IntentService简介

小咪咪 2022-04-18 01:23 134阅读 0赞

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英文原文： [http://developer.android.com/reference/android/app/IntentService.html][http_developer.android.com_reference_android_app_IntentService.html]

参照文章： [http://android.tgbus.com/Android/tutorial/201106/355229.shtml][http_android.tgbus.com_Android_tutorial_201106_355229.shtml]

IntentService 是Service类的子类，用来处理异步请求。客户端可以通过startService(Intent)方法传递请求给 IntentService 。 IntentService 在 onCreate() 函数中通过 HandlerThread 单独开启一个线程来处理所有Intent请求对象（通过startService的方式发送过来的）所对应的任务，这样以免事务处理阻塞主线程。 执行完所一个Intent请求对象所对应的工作之后，如果没有新的Intent请求达到，则自动停止Service；否则执行下一个Intent请求所对应的任务。

IntentService在处理事务时，还是采用的Handler方式，创建一个名叫 ServiceHandler 的内部Handler，并把它直接绑定到 HandlerThread所对应的子线程。  ServiceHandler把处理 一个intent所对应的事务都封装到叫做 onHandleInten t的虚函数；因此我们直接实现 虚函数 onHandleIntent ，再在里面根据Intent的不同进行不同的事务处理就可以了。

另外， IntentService默认实现了Onbind（）方法，返回值为null。

使用IntentService需要两个步骤：

1 、写构造函数

2 、 实现 虚函数 onHandleIntent ，并在里面根据Intent的不同进行不同的事务处理就可以了。

好处：处理异步请求的时候可以减少写代码的工作量，比较轻松地实现项目的需求

**注意**： IntentService的构造函数一定是参数为空的构造函数，然后再在其中调用 super("name")这种形式的构造函数。

因为Service的实例化是系统来完成的，而且系统是用 参数为空的 构造函数来 实例化 Service的

关于Handler和Service的更多知识请阅读《 [Looper和Handler][Looper_Handler] 》，《 [关于Handler技术][Handler] 》，《 [Service简介][Service] 》，《 [AIDL和Service实现两进程通信][AIDL_Service] 》

<table> 
 <tbody> 
  <tr> 
   <th colspan="12">Public Constructors</th> 
  </tr> 
  <tr> 
   <td></td> 
   <td><a href="http://developer.android.com/reference/android/app/IntentService.html#IntentService%28java.lang.String%29" rel="nofollow">IntentService</a>(<a href="http://developer.android.com/reference/java/lang/String.html" rel="nofollow">String</a>&nbsp;name) 
    <div>
      Creates an IntentService. 
    </div></td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <th colspan="12">Public Methods</th> 
  </tr> 
  <tr> 
   <td><a href="http://developer.android.com/reference/android/os/IBinder.html" rel="nofollow">IBinder</a></td> 
   <td><a href="http://developer.android.com/reference/android/app/IntentService.html#onBind%28android.content.Intent%29" rel="nofollow">onBind</a>(<a href="http://developer.android.com/reference/android/content/Intent.html" rel="nofollow">Intent</a>&nbsp;intent) 
    <div>
      Unless you provide binding for your service, you don't need to implement this method, because the default implementation returns null. 
    </div></td> 
  </tr> 
  <tr> 
   <td>void</td> 
   <td><a href="http://developer.android.com/reference/android/app/IntentService.html#onCreate%28%29" rel="nofollow">onCreate</a>() 
    <div>
      Called by the system when the service is first created. 
    </div></td> 
  </tr> 
  <tr> 
   <td>void</td> 
   <td><a href="http://developer.android.com/reference/android/app/IntentService.html#onDestroy%28%29" rel="nofollow">onDestroy</a>() 
    <div>
      Called by the system to notify a Service that it is no longer used and is being removed. 
    </div></td> 
  </tr> 
  <tr> 
   <td>void</td> 
   <td><a href="http://developer.android.com/reference/android/app/IntentService.html#onStart%28android.content.Intent,%20int%29" rel="nofollow">onStart</a>(<a href="http://developer.android.com/reference/android/content/Intent.html" rel="nofollow">Intent</a>&nbsp;intent,&nbsp;int startId) 
    <div> 
     <em>This method is deprecated. Implement&nbsp;<code><a href="http://developer.android.com/reference/android/app/Service.html#onStartCommand%28android.content.Intent,%20int,%20int%29" rel="nofollow">onStartCommand(Intent,&nbsp;int, int)</a></code>&nbsp;instead.</em> 
    </div></td> 
  </tr> 
  <tr> 
   <td>int</td> 
   <td><a href="http://developer.android.com/reference/android/app/IntentService.html#onStartCommand%28android.content.Intent,%20int,%20int%29" rel="nofollow">onStartCommand</a>(<a href="http://developer.android.com/reference/android/content/Intent.html" rel="nofollow">Intent</a>&nbsp;intent,&nbsp;int flags, int startId) 
    <div>
      You should not override this method for your IntentService. 
    </div></td> 
  </tr> 
  <tr> 
   <td>void</td> 
   <td><a href="http://developer.android.com/reference/android/app/IntentService.html#setIntentRedelivery%28boolean%29" rel="nofollow">setIntentRedelivery</a>(boolean enabled) 
    <div>
      Sets intent redelivery preferences. 
    </div> 
    <div> 
     <p>If enabled is true,&nbsp;<code><a href="http://developer.android.com/reference/android/app/IntentService.html#onStartCommand%28android.content.Intent,%20int,%20int%29" rel="nofollow">onStartCommand(Intent,&nbsp;int, int)</a></code>&nbsp;will return&nbsp;<code><a href="http://developer.android.com/reference/android/app/Service.html#START_REDELIVER_INTENT" rel="nofollow">START_REDELIVER_INTENT</a></code>,&nbsp;so if this process dies before&nbsp;<code><a href="http://developer.android.com/reference/android/app/IntentService.html#onHandleIntent%28android.content.Intent%29" rel="nofollow">onHandleIntent(Intent)</a></code>returns,&nbsp;the process will be restarted and the intent redelivered. If multiple Intents have been sent, only the most recent one is guaranteed to be redelivered.</p> 
     <p>If enabled is false (the default),&nbsp;<code><a href="http://developer.android.com/reference/android/app/IntentService.html#onStartCommand%28android.content.Intent,%20int,%20int%29" rel="nofollow">onStartCommand(Intent,&nbsp;int, int)</a></code>&nbsp;will return&nbsp;<code><a href="http://developer.android.com/reference/android/app/Service.html#START_NOT_STICKY" rel="nofollow">START_NOT_STICKY</a></code>,&nbsp;and if the process dies, the Intent dies along with it.</p> 
    </div> 
    <div>
      设置为true时， 
     <a href="http://developer.android.com/reference/android/app/IntentService.html#onStartCommand%28android.content.Intent,%20int,%20int%29" rel="nofollow">onStartCommand</a> 返回 START_REDELIVER_INTENT，否则返回 START_NOT_STICKY 
    </div> 
    <div>
      关于此的更多内容请参考《 
     <a title="阅读全文" href="http://hubingforever.blog.163.com/blog/static/17104057920105158535757/" rel="nofollow">Service简介</a> 》 
    </div></td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <tbody> 
  <tr> 
   <th colspan="12">Protected Methods</th> 
  </tr> 
  <tr> 
   <td>abstract void</td> 
   <td><a href="http://developer.android.com/reference/android/app/IntentService.html#onHandleIntent%28android.content.Intent%29" rel="nofollow">onHandleIntent</a>(<a href="http://developer.android.com/reference/android/content/Intent.html" rel="nofollow">Intent</a>&nbsp;intent) 
    <div>
      This method is invoked on the worker thread with a request to process. 
    </div> 
    <div>
      This method is invoked on the worker thread with a request to process. Only one Intent is processed at a time, but the processing happens&nbsp;on a worker thread that runs independently from other application logic. So, if this code takes a long time, it will hold up other requests to the same IntentService, but it will not hold up anything else. When all requests have been handled, the IntentService&nbsp;stops itself, so you should not call&nbsp; 
     <code><a href="http://developer.android.com/reference/android/app/Service.html#stopSelf%28%29" rel="nofollow">stopSelf()</a></code> . 
    </div> 
    <div>
      该函数用于针对Intent的不同进行不同的事务处理就可以了.执行完所一个Intent请求对象所对应的工作之后，如果没有新的Intent请求达到， 
    </div> 
    <div>
      则自动停止Service；否则 ServiceHandler会取得 下一个Intent请求传人该函数来处理其所对应的任务。 
    </div> 
    <div> 
     <br> 
    </div></td> 
  </tr> 
 </tbody> 
</table>

**实例1**

MyIntentService.java文件

package  com . lenovo . robin . test ;

import  android . app . IntentService ;

import  android . content . Intent ;

import  android . util . Log ;

public  class  MyIntentService  extends  IntentService  \{

final  static  String  TAG = "robin" ;

public  MyIntentService ()  \{

super ( "com.lenovo.robin.test.MyIntentService" );

Log . i ( TAG , this \+ " is constructed" );

@Override

protected  void  onHandleIntent ( Intent  arg0 )  \{

Log . i ( TAG , "begin onHandleIntent() in " \+ this );

try  \{

Thread . sleep ( 10 \* 1000 );

\}  catch  ( InterruptedException  e )  \{

e . printStackTrace ();

Log . i ( TAG , "end onHandleIntent() in " \+ this );

public  void  onDestroy ()

super . onDestroy ();

Log . i ( TAG , this \+ " is destroy" );

启动 MyIntentServic的代码片段

Intent  intent = new  Intent ( this , MyIntentService . class );

startService ( intent );

AndroidManifest.xml文件代码片段

<serviceandroid:name=".MyIntentService"/>

运行结果

09-14 22:23:34.730: I/robin(30943): com.lenovo.robin.test.MyIntentService@40541370 is  constructed

09-14 22:23:34.730: I/robin(30943):  begin  onHandleIntent() in com.lenovo.robin.test.MyIntentService@ 40541370

09-14 22:23:44.730: I/robin(30943):  end  onHandleIntent() in com.lenovo.robin.test.MyIntentService@ 40541370

09-14 22:23:44.730: I/robin(30943):  begin  onHandleIntent() in com.lenovo.robin.test.MyIntentService@ 40541370

09-14 22:23:54.740: I/robin(30943):  end  onHandleIntent() in com.lenovo.robin.test.MyIntentService@ 40541370

09-14 22:23:54.740: I/robin(30943):  begin  onHandleIntent() in com.lenovo.robin.test.MyIntentService@ 40541370

09-14 22:24:04.739: I/robin(30943):  end  onHandleIntent() in com.lenovo.robin.test.MyIntentService@ 40541370

09-14 22:24:04.739: I/robin(30943): com.lenovo.robin.test.MyIntentService@40541370 is  destroy

IntentService源码

package  android . app ;

import  android . content . Intent ;

import  android . os . Handler ;

import  android . os . HandlerThread ;

import  android . os . IBinder ;

import  android . os . Looper ;

import  android . os . Message ;

public  abstract  class  IntentService  extends  Service  \{

private  volatile  Looper  mServiceLooper ;

private  volatile  ServiceHandler  mServiceHandler ;

private  String  mName ;

private  boolean  mRedelivery ;

private  final  class  ServiceHandler  extends  Handler  \{

public  ServiceHandler ( Looper  looper )  \{

super ( looper );

@Override

public  void  handleMessage ( Message  msg )  \{

onHandleIntent (( Intent ) msg . obj );

stopSelf ( msg . arg1 );

public  IntentService ( String  name )  \{

super ();

mName  =  name ;

public  void  setIntentRedelivery ( boolean  enabled )  \{

mRedelivery  =  enabled ;

@Override

public  void  onCreate ()  \{

// TODO: It would be nice to have an option to hold a partial wakelock

// during processing, and to have a static startService(Context, Intent)

// method that would launch the service & hand off a wakelock.

super . onCreate ();

HandlerThread  thread  =  new  HandlerThread ( "IntentService\["  \+  mName  \+  "\]" );

thread . start ();

mServiceLooper  =  thread . getLooper ();

mServiceHandler  =  new  ServiceHandler ( mServiceLooper );

@Override

public  void  onStart ( Intent  intent ,  int  startId )  \{

Message  msg  =  mServiceHandler . obtainMessage ();

msg . arg1  =  startId ;

msg . obj  =  intent ;

mServiceHandler . sendMessage ( msg );

/\*\*

\* You should not override this method for your IntentService. Instead,

\* override \{@link \#onHandleIntent\}, which the system calls when the IntentService

\* receives a start request.

\* @see android.app.Service\#onStartCommand

\*/

@Override

public  int  onStartCommand ( Intent  intent ,  int  flags ,  int  startId )  \{

onStart ( intent ,  startId );

return  mRedelivery  ?  START\_REDELIVER\_INTENT  :  START\_NOT\_STICKY ;

@Override

public  void  onDestroy ()  \{

mServiceLooper . quit ();

@Override

public  IBinder  onBind ( Intent  intent )  \{

return  null ;

protected  abstract  void  onHandleIntent ( Intent  intent );

结束！

#### 给我老师的人工智能教程打call！[http://blog.csdn.net/jiangjunshow][http_blog.csdn.net_jiangjunshow] ####

![这里写图片描述][SouthEast]

[http_blog.csdn.net_jiangjunshow]: https://blog.csdn.net/jiangjunshow/article/details/77338485
[http_developer.android.com_reference_android_app_IntentService.html]: http://developer.android.com/reference/android/app/IntentService.html
[http_android.tgbus.com_Android_tutorial_201106_355229.shtml]: http://android.tgbus.com/Android/tutorial/201106/355229.shtml
[Looper_Handler]: http://hubingforever.blog.163.com/blog/static/171040579201162034730266/
[Handler]: http://hubingforever.blog.163.com/blog/static/171040579201042587408/
[Service]: http://hubingforever.blog.163.com/blog/static/17104057920105158535757/
[AIDL_Service]: http://hubingforever.blog.163.com/blog/static/17104057920105158048283/
[SouthEast]: /images/20220418/c5e2c4558f9e4d3385203a0ccb3742c8.png