :https://pub.dev/packagesFlutter 开发文档 :/docs( 强烈推荐 )官方 GitHub 地址: /flutterFlutter 中文社区 :/Flutter 实用教程 :/docs/cookbookFlutter CodeLab :https://codelabs.flutter-/Dart 中文文档 :/Dart 开发者官网 :https://api.dart.dev/Flutter 中文网 ( 非官方 , 翻译的很好 ) :https://flutterchina.club/ , /docs/Flutter 相关问题 :https://flutterchina.club/faq/ ( 入门阶段推荐看一遍 )
博客源码下载 :
GitHub 地址 :/han120/flutter_cmd ( 随博客进度一直更新 , 有可能没有本博客的源码 )
博客源码快照 :/download/han120/15547438 ( 本篇博客的源码快照 , 可以找到本博客的源码 )
【Flutter】Flutter 应用生命周期 ( 前台状态 resumed | 后台状态 paused | 非活动状态 inactive | 组件分离状态 detached )
