还是service
Service
extends?ContextWrapperimplements?ComponentCallbacks2
| java.lang.Object | |||
| ???? | android.content.Context | ||
| ? | ???? | android.content.ContextWrapper | |
| ? | ? | ???? | android.app.Service |
| Known Direct Subclasses AbstractInputMethodService,?AccessibilityService,?DreamService,?IntentService,?RecognitionService,?RemoteViewsService,?SpellCheckerService,?TextToSpeechService,VpnService,?WallpaperService |
| Known Indirect Subclasses InputMethodService |
Class Overview
A Service is an application component representing either an application's desire to perform a longer-running operation while not interacting with the user or to supply functionality for other applications to use. Each service class must have a corresponding?<service>?declaration in its package's?AndroidManifest.xml. Services can be started with?Context.startService()?and?Context.bindService().
service是一個應用程序組件它可以提供給屬于自己的進程內的其他組件執行長時間的阻塞操作也可以供其他進程使用（本地使用或者遠程使用），使用service需要在AndroidManifest.xml 里邊聲明。
有倆種方式啟動service 分別是Context.startService()?and?Context.bindService().
Note that services, like other application objects, run in the main thread of their hosting process. This means that, if your service is going to do any CPU intensive (such as MP3 playback) or blocking (such as networking) operations, it should spawn its own thread in which to do that work. More information on this can be found in?Processes and Threads. The?IntentService?class is available as a standard implementation of Service that has its own thread where it schedules its work to be done.
注意 service就像應用程序的其他組件 運行在宿主進程的主線程（UI）內。下邊的不說了 之前的翻譯已經介紹過了。
Topics covered here:
Developer Guides
For a detailed discussion about how to create services, read the?Services?developer guide.
What is a Service?
Most confusion about the Service class actually revolves around what it is?not:
- A Service is?not?a separate process. The Service object itself does not imply it is running in its own process; unless otherwise specified, it runs in the same process as the application it is part of. service不是一個單獨的進程 service自己滅有指明自己運行在自己的進程除非特別指明，它運行在同一進程中作為應用程序的一部分,
- A Service is?not?a thread. It is not a means itself to do work off of the main thread (to avoid Application Not Responding errors).
- service也不是一個線程 service不意味著自己脫離于主線程工作。主線程也叫做UI線程 安卓這么設計是為了避免應用程序沒有響應的錯誤而設計的。
Thus a Service itself is actually very simple, providing two main features: service 非常簡單 主要提供倆個主要功能特性。
- A facility for the application to tell the system?about?something it wants to be doing in the background (even when the user is not directly interacting with the application). This corresponds to calls to?Context.startService(), which ask the system to schedule work for the service, to be run until the service or someone else explicitly stop it.
- 作為應用程序的一個功能 請求系統“我”（這個service）想在后臺（用戶看不到它甚至滅有一點交互）做點服務本地客戶或者遠程客戶的事情。調用Context.startService()會請求 系統給這個service分配工作（翻譯的好別扭啊）這個service會一直運行下去直到它自己調用stopSelf（）或者其他組件停掉它。
- A facility for an application to expose some of its functionality to other applications. This corresponds to calls to?Context.bindService(), which allows a long-standing connection to be made to the service in order to interact with it.
- 給其他應用程序提供服務。需要調用Context.bindService()使用綁定方式啟動一個service 組件與被綁定的service的連接會一直保持并能交互。
When a Service component is actually created, for either of these reasons, all that the system actually does is instantiate the component and call its?onCreate()?and any other appropriate callbacks on the main thread. It is up to the Service to implement these with the appropriate behavior, such as creating a secondary thread in which it does its work.
當一個service被創建后
Note that because Service itself is so simple, you can make your interaction with it as simple or complicated as you want: from treating it as a local Java object that you make direct method calls on (as illustrated by?Local Service Sample), to providing a full remoteable interface using AIDL.
Service Lifecycle
There are two reasons that a service can be run by the system. If someone calls?Context.startService()?then the system will retrieve the service (creating it and calling its?onCreate()?method if needed) and then call its?onStartCommand(Intent, int, int)?method with the arguments supplied by the client. The service will at this point continue running until?Context.stopService()?or?stopSelf()?is called. Note that multiple calls to Context.startService() do not nest (though they do result in multiple corresponding calls to onStartCommand()), so no matter how many times it is started a service will be stopped once Context.stopService() or stopSelf() is called; however, services can use their?stopSelf(int)?method to ensure the service is not stopped until started intents have been processed.
For started services, there are two additional major modes of operation they can decide to run in, depending on the value they return from onStartCommand():START_STICKY?is used for services that are explicitly started and stopped as needed, while?START_NOT_STICKY?or?START_REDELIVER_INTENT?are used for services that should only remain running while processing any commands sent to them. See the linked documentation for more detail on the semantics.
Clients can also use?Context.bindService()?to obtain a persistent connection to a service. This likewise creates the service if it is not already running (callingonCreate()?while doing so), but does not call onStartCommand(). The client will receive the?IBinder?object that the service returns from its?onBind(Intent)?method, allowing the client to then make calls back to the service. The service will remain running as long as the connection is established (whether or not the client retains a reference on the service's IBinder). Usually the IBinder returned is for a complex interface that has been?written in aidl.
A service can be both started and have connections bound to it. In such a case, the system will keep the service running as long as either it is started?or?there are one or more connections to it with the?Context.BIND_AUTO_CREATE?flag. Once neither of these situations hold, the service's?onDestroy()?method is called and the service is effectively terminated. All cleanup (stopping threads, unregistering receivers) should be complete upon returning from onDestroy().
Permissions
Global access to a service can be enforced when it is declared in its manifest's?<service>?tag. By doing so, other applications will need to declare a corresponding<uses-permission>?element in their own manifest to be able to start, stop, or bind to the service.
As of?GINGERBREAD, when using?Context.startService(Intent), you can also set?Intent.FLAG_GRANT_READ_URI_PERMISSION?and/orIntent.FLAG_GRANT_WRITE_URI_PERMISSION?on the Intent. This will grant the Service temporary access to the specific URIs in the Intent. Access will remain until the Service has called?stopSelf(int)?for that start command or a later one, or until the Service has been completely stopped. This works for granting access to the other apps that have not requested the permission protecting the Service, or even when the Service is not exported at all.
In addition, a service can protect individual IPC calls into it with permissions, by calling the?checkCallingPermission(String)?method before executing the implementation of that call.
See the?Security and Permissions?document for more information on permissions and security in general.
Process Lifecycle
The Android system will attempt to keep the process hosting a service around as long as the service has been started or has clients bound to it. When running low on memory and needing to kill existing processes, the priority of a process hosting the service will be the higher of the following possibilities:
-
If the service is currently executing code in its?onCreate(),?onStartCommand(), or?onDestroy()?methods, then the hosting process will be a foreground process to ensure this code can execute without being killed.
-
If the service has been started, then its hosting process is considered to be less important than any processes that are currently visible to the user on-screen, but more important than any process not visible. Because only a few processes are generally visible to the user, this means that the service should not be killed except in extreme low memory conditions.
-
If there are clients bound to the service, then the service's hosting process is never less important than the most important client. That is, if one of its clients is visible to the user, then the service itself is considered to be visible.
-
A started service can use the?startForeground(int, Notification)?API to put the service in a foreground state, where the system considers it to be something the user is actively aware of and thus not a candidate for killing when low on memory. (It is still theoretically possible for the service to be killed under extreme memory pressure from the current foreground application, but in practice this should not be a concern.)
Note this means that most of the time your service is running, it may be killed by the system if it is under heavy memory pressure. If this happens, the system will later try to restart the service. An important consequence of this is that if you implement?onStartCommand()?to schedule work to be done asynchronously or in another thread, then you may want to use?START_FLAG_REDELIVERY?to have the system re-deliver an Intent for you so that it does not get lost if your service is killed while processing it.
Other application components running in the same process as the service (such as an?Activity) can, of course, increase the importance of the overall process beyond just the importance of the service itself.
Local Service Sample
One of the most common uses of a Service is as a secondary component running alongside other parts of an application, in the same process as the rest of the components. All components of an .apk run in the same process unless explicitly stated otherwise, so this is a typical situation.
When used in this way, by assuming the components are in the same process, you can greatly simplify the interaction between them: clients of the service can simply cast the IBinder they receive from it to a concrete class published by the service.
An example of this use of a Service is shown here. First is the Service itself, publishing a custom class when bound:
publicclassLocalServiceextendsService{? ? privateNotificationManager mNM;
? ? // Unique Identification Number for the Notification.
? ? // We use it on Notification start, and to cancel it.
? ? privateint NOTIFICATION = R.string.local_service_started;
? ? /**
? ? ?* Class for clients to access. ?Because we know this service always
? ? ?* runs in the same process as its clients, we don't need to deal with
? ? ?* IPC.
? ? ?*/
? ? publicclassLocalBinderextendsBinder{
? ? ? ? LocalService getService(){
? ? ? ? ? ? returnLocalService.this;
? ? ? ? }
? ? }
? ? @Override
? ? publicvoid onCreate(){
? ? ? ? mNM =(NotificationManager)getSystemService(NOTIFICATION_SERVICE);
? ? ? ? // Display a notification about us starting. ?We put an icon in the status bar.
? ? ? ? showNotification();
? ? }
? ? @Override
? ? publicint onStartCommand(Intent intent,int flags,int startId){
? ? ? ? Log.i("LocalService","Received start id "+ startId +": "+ intent);
? ? ? ? // We want this service to continue running until it is explicitly
? ? ? ? // stopped, so return sticky.
? ? ? ? return START_STICKY;
? ? }
? ? @Override
? ? publicvoid onDestroy(){
? ? ? ? // Cancel the persistent notification.
? ? ? ? mNM.cancel(NOTIFICATION);
? ? ? ? // Tell the user we stopped.
? ? ? ? Toast.makeText(this, R.string.local_service_stopped,Toast.LENGTH_SHORT).show();
? ? }
? ? @Override
? ? publicIBinder onBind(Intent intent){
? ? ? ? return mBinder;
? ? }
? ? // This is the object that receives interactions from clients. ?See
? ? // RemoteService for a more complete example.
? ? privatefinalIBinder mBinder =newLocalBinder();
? ? /**
? ? ?* Show a notification while this service is running.
? ? ?*/
? ? privatevoid showNotification(){
? ? ? ? // In this sample, we'll use the same text for the ticker and the expanded notification
? ? ? ? CharSequence text = getText(R.string.local_service_started);
? ? ? ? // Set the icon, scrolling text and timestamp
? ? ? ? Notification notification =newNotification(R.drawable.stat_sample, text,
? ? ? ? ? ? ? ? System.currentTimeMillis());
? ? ? ? // The PendingIntent to launch our activity if the user selects this notification
? ? ? ? PendingIntent contentIntent =PendingIntent.getActivity(this,0,
? ? ? ? ? ? ? ? newIntent(this,LocalServiceActivities.Controller.class),0);
? ? ? ? // Set the info for the views that show in the notification panel.
? ? ? ? notification.setLatestEventInfo(this, getText(R.string.local_service_label),
? ? ? ? ? ? ? ? ? ? ? ?text, contentIntent);
? ? ? ? // Send the notification.
? ? ? ? mNM.notify(NOTIFICATION, notification);
? ? }
}
With that done, one can now write client code that directly accesses the running service, such as:
privateLocalService mBoundService;privateServiceConnection mConnection =newServiceConnection(){
? ? publicvoid onServiceConnected(ComponentName className,IBinder service){
? ? ? ? // This is called when the connection with the service has been
? ? ? ? // established, giving us the service object we can use to
? ? ? ? // interact with the service. ?Because we have bound to a explicit
? ? ? ? // service that we know is running in our own process, we can
? ? ? ? // cast its IBinder to a concrete class and directly access it.
? ? ? ? mBoundService =((LocalService.LocalBinder)service).getService();
? ? ? ? // Tell the user about this for our demo.
? ? ? ? Toast.makeText(Binding.this, R.string.local_service_connected,
? ? ? ? ? ? ? ? Toast.LENGTH_SHORT).show();
? ? }
? ? publicvoid onServiceDisconnected(ComponentName className){
? ? ? ? // This is called when the connection with the service has been
? ? ? ? // unexpectedly disconnected -- that is, its process crashed.
? ? ? ? // Because it is running in our same process, we should never
? ? ? ? // see this happen.
? ? ? ? mBoundService =null;
? ? ? ? Toast.makeText(Binding.this, R.string.local_service_disconnected,
? ? ? ? ? ? ? ? Toast.LENGTH_SHORT).show();
? ? }
};
void doBindService(){
? ? // Establish a connection with the service. ?We use an explicit
? ? // class name because we want a specific service implementation that
? ? // we know will be running in our own process (and thus won't be
? ? // supporting component replacement by other applications).
? ? bindService(newIntent(Binding.this,
? ? ? ? ? ? LocalService.class), mConnection,Context.BIND_AUTO_CREATE);
? ? mIsBound =true;
}
void doUnbindService(){
? ? if(mIsBound){
? ? ? ? // Detach our existing connection.
? ? ? ? unbindService(mConnection);
? ? ? ? mIsBound =false;
? ? }
}
@Override
protectedvoid onDestroy(){
? ? super.onDestroy();
? ? doUnbindService();
}
Remote Messenger Service Sample
If you need to be able to write a Service that can perform complicated communication with clients in remote processes (beyond simply the use ofContext.startService?to send commands to it), then you can use the?Messenger?class instead of writing full AIDL files.
An example of a Service that uses Messenger as its client interface is shown here. First is the Service itself, publishing a Messenger to an internal Handler when bound:
publicclassMessengerServiceextendsService{? ? /** For showing and hiding our notification. */
? ? NotificationManager mNM;
? ? /** Keeps track of all current registered clients. */
? ? ArrayList<Messenger> mClients =newArrayList<Messenger>();
? ? /** Holds last value set by a client. */
? ? int mValue =0;
? ? /**
? ? ?* Command to the service to register a client, receiving callbacks
? ? ?* from the service. ?The Message's replyTo field must be a Messenger of
? ? ?* the client where callbacks should be sent.
? ? ?*/
? ? staticfinalint MSG_REGISTER_CLIENT =1;
? ? /**
? ? ?* Command to the service to unregister a client, ot stop receiving callbacks
? ? ?* from the service. ?The Message's replyTo field must be a Messenger of
? ? ?* the client as previously given with MSG_REGISTER_CLIENT.
? ? ?*/
? ? staticfinalint MSG_UNREGISTER_CLIENT =2;
? ? /**
? ? ?* Command to service to set a new value. ?This can be sent to the
? ? ?* service to supply a new value, and will be sent by the service to
? ? ?* any registered clients with the new value.
? ? ?*/
? ? staticfinalint MSG_SET_VALUE =3;
? ? /**
? ? ?* Handler of incoming messages from clients.
? ? ?*/
? ? classIncomingHandlerextendsHandler{
? ? ? ? @Override
? ? ? ? publicvoid handleMessage(Message msg){
? ? ? ? ? ? switch(msg.what){
? ? ? ? ? ? ? ? case MSG_REGISTER_CLIENT:
? ? ? ? ? ? ? ? ? ? mClients.add(msg.replyTo);
? ? ? ? ? ? ? ? ? ? break;
? ? ? ? ? ? ? ? case MSG_UNREGISTER_CLIENT:
? ? ? ? ? ? ? ? ? ? mClients.remove(msg.replyTo);
? ? ? ? ? ? ? ? ? ? break;
? ? ? ? ? ? ? ? case MSG_SET_VALUE:
? ? ? ? ? ? ? ? ? ? mValue = msg.arg1;
? ? ? ? ? ? ? ? ? ? for(int i=mClients.size()-1; i>=0; i--){
? ? ? ? ? ? ? ? ? ? ? ? try{
? ? ? ? ? ? ? ? ? ? ? ? ? ? mClients.get(i).send(Message.obtain(null,
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? MSG_SET_VALUE, mValue,0));
? ? ? ? ? ? ? ? ? ? ? ? }catch(RemoteException e){
? ? ? ? ? ? ? ? ? ? ? ? ? ? // The client is dead. ?Remove it from the list;
? ? ? ? ? ? ? ? ? ? ? ? ? ? // we are going through the list from back to front
? ? ? ? ? ? ? ? ? ? ? ? ? ? // so this is safe to do inside the loop.
? ? ? ? ? ? ? ? ? ? ? ? ? ? mClients.remove(i);
? ? ? ? ? ? ? ? ? ? ? ? }
? ? ? ? ? ? ? ? ? ? }
? ? ? ? ? ? ? ? ? ? break;
? ? ? ? ? ? ? ? default:
? ? ? ? ? ? ? ? ? ? super.handleMessage(msg);
? ? ? ? ? ? }
? ? ? ? }
? ? }
? ? /**
? ? ?* Target we publish for clients to send messages to IncomingHandler.
? ? ?*/
? ? finalMessenger mMessenger =newMessenger(newIncomingHandler());
? ? @Override
? ? publicvoid onCreate(){
? ? ? ? mNM =(NotificationManager)getSystemService(NOTIFICATION_SERVICE);
? ? ? ? // Display a notification about us starting.
? ? ? ? showNotification();
? ? }
? ? @Override
? ? publicvoid onDestroy(){
? ? ? ? // Cancel the persistent notification.
? ? ? ? mNM.cancel(R.string.remote_service_started);
? ? ? ? // Tell the user we stopped.
? ? ? ? Toast.makeText(this, R.string.remote_service_stopped,Toast.LENGTH_SHORT).show();
? ? }
? ? /**
? ? ?* When binding to the service, we return an interface to our messenger
? ? ?* for sending messages to the service.
? ? ?*/
? ? @Override
? ? publicIBinder onBind(Intent intent){
? ? ? ? return mMessenger.getBinder();
? ? }
? ? /**
? ? ?* Show a notification while this service is running.
? ? ?*/
? ? privatevoid showNotification(){
? ? ? ? // In this sample, we'll use the same text for the ticker and the expanded notification
? ? ? ? CharSequence text = getText(R.string.remote_service_started);
? ? ? ? // Set the icon, scrolling text and timestamp
? ? ? ? Notification notification =newNotification(R.drawable.stat_sample, text,
? ? ? ? ? ? ? ? System.currentTimeMillis());
? ? ? ? // The PendingIntent to launch our activity if the user selects this notification
? ? ? ? PendingIntent contentIntent =PendingIntent.getActivity(this,0,
? ? ? ? ? ? ? ? newIntent(this,Controller.class),0);
? ? ? ? // Set the info for the views that show in the notification panel.
? ? ? ? notification.setLatestEventInfo(this, getText(R.string.remote_service_label),
? ? ? ? ? ? ? ? ? ? ? ?text, contentIntent);
? ? ? ? // Send the notification.
? ? ? ? // We use a string id because it is a unique number. ?We use it later to cancel.
? ? ? ? mNM.notify(R.string.remote_service_started, notification);
? ? }
}
If we want to make this service run in a remote process (instead of the standard one for its .apk), we can use?android:process?in its manifest tag to specify one:
<serviceandroid:name=".app.MessengerService"? ? ? ? android:process=":remote"/>
Note that the name "remote" chosen here is arbitrary, and you can use other names if you want additional processes. The ':' prefix appends the name to your package's standard process name.
With that done, clients can now bind to the service and send messages to it. Note that this allows clients to register with it to receive messages back as well:
/** Messenger for communicating with service. */Messenger mService =null;
/** Flag indicating whether we have called bind on the service. */
boolean mIsBound;
/** Some text view we are using to show state information. */
TextView mCallbackText;
/**
?* Handler of incoming messages from service.
?*/
classIncomingHandlerextendsHandler{
? ? @Override
? ? publicvoid handleMessage(Message msg){
? ? ? ? switch(msg.what){
? ? ? ? ? ? caseMessengerService.MSG_SET_VALUE:
? ? ? ? ? ? ? ? mCallbackText.setText("Received from service: "+ msg.arg1);
? ? ? ? ? ? ? ? break;
? ? ? ? ? ? default:
? ? ? ? ? ? ? ? super.handleMessage(msg);
? ? ? ? }
? ? }
}
/**
?* Target we publish for clients to send messages to IncomingHandler.
?*/
finalMessenger mMessenger =newMessenger(newIncomingHandler());
/**
?* Class for interacting with the main interface of the service.
?*/
privateServiceConnection mConnection =newServiceConnection(){
? ? publicvoid onServiceConnected(ComponentName className,
? ? ? ? ? ? IBinder service){
? ? ? ? // This is called when the connection with the service has been
? ? ? ? // established, giving us the service object we can use to
? ? ? ? // interact with the service. ?We are communicating with our
? ? ? ? // service through an IDL interface, so get a client-side
? ? ? ? // representation of that from the raw service object.
? ? ? ? mService =newMessenger(service);
? ? ? ? mCallbackText.setText("Attached.");
? ? ? ? // We want to monitor the service for as long as we are
? ? ? ? // connected to it.
? ? ? ? try{
? ? ? ? ? ? Message msg =Message.obtain(null,
? ? ? ? ? ? ? ? ? ? MessengerService.MSG_REGISTER_CLIENT);
? ? ? ? ? ? msg.replyTo = mMessenger;
? ? ? ? ? ? mService.send(msg);
? ? ? ? ? ? // Give it some value as an example.
? ? ? ? ? ? msg =Message.obtain(null,
? ? ? ? ? ? ? ? ? ? MessengerService.MSG_SET_VALUE,this.hashCode(),0);
? ? ? ? ? ? mService.send(msg);
? ? ? ? }catch(RemoteException e){
? ? ? ? ? ? // In this case the service has crashed before we could even
? ? ? ? ? ? // do anything with it; we can count on soon being
? ? ? ? ? ? // disconnected (and then reconnected if it can be restarted)
? ? ? ? ? ? // so there is no need to do anything here.
? ? ? ? }
? ? ? ? // As part of the sample, tell the user what happened.
? ? ? ? Toast.makeText(Binding.this, R.string.remote_service_connected,
? ? ? ? ? ? ? ? Toast.LENGTH_SHORT).show();
? ? }
? ? publicvoid onServiceDisconnected(ComponentName className){
? ? ? ? // This is called when the connection with the service has been
? ? ? ? // unexpectedly disconnected -- that is, its process crashed.
? ? ? ? mService =null;
? ? ? ? mCallbackText.setText("Disconnected.");
? ? ? ? // As part of the sample, tell the user what happened.
? ? ? ? Toast.makeText(Binding.this, R.string.remote_service_disconnected,
? ? ? ? ? ? ? ? Toast.LENGTH_SHORT).show();
? ? }
};
void doBindService(){
? ? // Establish a connection with the service. ?We use an explicit
? ? // class name because there is no reason to be able to let other
? ? // applications replace our component.
? ? bindService(newIntent(Binding.this,
? ? ? ? ? ? MessengerService.class), mConnection,Context.BIND_AUTO_CREATE);
? ? mIsBound =true;
? ? mCallbackText.setText("Binding.");
}
void doUnbindService(){
? ? if(mIsBound){
? ? ? ? // If we have received the service, and hence registered with
? ? ? ? // it, then now is the time to unregister.
? ? ? ? if(mService !=null){
? ? ? ? ? ? try{
? ? ? ? ? ? ? ? Message msg =Message.obtain(null,
? ? ? ? ? ? ? ? ? ? ? ? MessengerService.MSG_UNREGISTER_CLIENT);
? ? ? ? ? ? ? ? msg.replyTo = mMessenger;
? ? ? ? ? ? ? ? mService.send(msg);
? ? ? ? ? ? }catch(RemoteException e){
? ? ? ? ? ? ? ? // There is nothing special we need to do if the service
? ? ? ? ? ? ? ? // has crashed.
? ? ? ? ? ? }
? ? ? ? }
? ? ? ? // Detach our existing connection.
? ? ? ? unbindService(mConnection);
? ? ? ? mIsBound =false;
? ? ? ? mCallbackText.setText("Unbinding.");
? ? }
}
?
Summary
| int | START_CONTINUATION_MASK | Bits returned by?onStartCommand(Intent, int, int)?describing how to continue the service if it is killed. |
| int | START_FLAG_REDELIVERY | This flag is set in?onStartCommand(Intent, int, int)?if the Intent is a re-delivery of a previously delivered intent, because the service had previously returned?START_REDELIVER_INTENT?but had been killed before callingstopSelf(int)?for that Intent. |
| int | START_FLAG_RETRY | This flag is set in?onStartCommand(Intent, int, int)?if the Intent is a a retry because the original attempt never got to or returned from?onStartCommand(Intent, int, int). |
| int | START_NOT_STICKY | Constant to return from?onStartCommand(Intent, int, int): if this service's process is killed while it is started (after returning from?onStartCommand(Intent, int, int)), and there are no new start intents to deliver to it, then take the service out of the started state and don't recreate until a future explicit call toContext.startService(Intent). |
| int | START_REDELIVER_INTENT | Constant to return from?onStartCommand(Intent, int, int): if this service's process is killed while it is started (after returning from?onStartCommand(Intent, int, int)), then it will be scheduled for a restart and the last delivered Intent re-delivered to it again via?onStartCommand(Intent, int, int). |
| int | START_STICKY | Constant to return from?onStartCommand(Intent, int, int): if this service's process is killed while it is started (after returning from?onStartCommand(Intent, int, int)), then leave it in the started state but don't retain this delivered intent. |
| int | START_STICKY_COMPATIBILITY | Constant to return from?onStartCommand(Intent, int, int): compatibility version of?START_STICKY?that does not guarantee that?onStartCommand(Intent, int, int)?will be called again after being killed. |
| From class?android.content.Context | |||||||||||
| From interface?android.content.ComponentCallbacks2 |
| ? | Service() |
| final?Application | getApplication() Return the application that owns this service. |
| abstract?IBinder | onBind(Intent?intent) Return the communication channel to the service. |
| void | onConfigurationChanged(Configuration?newConfig) Called by the system when the device configuration changes while your component is running. |
| void | onCreate() Called by the system when the service is first created. |
| void | onDestroy() Called by the system to notify a Service that it is no longer used and is being removed. |
| void | onLowMemory() This is called when the overall system is running low on memory, and would like actively running process to try to tighten their belt. |
| void | onRebind(Intent?intent) Called when new clients have connected to the service, after it had previously been notified that all had disconnected in itsonUnbind(Intent). |
| void | onStart(Intent?intent, int startId) This method was deprecated in API level 5. Implement?onStartCommand(Intent, int, int)?instead. |
| int | onStartCommand(Intent?intent, int flags, int startId) Called by the system every time a client explicitly starts the service by calling?startService(Intent), providing the arguments it supplied and a unique integer token representing the start request. |
| void | onTaskRemoved(Intent?rootIntent) This is called if the service is currently running and the user has removed a task that comes from the service's application. |
| void | onTrimMemory(int level) Called when the operating system has determined that it is a good time for a process to trim unneeded memory from its process. |
| boolean | onUnbind(Intent?intent) Called when all clients have disconnected from a particular interface published by the service. |
| final void | startForeground(int id,?Notification?notification) Make this service run in the foreground, supplying the ongoing notification to be shown to the user while in this state. |
| final void | stopForeground(boolean removeNotification) Remove this service from foreground state, allowing it to be killed if more memory is needed. |
| final void | stopSelf() Stop the service, if it was previously started. |
| final void | stopSelf(int startId) Old version of?stopSelfResult(int)?that doesn't return a result. |
| final boolean | stopSelfResult(int startId) Stop the service if the most recent time it was started was?startId. |
| void | dump(FileDescriptor?fd,?PrintWriter?writer,?String[]?args) Print the Service's state into the given stream. |
| ?From class?android.content.ContextWrapper | |||||||||||
| ?From class?android.content.Context | |||||||||||
| ?From class?java.lang.Object | |||||||||||
| ?From interface?android.content.ComponentCallbacks | |||||||||||
| ?From interface?android.content.ComponentCallbacks2 |
Constants
public static final int?START_CONTINUATION_MASK
Added in?API level 5Bits returned by?onStartCommand(Intent, int, int)?describing how to continue the service if it is killed. May be?START_STICKY,?START_NOT_STICKY,START_REDELIVER_INTENT, or?START_STICKY_COMPATIBILITY.
Constant Value:?15 (0x0000000f)public static final int?START_FLAG_REDELIVERY
Added in?API level 5This flag is set in?onStartCommand(Intent, int, int)?if the Intent is a re-delivery of a previously delivered intent, because the service had previously returnedSTART_REDELIVER_INTENT?but had been killed before calling?stopSelf(int)?for that Intent.
Constant Value:?1 (0x00000001)public static final int?START_FLAG_RETRY
Added in?API level 5This flag is set in?onStartCommand(Intent, int, int)?if the Intent is a a retry because the original attempt never got to or returned from?onStartCommand(Intent, int, int).
Constant Value:?2 (0x00000002)public static final int?START_NOT_STICKY
Added in?API level 5Constant to return from?onStartCommand(Intent, int, int): if this service's process is killed while it is started (after returning from?onStartCommand(Intent, int, int)), and there are no new start intents to deliver to it, then take the service out of the started state and don't recreate until a future explicit call toContext.startService(Intent). The service will not receive a?onStartCommand(Intent, int, int)?call with a null Intent because it will not be re-started if there are no pending Intents to deliver.
This mode makes sense for things that want to do some work as a result of being started, but can be stopped when under memory pressure and will explicit start themselves again later to do more work. An example of such a service would be one that polls for data from a server: it could schedule an alarm to poll every N minutes by having the alarm start its service. When its?onStartCommand(Intent, int, int)?is called from the alarm, it schedules a new alarm for N minutes later, and spawns a thread to do its networking. If its process is killed while doing that check, the service will not be restarted until the alarm goes off.
Constant Value:?2 (0x00000002)public static final int?START_REDELIVER_INTENT
Added in?API level 5Constant to return from?onStartCommand(Intent, int, int): if this service's process is killed while it is started (after returning from?onStartCommand(Intent, int, int)), then it will be scheduled for a restart and the last delivered Intent re-delivered to it again via?onStartCommand(Intent, int, int). This Intent will remain scheduled for redelivery until the service calls?stopSelf(int)?with the start ID provided to?onStartCommand(Intent, int, int). The service will not receive a?onStartCommand(Intent, int, int)?call with a null Intent because it will will only be re-started if it is not finished processing all Intents sent to it (and any such pending events will be delivered at the point of restart).
Constant Value:?3 (0x00000003)public static final int?START_STICKY
Added in?API level 5Constant to return from?onStartCommand(Intent, int, int): if this service's process is killed while it is started (after returning from?onStartCommand(Intent, int, int)), then leave it in the started state but don't retain this delivered intent. Later the system will try to re-create the service. Because it is in the started state, it will guarantee to call?onStartCommand(Intent, int, int)?after creating the new service instance; if there are not any pending start commands to be delivered to the service, it will be called with a null intent object, so you must take care to check for this.
This mode makes sense for things that will be explicitly started and stopped to run for arbitrary periods of time, such as a service performing background music playback.
Constant Value:?1 (0x00000001)public static final int?START_STICKY_COMPATIBILITY
Added in?API level 5Constant to return from?onStartCommand(Intent, int, int): compatibility version of?START_STICKY?that does not guarantee that?onStartCommand(Intent, int, int)?will be called again after being killed.
Constant Value:?0 (0x00000000)Public Constructors
public?Service?()
Added in?API level 1Public Methods
public final?Application?getApplication?()
Added in?API level 1Return the application that owns this service.
public abstract?IBinder?onBind?(Intent?intent)
Added in?API level 1Return the communication channel to the service. May return null if clients can not bind to the service. The returned?IBinder?is usually for a complex interface that has been?described using aidl.
Note that unlike other application components, calls on to the IBinder interface returned here may not happen on the main thread of the process. More information about the main thread can be found in?Processes and Threads.
?
Parameters
| The Intent that was used to bind to this service, as given to?Context.bindService. Note that any extras that were included with the Intent at that point will?not?be seen here. |
Returns
- Return an IBinder through which clients can call on to the service.
public void?onConfigurationChanged?(Configuration?newConfig)
Added in?API level 1Called by the system when the device configuration changes while your component is running. Note that, unlike activities, other components are never restarted when a configuration changes: they must always deal with the results of the change, such as by re-retrieving resources.
At the time that this function has been called, your Resources object will have been updated to return resource values matching the new configuration.
Parameters
| The new device configuration. |
public void?onCreate?()
Added in?API level 1Called by the system when the service is first created. Do not call this method directly.
public void?onDestroy?()
Added in?API level 1Called by the system to notify a Service that it is no longer used and is being removed. The service should clean up any resources it holds (threads, registered receivers, etc) at this point. Upon return, there will be no more calls in to this Service object and it is effectively dead. Do not call this method directly.
public void?onLowMemory?()
Added in?API level 1This is called when the overall system is running low on memory, and would like actively running process to try to tighten their belt. While the exact point at which this will be called is not defined, generally it will happen around the time all background process have been killed, that is before reaching the point of killing processes hosting service and foreground UI that we would like to avoid killing.
Applications that want to be nice can implement this method to release any caches or other unnecessary resources they may be holding on to. The system will perform a gc for you after returning from this method.
public void?onRebind?(Intent?intent)
Added in?API level 1Called when new clients have connected to the service, after it had previously been notified that all had disconnected in its?onUnbind(Intent). This will only be called if the implementation of?onUnbind(Intent)?was overridden to return true.
Parameters
| The Intent that was used to bind to this service, as given to?Context.bindService. Note that any extras that were included with the Intent at that point will?not?be seen here. |
public void?onStart?(Intent?intent, int startId)
Added in?API level 1?
This method was deprecated in API level 5.
Implement?onStartCommand(Intent, int, int)?instead.
public int?onStartCommand?(Intent?intent, int flags, int startId)
Added in?API level 5Called by the system every time a client explicitly starts the service by calling?startService(Intent), providing the arguments it supplied and a unique integer token representing the start request. Do not call this method directly.
For backwards compatibility, the default implementation calls?onStart(Intent, int)?and returns either?START_STICKY?or?START_STICKY_COMPATIBILITY.
If you need your application to run on platform versions prior to API level 5, you can use the following model to handle the older?onStart(Intent, int)?callback in that case. The?handleCommand?method is implemented by you as appropriate:
// This is the old onStart method that will be called on the pre-2.0// platform. ?On 2.0 or later we override onStartCommand() so this
// method will not be called.
@Override
publicvoid onStart(Intent intent,int startId){
? ? handleCommand(intent);
}
@Override
publicint onStartCommand(Intent intent,int flags,int startId){
? ? handleCommand(intent);
? ? // We want this service to continue running until it is explicitly
? ? // stopped, so return sticky.
? ? return START_STICKY;
}
Note that the system calls this on your service's main thread. A service's main thread is the same thread where UI operations take place for Activities running in the same process. You should always avoid stalling the main thread's event loop. When doing long-running operations, network calls, or heavy disk I/O, you should kick off a new thread, or use?AsyncTask.
?
Parameters
| The Intent supplied to?startService(Intent), as given. This may be null if the service is being restarted after its process has gone away, and it had previously returned anything except?START_STICKY_COMPATIBILITY. |
| Additional data about this start request. Currently either 0,?START_FLAG_REDELIVERY, or?START_FLAG_RETRY. |
| A unique integer representing this specific request to start. Use with?stopSelfResult(int). |
Returns
- The return value indicates what semantics the system should use for the service's current started state. It may be one of the constants associated with theSTART_CONTINUATION_MASK?bits.
See Also
- stopSelfResult(int)
public void?onTaskRemoved?(Intent?rootIntent)
Added in?API level 14This is called if the service is currently running and the user has removed a task that comes from the service's application. If you have setServiceInfo.FLAG_STOP_WITH_TASK?then you will not receive this callback; instead, the service will simply be stopped.
Parameters
| The original root Intent that was used to launch the task that is being removed. |
public void?onTrimMemory?(int level)
Added in?API level 14Called when the operating system has determined that it is a good time for a process to trim unneeded memory from its process. This will happen for example when it goes in the background and there is not enough memory to keep as many background processes running as desired. You should never compare to exact values of the level, since new intermediate values may be added -- you will typically want to compare if the value is greater or equal to a level you are interested in.
To retrieve the processes current trim level at any point, you can use?ActivityManager.getMyMemoryState(RunningAppProcessInfo).
Parameters
| The context of the trim, giving a hint of the amount of trimming the application may like to perform. May be?TRIM_MEMORY_COMPLETE,TRIM_MEMORY_MODERATE,?TRIM_MEMORY_BACKGROUND,?TRIM_MEMORY_UI_HIDDEN,?TRIM_MEMORY_RUNNING_CRITICAL,?TRIM_MEMORY_RUNNING_LOW, orTRIM_MEMORY_RUNNING_MODERATE. |
public boolean?onUnbind?(Intent?intent)
Added in?API level 1Called when all clients have disconnected from a particular interface published by the service. The default implementation does nothing and returns false.
Parameters
| The Intent that was used to bind to this service, as given to?Context.bindService. Note that any extras that were included with the Intent at that point will?not?be seen here. |
Returns
- Return true if you would like to have the service's?onRebind(Intent)?method later called when new clients bind to it.
public final void?startForeground?(int id,?Notification?notification)
Added in?API level 5Make this service run in the foreground, supplying the ongoing notification to be shown to the user while in this state. By default services are background, meaning that if the system needs to kill them to reclaim more memory (such as to display a large page in a web browser), they can be killed without too much harm. You can set this flag if killing your service would be disruptive to the user, such as if your service is performing background music playback, so the user would notice if their music stopped playing.
If you need your application to run on platform versions prior to API level 5, you can use the following model to call the the older setForeground() or this modern method as appropriate:
privatestaticfinalClass<?>[] mSetForegroundSignature =newClass[]{? ? boolean.class};
privatestaticfinalClass<?>[] mStartForegroundSignature =newClass[]{
? ? int.class,Notification.class};
privatestaticfinalClass<?>[] mStopForegroundSignature =newClass[]{
? ? boolean.class};
privateNotificationManager mNM;
privateMethod mSetForeground;
privateMethod mStartForeground;
privateMethod mStopForeground;
privateObject[] mSetForegroundArgs =newObject[1];
privateObject[] mStartForegroundArgs =newObject[2];
privateObject[] mStopForegroundArgs =newObject[1];
void invokeMethod(Method method,Object[] args){
? ? try{
? ? ? ? method.invoke(this, args);
? ? }catch(InvocationTargetException e){
? ? ? ? // Should not happen.
? ? ? ? Log.w("ApiDemos","Unable to invoke method", e);
? ? }catch(IllegalAccessException e){
? ? ? ? // Should not happen.
? ? ? ? Log.w("ApiDemos","Unable to invoke method", e);
? ? }
}
/**
?* This is a wrapper around the new startForeground method, using the older
?* APIs if it is not available.
?*/
void startForegroundCompat(int id,Notification notification){
? ? // If we have the new startForeground API, then use it.
? ? if(mStartForeground !=null){
? ? ? ? mStartForegroundArgs[0]=Integer.valueOf(id);
? ? ? ? mStartForegroundArgs[1]= notification;
? ? ? ? invokeMethod(mStartForeground, mStartForegroundArgs);
? ? ? ? return;
? ? }
? ? // Fall back on the old API.
? ? mSetForegroundArgs[0]=Boolean.TRUE;
? ? invokeMethod(mSetForeground, mSetForegroundArgs);
? ? mNM.notify(id, notification);
}
/**
?* This is a wrapper around the new stopForeground method, using the older
?* APIs if it is not available.
?*/
void stopForegroundCompat(int id){
? ? // If we have the new stopForeground API, then use it.
? ? if(mStopForeground !=null){
? ? ? ? mStopForegroundArgs[0]=Boolean.TRUE;
? ? ? ? invokeMethod(mStopForeground, mStopForegroundArgs);
? ? ? ? return;
? ? }
? ? // Fall back on the old API. ?Note to cancel BEFORE changing the
? ? // foreground state, since we could be killed at that point.
? ? mNM.cancel(id);
? ? mSetForegroundArgs[0]=Boolean.FALSE;
? ? invokeMethod(mSetForeground, mSetForegroundArgs);
}
@Override
publicvoid onCreate(){
? ? mNM =(NotificationManager)getSystemService(NOTIFICATION_SERVICE);
? ? try{
? ? ? ? mStartForeground = getClass().getMethod("startForeground",
? ? ? ? ? ? ? ? mStartForegroundSignature);
? ? ? ? mStopForeground = getClass().getMethod("stopForeground",
? ? ? ? ? ? ? ? mStopForegroundSignature);
? ? ? ? return;
? ? }catch(NoSuchMethodException e){
? ? ? ? // Running on an older platform.
? ? ? ? mStartForeground = mStopForeground =null;
? ? }
? ? try{
? ? ? ? mSetForeground = getClass().getMethod("setForeground",
? ? ? ? ? ? ? ? mSetForegroundSignature);
? ? }catch(NoSuchMethodException e){
? ? ? ? thrownewIllegalStateException(
? ? ? ? ? ? ? ? "OS doesn't have Service.startForeground OR Service.setForeground!");
? ? }
}
@Override
publicvoid onDestroy(){
? ? // Make sure our notification is gone.
? ? stopForegroundCompat(R.string.foreground_service_started);
}
?
Parameters
| The identifier for this notification as per?NotificationManager.notify(int, Notification). |
| The Notification to be displayed. |
See Also
- stopForeground(boolean)
public final void?stopForeground?(boolean removeNotification)
Added in?API level 5Remove this service from foreground state, allowing it to be killed if more memory is needed.
Parameters
| If true, the notification previously provided to?startForeground(int, Notification)?will be removed. Otherwise it will remain until a later call removes it (or the service is destroyed). |
See Also
- startForeground(int, Notification)
public final void?stopSelf?()
Added in?API level 1Stop the service, if it was previously started. This is the same as calling?stopService(Intent)?for this particular service.
See Also
- stopSelfResult(int)
public final void?stopSelf?(int startId)
Added in?API level 1Old version of?stopSelfResult(int)?that doesn't return a result.
See Also
- stopSelfResult(int)
public final boolean?stopSelfResult?(int startId)
Added in?API level 1Stop the service if the most recent time it was started was?startId. This is the same as calling?stopService(Intent)?for this particular service but allows you to safely avoid stopping if there is a start request from a client that you haven't yet seen in?onStart(Intent, int).
Be careful about ordering of your calls to this function.. If you call this function with the most-recently received ID before you have called it for previously received IDs, the service will be immediately stopped anyway. If you may end up processing IDs out of order (such as by dispatching them on separate threads), then you are responsible for stopping them in the same order you received them.
?
Parameters
| The most recent start identifier received in?onStart(Intent, int). |
Returns
- Returns true if the startId matches the last start request and the service will be stopped, else false.
See Also
- stopSelf()
Protected Methods
protected void?dump?(FileDescriptor?fd,?PrintWriter?writer,?String[]?args)
Added in?API level 1Print the Service's state into the given stream. This gets invoked if you run "adb shell dumpsys activity service <yourservicename>". This is distinct from "dumpsys <servicename>", which only works for named system services and which invokes the?dump(FileDescriptor, String[])?method on the?IBinderinterface registered with ServiceManager.
Parameters
| The raw file descriptor that the dump is being sent to. |
| The PrintWriter to which you should dump your state. This will be closed for you after you return. |
| additional arguments to the dump request. |
轉載于:https://www.cnblogs.com/proudToBeAITeer/archive/2013/04/01/2994509.html
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