blocks|key|159006|text|关于第2)和第3)点，您可以执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|159007|159008|在您的服务的onCreate()方法中，生成一个随机数或时间戳并保存到本地字段；这将是服务ID+|unordered-list-item|offset|length|style|CODE|159009|在您的BroadcastReceiver中注册一个自定义BroadcastReceiver，它将在每个Service创建时响应您的自定义动作|159010|，发送带有您的自定义动作和您当前的Service+ID的广播作为额外参数|159011|对于每个活动的Service，将触发已注册的BroadcastReceiver；现在将收到的ID与当前服务的ID进行比较，如果不同，则调用stopSelf()|159012|+|159013|159014|159015|​|159016|这样，只有最后的Service才能存活下来。|159017|entityMap^0|0|0|6|A|0|3|H|S|H|1F|7|0|H|7|0|7|7|M|H|1X|A|0|0|0|0|0|8|7|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|10|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|11|8|@$F|12|G|13|H|I]]|9|@]|A|$]]|$1|J|3|K|5|E|7|14|8|@$F|15|G|16|H|I]|$F|17|G|18|H|I]|$F|19|G|1A|H|I]]|9|@]|A|$]]|$1|L|3|M|5|E|7|1B|8|@$F|1C|G|1D|H|I]]|9|@]|A|$]]|$1|N|3|O|5|E|7|1E|8|@$F|1F|G|1G|H|I]|$F|1H|G|1I|H|I]|$F|1J|G|1K|H|I]]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1L|8|@]|9|@]|A|$]]|$1|R|3|-4|5|E|7|1M|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1N|8|@]|9|@]|A|$]]|$1|T|3|U|5|6|7|1O|8|@]|9|@]|A|$]]|$1|V|3|W|5|6|7|1P|8|@$F|1Q|G|1R|H|I]]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1S|8|@]|9|@]|A|$]]]|Y|$]]

Regarding the points 2) and 3), you can do the following:

<ul>
<li>In your service's <code>onCreate()</code> method, generate a random number or a timestamp and save it to a local field; this will be the service ID</li>
<li>Register a custom <code>BroadcastReceiver</code> in your <code>Service</code>, it will
react to your custom ACTION</li>
<li>At each <code>Service</code> creation, send a broadcast with your custom ACTION and your current <code>Service</code> ID as extra param</li>
<li>For each active <code>Service</code>, the registered <code>BroadcastReceiver</code> will be triggered; now compare the received ID with the current service's ID

<ul>
<li>if they differ, invoke <code>stopSelf()</code></li>
</ul></li>
</ul>

In this way, only the last <code>Service</code> will stay alive.

blocks|key|161439|text|首先，在AOSP问题跟踪器上有一个open+issue+tracking+this+problem。提交bug的人可以在所有Android+4.x版本中重现，但没有在5.x版本中进行测试。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|161440|以下是术语的简要说明：|161441|161442|NsdManager+-+Android应用程序接口的类，用于注册其NSD服务和发现其他NSD服务。NsdManager实际上只是一个外壳，它与隐藏在NsdService.|unordered-list-item|style|BOLD|161443|NsdService(com.android.server.NsdService)中的安卓系统服务建立了异步连接，可以从多个客户端进行连接。完成创建和管理NSD服务以及将事件传回客户端applications.|161444|NSD服务的所有繁重工作和记账-+NsdService代表您创建的服务，用于通过网络通告您的应用程序的存在。|161445|161446|我刚刚用5.1测试了这个问题，这个问题已经修复了(从源代码上看，这个修复已经进入了5.0)。我创建了一个简单的应用程序，当发生任何值得注意的事件时，包括生命周期事件onCreate、onResume、onPause和onDestroy，它只注册一个NsdService并记录日志。通过重启，启动我的应用程序，然后通过Android+Studio重新安装，我得到了以下日志。|161447|W/SimpleNsdActivity(14379):+onCreate
D/NsdService(+3516):+startMDnsDaemon
D/NsdService(+3516):+New+client+listening+to+asynchronous+messages
D/NsdService(+3516):+New+client,+channel:+com.android.internal.util.AsyncChannel
@3c114a11+messenger:+android.os.Messenger@3213e776
D/NsdService(+3516):+Register+service
D/NsdService(+3516):+registerService:+2+name:+NsdTest,+type:+_http._tcp.,+host:
null,+port:+1349
W/SimpleNsdActivity(14379):+onResume
D/NsdService(+3516):+Register+1+2
W/SimpleNsdActivity(14379):+onServiceRegistered+as+NsdTest
D/NsdService(+3516):+SERVICE_REGISTERED+Raw:+606+2+"NsdTest"
D/NsdService(+3516):+Client+disconnected
D/NsdService(+3516):+Terminating+client-ID+1+global-ID+2+type+393225
D/NsdService(+3516):+unregisterService:+2
D/NsdService(+3516):+stopMDnsDaemon
W/SimpleNsdActivity(15729):+onCreate
D/NsdService(+3516):+startMDnsDaemon
D/NsdService(+3516):+New+client+listening+to+asynchronous+messages
D/NsdService(+3516):+New+client,+channel:+com.android.internal.util.AsyncChannel
@38bace07+messenger:+android.os.Messenger@26d8cd5d
D/NsdService(+3516):+Register+service
D/NsdService(+3516):+registerService:+3+name:+NsdTest,+type:+_http._tcp.,+host:
null,+port:+1349
D/NsdService(+3516):+Register+1+3
W/SimpleNsdActivity(15729):+onResume
D/NsdService(+3516):+SERVICE_REGISTERED+Raw:+606+3+"NsdTest"
W/SimpleNsdActivity(15729):+onServiceRegistered+as+NsdTest|code-block|syntax|javascript|161448|您可以看到，onPause()和onDestroy()都没有被调用，因此我的应用程序没有对NSD服务进行显式清理。NsdService正在检测到客户端的AsyncChannel何时终止，并正在正确地进行清理。通过查看源here，您可以更深入地了解NsdService日志。|CODE|161449|综上所述，我将回答提示符中的问题：|161450|161451|For+4.x没有超时，它将一直保持到重新启动。对于5.x，当你的应用程序disconnects.|ordered-list-item|161452|There不能保证调用onDestroy()时，NsdService会关闭NSD服务，更深层次的解释是here。通过Android+Studio安装，在不调用的情况下终止正在运行的应用程序。看看通过应用程序商店的更新是以同样的方式运行还是更优雅地关闭正在运行的应用程序会很有趣。|161453|在5.x中不是问题，因为它会立即杀死它们。在4.x中，没有办法删除旧的注册，因为您会立即失去注册侦听器。|161454|161455|entityMap|0|LINK|mutability|MUTABLE|url|https://code.google.com/p/android/issues/detail?id=82744&q=nsdmanager&colspec=ID%2520Type%2520Status%2520Owner%2520Summary%2520Stars#makechanges|1|http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/5.1.0_r1/com/android/server/NsdService.java#163|2|https://stackoverflow.com/questions/4449955/activity-ondestroy-never-called^0|H|W|0|0|0|0|0|A|0|0|A|0|0|5|0|0|0|0|6|9|G|B|31|4|1|0|0|0|0|1F|4|2|0|0|0^^$0|@$1|2|3|4|5|6|7|1N|8|@]|9|@$A|1O|B|1P|1|1Q]]|C|$]]|$1|D|3|E|5|6|7|1R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|1S|8|@]|9|@]|C|$]]|$1|G|3|H|5|I|7|1T|8|@$A|1U|B|1V|J|K]]|9|@]|C|$]]|$1|L|3|M|5|I|7|1W|8|@$A|1X|B|1Y|J|K]]|9|@]|C|$]]|$1|N|3|O|5|I|7|1Z|8|@$A|20|B|21|J|K]]|9|@]|C|$]]|$1|P|3|-4|5|6|7|22|8|@]|9|@]|C|$]]|$1|Q|3|R|5|6|7|23|8|@]|9|@]|C|$]]|$1|S|3|T|5|U|7|24|8|@]|9|@]|C|$V|W]]|$1|X|3|Y|5|6|7|25|8|@$A|26|B|27|J|Z]|$A|28|B|29|J|Z]]|9|@$A|2A|B|2B|1|2C]]|C|$]]|$1|10|3|11|5|6|7|2D|8|@]|9|@]|C|$]]|$1|12|3|-4|5|6|7|2E|8|@]|9|@]|C|$]]|$1|13|3|14|5|15|7|2F|8|@]|9|@]|C|$]]|$1|16|3|17|5|15|7|2G|8|@]|9|@$A|2H|B|2I|1|2J]]|C|$]]|$1|18|3|19|5|15|7|2K|8|@]|9|@]|C|$]]|$1|1A|3|-4|5|6|7|2L|8|@]|9|@]|C|$]]|$1|1B|3|-4|5|6|7|2M|8|@]|9|@]|C|$]]]|1C|$1D|$5|1E|1F|1G|C|$1H|1I]]|1J|$5|1E|1F|1G|C|$1H|1K]]|1L|$5|1E|1F|1G|C|$1H|1M]]]]

First of all, there is an <a href="https://code.google.com/p/android/issues/detail?id=82744&amp;q=nsdmanager&amp;colspec=ID%20Type%20Status%20Owner%20Summary%20Stars#makechanges" rel="nofollow noreferrer">open issue tracking this problem</a> on the AOSP issue tracker. The person who filed the bug could repro in all Android 4.x versions but did not test with 5.x. 

A brief explanation of terms:

<ul>
<li>NsdManager - the class that Android applications interface with to register their NSD service and discover other NSD services. NsdManager is really just a shell that establishes an asynchronous connection with NsdService.</li>
<li>NsdService(com.android.server.NsdService) - hidden Android system service that can have connections from multiple clients. Does all the heavy lifting and book-keeping for creating and managing NSD service and communicating events back to client applications.</li>
<li>NSD service - the service that NsdService creates on your behalf that advertises your app's presence over the network.</li>
</ul>

I just tested this issue with 5.1 and the issue is fixed(from the source it looks like the fix went into 5.0). I created a simple application that just registers an NsdService and logs when anything of note happens, including lifecycle events onCreate, onResume, onPause, and onDestroy. I got the following logs by rebooting, starting my application, and then reinstalling via Android Studio.

<pre><code>W/SimpleNsdActivity(14379): onCreate
D/NsdService( 3516): startMDnsDaemon
D/NsdService( 3516): New client listening to asynchronous messages
D/NsdService( 3516): New client, channel: com.android.internal.util.AsyncChannel
@3c114a11 messenger: android.os.Messenger@3213e776
D/NsdService( 3516): Register service
D/NsdService( 3516): registerService: 2 name: NsdTest, type: _http._tcp., host:
null, port: 1349
W/SimpleNsdActivity(14379): onResume
D/NsdService( 3516): Register 1 2
W/SimpleNsdActivity(14379): onServiceRegistered as NsdTest
D/NsdService( 3516): SERVICE_REGISTERED Raw: 606 2 "NsdTest"
D/NsdService( 3516): Client disconnected
D/NsdService( 3516): Terminating client-ID 1 global-ID 2 type 393225
D/NsdService( 3516): unregisterService: 2
D/NsdService( 3516): stopMDnsDaemon
W/SimpleNsdActivity(15729): onCreate
D/NsdService( 3516): startMDnsDaemon
D/NsdService( 3516): New client listening to asynchronous messages
D/NsdService( 3516): New client, channel: com.android.internal.util.AsyncChannel
@38bace07 messenger: android.os.Messenger@26d8cd5d
D/NsdService( 3516): Register service
D/NsdService( 3516): registerService: 3 name: NsdTest, type: _http._tcp., host:
null, port: 1349
D/NsdService( 3516): Register 1 3
W/SimpleNsdActivity(15729): onResume
D/NsdService( 3516): SERVICE_REGISTERED Raw: 606 3 "NsdTest"
W/SimpleNsdActivity(15729): onServiceRegistered as NsdTest
</code></pre>

You can see that neither <code>onPause()</code> nor <code>onDestroy()</code> were called and thus my application did no explicit cleanup for the NSD service. NsdService is detecting when the AsyncChannel to the client is terminated and is cleaning it up properly. You can get a deeper understanding of the NsdService logs by looking at the source <a href="http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/5.1.0_r1/com/android/server/NsdService.java#163" rel="nofollow noreferrer">here</a>.

Summing it all up, I'll respond to the questions from the prompt:

<ol>
<li>For 4.x there is no timeout, it will stay up until reboot. For 5.x NsdService shuts down the NSD service when your app disconnects.</li>
<li>There is no way to guarantee onDestroy() is called, a deeper explanation <a href="https://stackoverflow.com/questions/4449955/activity-ondestroy-never-called">here</a>. Installation via Android Studio killing the running application without it being called. Would be interesting to see if updates via the App Store behave the same way or more gracefully shut down the running app.</li>
<li>Not a problem in 5.x since it kills them right away. In 4.x, there's no way to remove old registrations since you immediately lose the registration listener.</li>
</ol>

I'm using Network Service Discover (NSD) on Android to advertise a REST server on the device. My REST server is wrapped in an instance of <a href="http://developer.android.com/reference/android/app/Service.html">android.app.Service</a>.

In the <code>onCreate</code>, I successfully start the REST server and register my NSD service. I can see the NSD service name on other devices within my network (e.g. My Service).

In my <code>onDestroy</code>, I stop the REST Server and unregister the NSD service.

However, it seems that while developing, when I push a new instance of my app (via Eclipse), there's no guarantee that the service's <code>onDestroy</code> will be called. This means that My Service is still advertised, and the next time the service starts, I end up with My Service (1), My Service (2), etc.

I understand that NSD will amend the service name to create a unique instance. My questions are:

<ol>
<li>What's the expected timeout for advertised services to be removed if they no longer exist?</li>
<li>Is there a way to ensure my <code>onDestroy</code> is being called when I push a new instance of my app? Would this circumstance be similar to what a user might experience if they install an update of my app? i.e. is the <code>onDestroy</code> guaranteed to be called when a running app is shutdown so a new version of that app can be installed?</li>
<li>Is there a way within my app to detect the old registrations and remove them?</li>
</ol>

Android Network Service Discovery "timeout"?

Android Studio

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Android

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我在Android上使用Network Service Discover (NSD)在设备上通告REST服务器。我的REST服务器包装在的一个实例中。在onCreate中，我成功地启动了REST服务器并注册了我的NSD服务。我可以在网络中的其他设备上看到NSD服务名称(例如，我的服务)。在我的onDestroy中，我停...

问Android网络服务发现“超时”？
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