blocks|key|164848|text|要做到这一点并不容易，但是有一些轻量级的库可以以一种简单的方式做你想要的事情。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|164849|我正在使用this+one，它工作得非常好。|offset|length|164850|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/jenzz/RxAppState^0|0|5|8|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

It's not easy to accomplish, but there are some lightweight libraries that do what you want in an easy way.

I am using <a href="https://github.com/jenzz/RxAppState" rel="nofollow noreferrer">this one</a>, it works really well.

blocks|key|3432953|text|您可以做的是在Application类中注册活动生命周期回调。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3432954|请参见：|3432955|https://developer.android.com/reference/android/app/Application.ActivityLifecycleCallbacks|3432956|https://developer.android.com/reference/android/app/Application#registerActivityLifecycleCallbacks(android.app.Application.ActivityLifecycleCallbacks)|3432957|然后，您可以简单地使用一个计数器，该计数器在活动开始时递增，在活动停止时递减。如果计数器的值为零，则当前在前台没有活动。|3432958|entityMap|0|LINK|mutability|MUTABLE|url|1^0|7|B|0|0|0|2I|0|0|0|46|1|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|Z|8|@]|D|@$9|10|A|11|1|12]]|E|$]]|$1|J|3|K|5|6|7|13|8|@]|D|@$9|14|A|15|1|16]]|E|$]]|$1|L|3|M|5|6|7|17|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|O|$P|$5|Q|R|S|E|$T|I]]|U|$5|Q|R|S|E|$T|K]]]]

What you can do is register for activity lifecycle callbacks in your <code>Application</code> class.

See:

<a href="https://developer.android.com/reference/android/app/Application.ActivityLifecycleCallbacks" rel="nofollow noreferrer">https://developer.android.com/reference/android/app/Application.ActivityLifecycleCallbacks</a>

<a href="https://developer.android.com/reference/android/app/Application#registerActivityLifecycleCallbacks(android.app.Application.ActivityLifecycleCallbacks)" rel="nofollow noreferrer">https://developer.android.com/reference/android/app/Application#registerActivityLifecycleCallbacks(android.app.Application.ActivityLifecycleCallbacks)</a>

You can then simply have a counter that increments when an activity starts and decrement it when an activity stops. If the value of the counter is zero then there are currently no activity in the foreground.

blocks|key|164909|text|Kotlin中的示例：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|164910|import+java.io.Closeable
import+kotlinx.coroutines.channels.Channel
import+kotlinx.coroutines.runBlocking
import+androidx.lifecycle.*

class+AppLifecycleService()+:+LifecycleObserver,+Closeable+{

++++val+channel+=+Channel<Boolean>()

++++init+{
++++++++ProcessLifecycleOwner.get().lifecycle.addObserver(this)
++++}

++++@OnLifecycleEvent(Lifecycle.Event.ON_START)
++++fun+onMoveToForeground()+{
++++++++runBlocking+{+channel.send(true)+}
++++}

++++@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
++++fun+onMoveToBackground()+{
++++++++runBlocking+{+channel.send(false)+}
++++}

++++override+fun+close()+{
++++++++ProcessLifecycleOwner.get().lifecycle.removeObserver(this)
++++++++channel.close()
++++}
}|code-block|syntax|javascript|164911|在某个地方实例化该类，并订阅通道。当你获得和失去焦点时，它会向你发送true/false。当你的应用完成后，close()这个类的引用。|offset|length|style|CODE|164912|entityMap^0|0|0|1I|7|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Example in Kotlin:

<pre><code>import java.io.Closeable
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.runBlocking
import androidx.lifecycle.*

class AppLifecycleService() : LifecycleObserver, Closeable {

 val channel = Channel&lt;Boolean&gt;()

 init {
 ProcessLifecycleOwner.get().lifecycle.addObserver(this)
 }

 @OnLifecycleEvent(Lifecycle.Event.ON_START)
 fun onMoveToForeground() {
 runBlocking { channel.send(true) }
 }

 @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
 fun onMoveToBackground() {
 runBlocking { channel.send(false) }
 }

 override fun close() {
 ProcessLifecycleOwner.get().lifecycle.removeObserver(this)
 channel.close()
 }
}
</code></pre>

Instantiate the class somewhere, and subscribe to the channel. It will send you true/false for when you gain and lose focus. When your app is done, <code>close()</code> the reference to this class.

I am new to coding and I was wondering, if there is a way to check when app loses focus(goes from foreground to background).

Is there anything like <code>onLosefocuslistener</code>?

To clarify I don't want when activity loses focus. I want when the whole app goes in background either cause user pressed the 'home' button or another app went in foreground.

How to check whether my app has lost focus?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我是编程新手，我想知道，是否有一种方法可以检查应用程序何时失去焦点(从前台到后台)。有没有像onLosefocuslistener这样的东西澄清一下，我不希望当活动失去焦点时。我希望当整个应用程序进入后台，要么是因为用户按下了“主页”按钮，要么是另一个应用程序进入了前台。

问如何检查我的应用是否失去了焦点？
EN

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问如何检查我的应用是否失去了焦点？EN