Android LifeCycle监控生命周期

本文主要是介绍Android LifeCycle监控生命周期，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

LifeCycle的作用是感知组件(Activity/Fragment)的生命周期 , 并在合适的生命周期执行分配的任务.

1.监听组件生命后期

假设我们此时有一个Util类,其中有两个方法需要分别在Activity的onStart和onDestory的时候执行,我们可以先让它实现LifecycleObserver:

class LifecycleUtil : LifecycleObserver {@OnLifecycleEvent(androidx.lifecycle.Lifecycle.Event.ON_START)fun startFun() {}@OnLifecycleEvent(androidx.lifecycle.Lifecycle.Event.ON_STOP)fun stopFun() {}
}

然后对于任何实现了LifecycleOwner接口的生命周期组件，如果需要使用该Util的话，只需要添加如下一行代码即可。

lifecycle.addObserver(LocationUtil( ))

class MyActivity : AppCompatActivity(), LifecycleOwner {override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContentView(R.layout.activity_my)lifecycle.addObserver(LifecycleUtil())}
}

LifeCycle让LifecycleUtil这种第三方组件在自己的内部就可以拿到生命周期,这样原来需要写在Activity/Fragment中内部逻辑处理,在组件内部就可以独立完成,进一步解耦.

如果此时需要将LifecycleUtil的两个方法放到其他生命周期去执行,也只需改一下注解就好了,外部无需任何修改.

2.监听应用前后台切换

一些App都有在应用切换到后台时弹出一个toast,提示你正在后台运行,用Lifecycle实现很简单,同样是使用Lifecycle.Event的ON_Start和ON_STOP.

然后在应用启动时 , 在ContentProvider或Application中调用如下代码:
ProcessLifecycleOwner.get().lifecycle.addObserver(LifecycleUtil())

class MyApplication : Application() {override fun onCreate() {super.onCreate()ProcessLifecycleOwner.get().lifecycle.addObserver(LifecycleUtil())}
}

ProcessLifecycleOwner可以感知整个进程的生命周期,监控应用的前后台切换轻而易举.

使用ProcessLifecycleOwner可能需要在build.grade里添加依赖:

implementation "android.arch.lifecycle:extensions:1.1.1"
或者
implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0-rc03'

3.全局管理Activity

我们经常会有这样的功能,面试官也会问这样的问题,想关闭所有Activity应该怎么做?

利用Application.ActivityLifecycleCallbacks有全新的方式来实现了.

class MyActivityLifeCycleCallBack : Application.ActivityLifecycleCallbacks {companion object {val instance = MyActivityLifeCycleCallBack()}private val activityList: ArrayList<Activity> = ArrayList()override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {activityList.add(activity)println("onActivityCreated : ${activity.localClassName}")}override fun onActivityStarted(activity: Activity) {println("onActivityStarted : ${activity.localClassName}")}override fun onActivityResumed(activity: Activity) {println("onActivityResumed : ${activity.localClassName}")}override fun onActivityPaused(activity: Activity) {println("onActivityPaused : ${activity.localClassName}")}override fun onActivityDestroyed(activity: Activity) {println("onActivityDestroyed : ${activity.localClassName}")activityList.remove(activity)}override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle?) {}override fun onActivityStopped(activity: Activity) {println("onActivityStopped : ${activity.localClassName}")}fun clearAllActivity() {for (activity: Activity in activityList) {activity.finish()}}
}

通过Application.ActivityLifecycleCallbacks可以监听到所有Activity的生命周期,只要在Application中注册这个Callback就行了.

registerActivityLifecycleCallbacks(MyActivityLifeCycleCallBack.instance)

在这里插入图片描述

此时每个Activity的生命周期就都在我们的监控中了,如果我们想要实现关闭所有的Activity可以这样做:

在MyActivityLifecycleCallback我们实现了一个clearAllActivity的方法,很简单 , 并且将MyActivityLifecycleCallback做为一个单例使用.

companion object { 
val instance = MyActivityLifeCycleCallBack() 
} fun clearAllActivity() { 
for (activity: Activity in activityList) { 
activity.finish() 
} 
}