/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.app;

import android.annotation.IntDef;
import android.annotation.Nullable;
import android.content.ComponentCallbacks2;
import android.content.ComponentName;
import android.content.Context;
import android.content.ContextWrapper;
import android.content.Intent;
import android.content.res.Configuration;
import android.os.Build;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;

import java.io.FileDescriptor;
import java.io.PrintWriter;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

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(). 
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.
Topics covered here:

What is a Service?
Service Lifecycle
Permissions
Process Lifecycle
Local Service Sample
Remote Messenger Service Sample


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.
 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).

Thus a Service itself is actually very simple, providing two main features:

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. 
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. 
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.
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 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 (calling onCreate while doing so), but does not call onStartCommand(). The client will receive the IBinder object that the service returns from its onBind 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 VERSION_CODES.GINGERBREAD, when using Context.startService(Intent), you can also set 
Intent.FLAG_GRANT_READ_URI_PERMISSION and/or 
Intent.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 ContextWrapper.checkCallingPermission 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 low memory conditions.  However, since
the user is not directly aware of a background service, in that state it is
considered a valid candidate to kill, and you should be prepared for this to
happen.  In particular, long-running services will be increasingly likely to
kill and are guaranteed to be killed (and restarted if appropriate) if they
remain started long enough.
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. The way a client's importance impacts the service's importance can be adjusted through Context.BIND_ABOVE_CLIENT, Context.BIND_ALLOW_OOM_MANAGEMENT, Context.BIND_WAIVE_PRIORITY, Context.BIND_IMPORTANT, and Context.BIND_ADJUST_WITH_ACTIVITY. 
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:
{@sample development/samples/ApiDemos/src/com/example/android/apis/app/LocalService.java
     service}
With that done, one can now write client code that directly accesses the
running service, such as:
{@sample development/samples/ApiDemos/src/com/example/android/apis/app/LocalServiceActivities.java
     bind}

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 of Context.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:
{@sample development/samples/ApiDemos/src/com/example/android/apis/app/MessengerService.java
     service}
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:
{@sample development/samples/ApiDemos/AndroidManifest.xml remote_service_declaration}
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:
{@sample development/samples/ApiDemos/src/com/example/android/apis/app/MessengerServiceActivities.java
     bind}
/**
 * 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
 * {@link android.R.styleable#AndroidManifestService &lt;service&gt;}
 * declaration in its package's <code>AndroidManifest.xml</code>.  Services
 * can be started with
 * {@link android.content.Context#startService Context.startService()} and
 * {@link android.content.Context#bindService Context.bindService()}.
 * 
 * <p>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
 * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html">Processes and
 * Threads</a>.  The {@link IntentService} class is available
 * as a standard implementation of Service that has its own thread where it
 * schedules its work to be done.</p>
 * 
 * <p>Topics covered here:
 * <ol>
 * <li><a href="#WhatIsAService">What is a Service?</a>
 * <li><a href="#ServiceLifecycle">Service Lifecycle</a>
 * <li><a href="#Permissions">Permissions</a>
 * <li><a href="#ProcessLifecycle">Process Lifecycle</a>
 * <li><a href="#LocalServiceSample">Local Service Sample</a>
 * <li><a href="#RemoteMessengerServiceSample">Remote Messenger Service Sample</a>
 * </ol>
 *
 * <div class="special reference">
 * <h3>Developer Guides</h3>
 * <p>For a detailed discussion about how to create services, read the
 * <a href="{@docRoot}guide/topics/fundamentals/services.html">Services</a> developer guide.</p>
 * </div>
 *
 * <a name="WhatIsAService"></a>
 * <h3>What is a Service?</h3>
 * 
 * <p>Most confusion about the Service class actually revolves around what
 * it is <em>not</em>:</p>
 * 
 * <ul>
 * <li> A Service is <b>not</b> 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.
 * <li> A Service is <b>not</b> a thread.  It is not a means itself to do work off
 * of the main thread (to avoid Application Not Responding errors).
 * </ul>
 * 
 * <p>Thus a Service itself is actually very simple, providing two main features:</p>
 * 
 * <ul>
 * <li>A facility for the application to tell the system <em>about</em>
 * 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
 * {@link android.content.Context#startService Context.startService()}, which
 * ask the system to schedule work for the service, to be run until the service
 * or someone else explicitly stop it.
 * <li>A facility for an application to expose some of its functionality to
 * other applications.  This corresponds to calls to
 * {@link android.content.Context#bindService Context.bindService()}, which
 * allows a long-standing connection to be made to the service in order to
 * interact with it.
 * </ul>
 * 
 * <p>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 {@link #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.</p>
 * 
 * <p>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 <a href="#LocalServiceSample">Local Service Sample</a>), to providing
 * a full remoteable interface using AIDL.</p>
 * 
 * <a name="ServiceLifecycle"></a>
 * <h3>Service Lifecycle</h3>
 * 
 * <p>There are two reasons that a service can be run by the system.  If someone
 * calls {@link android.content.Context#startService Context.startService()} then the system will
 * retrieve the service (creating it and calling its {@link #onCreate} method
 * if needed) and then call its {@link #onStartCommand} method with the
 * arguments supplied by the client.  The service will at this point continue
 * running until {@link android.content.Context#stopService Context.stopService()} or
 * {@link #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 {@link #stopSelf(int)} method to ensure the service is
 * not stopped until started intents have been processed.
 * 
 * <p>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(): {@link #START_STICKY} is used for services that are
 * explicitly started and stopped as needed, while {@link #START_NOT_STICKY}
 * or {@link #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.
 * 
 * <p>Clients can also use {@link android.content.Context#bindService Context.bindService()} to
 * obtain a persistent connection to a service.  This likewise creates the
 * service if it is not already running (calling {@link #onCreate} while
 * doing so), but does not call onStartCommand().  The client will receive the
 * {@link android.os.IBinder} object that the service returns from its
 * {@link #onBind} 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 <a href="{@docRoot}guide/components/aidl.html">written
 * in aidl</a>.
 * 
 * <p>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 <em>or</em> there are one or more connections to it with the
 * {@link android.content.Context#BIND_AUTO_CREATE Context.BIND_AUTO_CREATE}
 * flag.  Once neither
 * of these situations hold, the service's {@link #onDestroy} method is called
 * and the service is effectively terminated.  All cleanup (stopping threads,
 * unregistering receivers) should be complete upon returning from onDestroy().
 * 
 * <a name="Permissions"></a>
 * <h3>Permissions</h3>
 * 
 * <p>Global access to a service can be enforced when it is declared in its
 * manifest's {@link android.R.styleable#AndroidManifestService &lt;service&gt;}
 * tag.  By doing so, other applications will need to declare a corresponding
 * {@link android.R.styleable#AndroidManifestUsesPermission &lt;uses-permission&gt;}
 * element in their own manifest to be able to start, stop, or bind to
 * the service.
 *
 * <p>As of {@link android.os.Build.VERSION_CODES#GINGERBREAD}, when using
 * {@link Context#startService(Intent) Context.startService(Intent)}, you can
 * also set {@link Intent#FLAG_GRANT_READ_URI_PERMISSION
 * Intent.FLAG_GRANT_READ_URI_PERMISSION} and/or {@link Intent#FLAG_GRANT_WRITE_URI_PERMISSION
 * Intent.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 {@link #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.
 *
 * <p>In addition, a service can protect individual IPC calls into it with
 * permissions, by calling the
 * {@link #checkCallingPermission}
 * method before executing the implementation of that call.
 * 
 * <p>See the <a href="{@docRoot}guide/topics/security/security.html">Security and Permissions</a>
 * document for more information on permissions and security in general.
 * 
 * <a name="ProcessLifecycle"></a>
 * <h3>Process Lifecycle</h3>
 * 
 * <p>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:
 *
 * <ul>
 * <li><p>If the service is currently executing code in its
 * {@link #onCreate onCreate()}, {@link #onStartCommand onStartCommand()},
 * or {@link #onDestroy onDestroy()} methods, then the hosting process will
 * be a foreground process to ensure this code can execute without
 * being killed.
 * <li><p>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 low memory conditions.  However, since
 * the user is not directly aware of a background service, in that state it <em>is</em>
 * considered a valid candidate to kill, and you should be prepared for this to
 * happen.  In particular, long-running services will be increasingly likely to
 * kill and are guaranteed to be killed (and restarted if appropriate) if they
 * remain started long enough.
 * <li><p>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.  The way a client's importance impacts the service's
 * importance can be adjusted through {@link Context#BIND_ABOVE_CLIENT},
 * {@link Context#BIND_ALLOW_OOM_MANAGEMENT}, {@link Context#BIND_WAIVE_PRIORITY},
 * {@link Context#BIND_IMPORTANT}, and {@link Context#BIND_ADJUST_WITH_ACTIVITY}.
 * <li><p>A started service can use the {@link #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.)
 * </ul>
 * 
 * <p>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 {@link #onStartCommand onStartCommand()}
 * to schedule work to be done asynchronously or in another thread, then you
 * may want to use {@link #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.
 * 
 * <p>Other application components running in the same process as the service
 * (such as an {@link android.app.Activity}) can, of course, increase the
 * importance of the overall
 * process beyond just the importance of the service itself.
 * 
 * <a name="LocalServiceSample"></a>
 * <h3>Local Service Sample</h3>
 * 
 * <p>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.
 * 
 * <p>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.
 * 
 * <p>An example of this use of a Service is shown here.  First is the Service
 * itself, publishing a custom class when bound:
 * 
 * {@sample development/samples/ApiDemos/src/com/example/android/apis/app/LocalService.java
 *      service}
 * 
 * <p>With that done, one can now write client code that directly accesses the
 * running service, such as:
 * 
 * {@sample development/samples/ApiDemos/src/com/example/android/apis/app/LocalServiceActivities.java
 *      bind}
 * 
 * <a name="RemoteMessengerServiceSample"></a>
 * <h3>Remote Messenger Service Sample</h3>
 * 
 * <p>If you need to be able to write a Service that can perform complicated
 * communication with clients in remote processes (beyond simply the use of
 * {@link Context#startService(Intent) Context.startService} to send
 * commands to it), then you can use the {@link android.os.Messenger} class
 * instead of writing full AIDL files.
 * 
 * <p>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:
 * 
 * {@sample development/samples/ApiDemos/src/com/example/android/apis/app/MessengerService.java
 *      service}
 * 
 * <p>If we want to make this service run in a remote process (instead of the
 * standard one for its .apk), we can use <code>android:process</code> in its
 * manifest tag to specify one:
 * 
 * {@sample development/samples/ApiDemos/AndroidManifest.xml remote_service_declaration}
 * 
 * <p>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.
 * 
 * <p>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:
 * 
 * {@sample development/samples/ApiDemos/src/com/example/android/apis/app/MessengerServiceActivities.java
 *      bind}
 */
public abstract class Service extends ContextWrapper implements ComponentCallbacks2 {
    private static final String TAG = "Service";

    
Flag for stopForeground(int): if set, the notification previously provided to startForeground will be removed. Otherwise it will remain until a later call (to startForeground(int, Notification) or stopForeground(int) removes it, or the service is destroyed. /**
     * Flag for {@link #stopForeground(int)}: if set, the notification previously provided
     * to {@link #startForeground} will be removed.  Otherwise it will remain
     * until a later call (to {@link #startForeground(int, Notification)} or
     * {@link #stopForeground(int)} removes it, or the service is destroyed.
     */
    public static final int STOP_FOREGROUND_REMOVE = 1<<0;

    
Flag for stopForeground(int): if set, the notification previously provided to startForeground will be detached from the service. Only makes sense when STOP_FOREGROUND_REMOVE is not set -- in this case, the notification
will remain shown, but be completely detached from the service and so no longer changed
except through direct calls to the notification manager.
/**
     * Flag for {@link #stopForeground(int)}: if set, the notification previously provided
     * to {@link #startForeground} will be detached from the service.  Only makes sense
     * when {@link #STOP_FOREGROUND_REMOVE} is <b>not</b> set -- in this case, the notification
     * will remain shown, but be completely detached from the service and so no longer changed
     * except through direct calls to the notification manager.
     */
    public static final int STOP_FOREGROUND_DETACH = 1<<1;

    
@hide
/** @hide */
    @IntDef(flag = true, prefix = { "STOP_FOREGROUND_" }, value = {
            STOP_FOREGROUND_REMOVE,
            STOP_FOREGROUND_DETACH
    })
    @Retention(RetentionPolicy.SOURCE)
    public @interface StopForegroundFlags {}

    public Service() {
        super(null);
    }

    
Return the application that owns this service. /** Return the application that owns this service. */
    public final Application getApplication() {
        return mApplication;
    }

    
Called by the system when the service is first created.  Do not call this method directly.
/**
     * Called by the system when the service is first created.  Do not call this method directly.
     */
    public void onCreate() {
    }

    
Deprecated:
Implement onStartCommand(Intent, int, int) instead./**
     * @deprecated Implement {@link #onStartCommand(Intent, int, int)} instead.
     */
    @Deprecated
    public void onStart(Intent intent, int startId) {
    }

    
Bits returned by onStartCommand describing how to continue the service if it is killed. May be START_STICKY, START_NOT_STICKY, START_REDELIVER_INTENT, or START_STICKY_COMPATIBILITY. /**
     * Bits returned by {@link #onStartCommand} describing how to continue
     * the service if it is killed.  May be {@link #START_STICKY},
     * {@link #START_NOT_STICKY}, {@link #START_REDELIVER_INTENT},
     * or {@link #START_STICKY_COMPATIBILITY}.
     */
    public static final int START_CONTINUATION_MASK = 0xf;
    
    
Constant to return from onStartCommand: compatibility version of START_STICKY that does not guarantee that onStartCommand will be called again after being killed. /**
     * Constant to return from {@link #onStartCommand}: compatibility
     * version of {@link #START_STICKY} that does not guarantee that
     * {@link #onStartCommand} will be called again after being killed.
     */
    public static final int START_STICKY_COMPATIBILITY = 0;
    
    
Constant to return from onStartCommand: if this service's process is killed while it is started (after returning from onStartCommand), 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 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 to return from {@link #onStartCommand}: if this service's
     * process is killed while it is started (after returning from
     * {@link #onStartCommand}), 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 {@link #onStartCommand} 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.
     * 
     * <p>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.
     */
    public static final int START_STICKY = 1;
    
    
Constant to return from onStartCommand: if this service's process is killed while it is started (after returning from onStartCommand), 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 to Context.startService(Intent). The service will not receive a onStartCommand(Intent, int, int) call with a null Intent because it will not be restarted 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 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 to return from {@link #onStartCommand}: if this service's
     * process is killed while it is started (after returning from
     * {@link #onStartCommand}), 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 to
     * {@link Context#startService Context.startService(Intent)}.  The
     * service will not receive a {@link #onStartCommand(Intent, int, int)}
     * call with a null Intent because it will not be restarted if there
     * are no pending Intents to deliver.
     * 
     * <p>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 {@link #onStartCommand} 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.
     */
    public static final int START_NOT_STICKY = 2;

    
Constant to return from onStartCommand: if this service's process is killed while it is started (after returning from onStartCommand), then it will be scheduled for a restart and the last delivered Intent re-delivered to it again via onStartCommand. This Intent will remain scheduled for redelivery until the service calls stopSelf(int) with the start ID provided to onStartCommand. The service will not receive a onStartCommand(Intent, int, int) call with a null Intent because it will only be restarted 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 to return from {@link #onStartCommand}: if this service's
     * process is killed while it is started (after returning from
     * {@link #onStartCommand}), then it will be scheduled for a restart
     * and the last delivered Intent re-delivered to it again via
     * {@link #onStartCommand}.  This Intent will remain scheduled for
     * redelivery until the service calls {@link #stopSelf(int)} with the
     * start ID provided to {@link #onStartCommand}.  The
     * service will not receive a {@link #onStartCommand(Intent, int, int)}
     * call with a null Intent because it will only be restarted if
     * it is not finished processing all Intents sent to it (and any such
     * pending events will be delivered at the point of restart).
     */
    public static final int START_REDELIVER_INTENT = 3;

    
@hide
/** @hide */
    @IntDef(flag = false, prefix = { "START_" }, value = {
            START_STICKY_COMPATIBILITY,
            START_STICKY,
            START_NOT_STICKY,
            START_REDELIVER_INTENT,
    })
    @Retention(RetentionPolicy.SOURCE)
    public @interface StartResult {}

    
Special constant for reporting that we are done processing onTaskRemoved(Intent). 
@hide
/**
     * Special constant for reporting that we are done processing
     * {@link #onTaskRemoved(Intent)}.
     * @hide
     */
    public static final int START_TASK_REMOVED_COMPLETE = 1000;

    
This flag is set in onStartCommand 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 calling stopSelf(int) for that Intent. /**
     * This flag is set in {@link #onStartCommand} if the Intent is a
     * re-delivery of a previously delivered intent, because the service
     * had previously returned {@link #START_REDELIVER_INTENT} but had been
     * killed before calling {@link #stopSelf(int)} for that Intent.
     */
    public static final int START_FLAG_REDELIVERY = 0x0001;
    
    
This flag is set in onStartCommand if the Intent is a retry because the original attempt never got to or returned from onStartCommand(Intent, int, int). /**
     * This flag is set in {@link #onStartCommand} if the Intent is a
     * retry because the original attempt never got to or returned from
     * {@link #onStartCommand(Intent, int, int)}.
     */
    public static final int START_FLAG_RETRY = 0x0002;

    
@hide
/** @hide */
    @IntDef(flag = true, prefix = { "START_FLAG_" }, value = {
            START_FLAG_REDELIVERY,
            START_FLAG_RETRY,
    })
    @Retention(RetentionPolicy.SOURCE)
    public @interface StartArgFlags {}


    
Called by the system every time a client explicitly starts the service by calling Context.startService, 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 and returns either START_STICKY or START_STICKY_COMPATIBILITY. 
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.
Params:
intent – The Intent supplied to Context.startService, 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.
flags – Additional data about this start request.
startId – A unique integer representing this specific request to start. Use with stopSelfResult(int).
See Also:
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 the START_CONTINUATION_MASK bits./**
     * Called by the system every time a client explicitly starts the service by calling 
     * {@link android.content.Context#startService}, providing the arguments it supplied and a 
     * unique integer token representing the start request.  Do not call this method directly.
     * 
     * <p>For backwards compatibility, the default implementation calls
     * {@link #onStart} and returns either {@link #START_STICKY}
     * or {@link #START_STICKY_COMPATIBILITY}.
     * 
     * <p class="caution">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 {@link android.os.AsyncTask}.</p>
     *
     * @param intent The Intent supplied to {@link android.content.Context#startService}, 
     * 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 {@link #START_STICKY_COMPATIBILITY}.
     * @param flags Additional data about this start request.
     * @param startId A unique integer representing this specific request to 
     * start.  Use with {@link #stopSelfResult(int)}.
     * 
     * @return 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 the {@link #START_CONTINUATION_MASK} bits.
     * 
     * @see #stopSelfResult(int)
     */
    public @StartResult int onStartCommand(Intent intent, @StartArgFlags int flags, int startId) {
        onStart(intent, startId);
        return mStartCompatibility ? START_STICKY_COMPATIBILITY : START_STICKY;
    }
    
    
Called 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.
/**
     * Called 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 onDestroy() {
    }

    public void onConfigurationChanged(Configuration newConfig) {
    }
    
    public void onLowMemory() {
    }

    public void onTrimMemory(int level) {
    }

    
Return 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.
Params:
intent – 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./**
     * Return the communication channel to the service.  May return null if 
     * clients can not bind to the service.  The returned
     * {@link android.os.IBinder} is usually for a complex interface
     * that has been <a href="{@docRoot}guide/components/aidl.html">described using
     * aidl</a>.
     * 
     * <p><em>Note that unlike other application components, calls on to the
     * IBinder interface returned here may not happen on the main thread
     * of the process</em>.  More information about the main thread can be found in
     * <a href="{@docRoot}guide/topics/fundamentals/processes-and-threads.html">Processes and
     * Threads</a>.</p>
     * 
     * @param intent The Intent that was used to bind to this service,
     * as given to {@link android.content.Context#bindService
     * Context.bindService}.  Note that any extras that were included with
     * the Intent at that point will <em>not</em> be seen here.
     * 
     * @return Return an IBinder through which clients can call on to the 
     *         service.
     */
    @Nullable
    public abstract IBinder onBind(Intent intent);

    
Called when all clients have disconnected from a particular interface
published by the service.  The default implementation does nothing and
returns false.
Params:
intent – 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 method later called when new clients bind to it./**
     * Called when all clients have disconnected from a particular interface
     * published by the service.  The default implementation does nothing and
     * returns false.
     * 
     * @param intent The Intent that was used to bind to this service,
     * as given to {@link android.content.Context#bindService
     * Context.bindService}.  Note that any extras that were included with
     * the Intent at that point will <em>not</em> be seen here.
     * 
     * @return Return true if you would like to have the service's
     * {@link #onRebind} method later called when new clients bind to it.
     */
    public boolean onUnbind(Intent intent) {
        return false;
    }
    
    
Called when new clients have connected to the service, after it had previously been notified that all had disconnected in its onUnbind. This will only be called if the implementation of onUnbind was overridden to return true. 
Params:
intent – 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./**
     * Called when new clients have connected to the service, after it had
     * previously been notified that all had disconnected in its
     * {@link #onUnbind}.  This will only be called if the implementation
     * of {@link #onUnbind} was overridden to return true.
     * 
     * @param intent The Intent that was used to bind to this service,
     * as given to {@link android.content.Context#bindService
     * Context.bindService}.  Note that any extras that were included with
     * the Intent at that point will <em>not</em> be seen here.
     */
    public void onRebind(Intent intent) {
    }
    
    
This 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 set ServiceInfo.FLAG_STOP_WITH_TASK then you will not receive this callback; instead, the service will simply be stopped. 
Params:
rootIntent – The original root Intent that was used to launch
the task that is being removed./**
     * This 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
     * set {@link android.content.pm.ServiceInfo#FLAG_STOP_WITH_TASK ServiceInfo.FLAG_STOP_WITH_TASK}
     * then you will not receive this callback; instead, the service will simply
     * be stopped.
     *
     * @param rootIntent The original root Intent that was used to launch
     * the task that is being removed.
     */
    public void onTaskRemoved(Intent rootIntent) {
    }

    
Stop the service, if it was previously started. This is the same as calling Context.stopService for this particular service. 
See Also:
stopSelfResult(int)/**
     * Stop the service, if it was previously started.  This is the same as
     * calling {@link android.content.Context#stopService} for this particular service.
     *  
     * @see #stopSelfResult(int)
     */
    public final void stopSelf() {
        stopSelf(-1);
    }

    
Old version of stopSelfResult that doesn't return a result. 
See Also:
stopSelfResult/**
     * Old version of {@link #stopSelfResult} that doesn't return a result.
     *  
     * @see #stopSelfResult
     */
    public final void stopSelf(int startId) {
        if (mActivityManager == null) {
            return;
        }
        try {
            mActivityManager.stopServiceToken(
                    new ComponentName(this, mClassName), mToken, startId);
        } catch (RemoteException ex) {
        }
    }
    
    
Stop the service if the most recent time it was started was 
startId. This is the same as calling Context.stopService 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. 
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.
Params:
startId – The most recent start identifier received in onStart.
See Also:
stopSelf()
Returns:
Returns true if the startId matches the last start request
and the service will be stopped, else false./**
     * Stop the service if the most recent time it was started was 
     * <var>startId</var>.  This is the same as calling {@link 
     * android.content.Context#stopService} 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 {@link #onStart}. 
     * 
     * <p><em>Be careful about ordering of your calls to this function.</em>.
     * 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.</p>
     * 
     * @param startId The most recent start identifier received in {@link 
     *                #onStart}.
     * @return Returns true if the startId matches the last start request
     * and the service will be stopped, else false.
     *  
     * @see #stopSelf()
     */
    public final boolean stopSelfResult(int startId) {
        if (mActivityManager == null) {
            return false;
        }
        try {
            return mActivityManager.stopServiceToken(
                    new ComponentName(this, mClassName), mToken, startId);
        } catch (RemoteException ex) {
        }
        return false;
    }
    
    
Deprecated:
This is a now a no-op, use startForeground(int, Notification) instead. This method has been turned into a no-op rather than simply being deprecated because analysis of numerous poorly behaving devices has shown that increasingly often the trouble is being caused in part by applications that are abusing it. Thus, given a choice between introducing problems in existing applications using this API (by allowing them to be killed when they would like to avoid it), vs allowing the performance of the entire system to be decreased, this method was deemed less important.
@hide
/**
     * @deprecated This is a now a no-op, use
     * {@link #startForeground(int, Notification)} instead.  This method
     * has been turned into a no-op rather than simply being deprecated
     * because analysis of numerous poorly behaving devices has shown that
     * increasingly often the trouble is being caused in part by applications
     * that are abusing it.  Thus, given a choice between introducing
     * problems in existing applications using this API (by allowing them to
     * be killed when they would like to avoid it), vs allowing the performance
     * of the entire system to be decreased, this method was deemed less
     * important.
     * 
     * @hide
     */
    @Deprecated
    public final void setForeground(boolean isForeground) {
        Log.w(TAG, "setForeground: ignoring old API call on " + getClass().getName());
    }
    
    
If your service is started (running through Context.startService(Intent)), then also make this service run in the foreground, supplying the ongoing notification to be shown to the user while in this state. By default started services are background, meaning that their process won't be given foreground CPU scheduling (unless something else in that process is foreground) and, 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 use startForeground 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. 
Note that calling this method does not put the service in the started state itself, even though the name sounds like it. You must always call ContextWrapper.startService(Intent) first to tell the system it should keep the service running, and then use this method to tell it to keep it running harder.
Apps targeting API VERSION_CODES.P or later must request the permission FOREGROUND_SERVICE.FOREGROUND_SERVICE in order to use this API.
Params:
id – The identifier for this notification as per 
NotificationManager.notify(int, Notification); must not be 0.
notification – The Notification to be displayed.
See Also:
stopForeground(boolean)/**
     * If your service is started (running through {@link Context#startService(Intent)}), then
     * also make this service run in the foreground, supplying the ongoing
     * notification to be shown to the user while in this state.
     * By default started services are background, meaning that their process won't be given
     * foreground CPU scheduling (unless something else in that process is foreground) and,
     * 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 use
     * {@link #startForeground} 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.
     *
     * <p>Note that calling this method does <em>not</em> put the service in the started state
     * itself, even though the name sounds like it.  You must always call
     * {@link #startService(Intent)} first to tell the system it should keep the service running,
     * and then use this method to tell it to keep it running harder.</p>
     *
     * <p>Apps targeting API {@link android.os.Build.VERSION_CODES#P} or later must request
     * the permission {@link android.Manifest.permission#FOREGROUND_SERVICE} in order to use
     * this API.</p>
     *
     * @param id The identifier for this notification as per
     * {@link NotificationManager#notify(int, Notification)
     * NotificationManager.notify(int, Notification)}; must not be 0.
     * @param notification The Notification to be displayed.
     * 
     * @see #stopForeground(boolean)
     */
    public final void startForeground(int id, Notification notification) {
        try {
            mActivityManager.setServiceForeground(
                    new ComponentName(this, mClassName), mToken, id,
                    notification, 0);
        } catch (RemoteException ex) {
        }
    }
    
    
Synonym for stopForeground(int). 
Params:
removeNotification – If true, the STOP_FOREGROUND_REMOVE flag will be supplied.
See Also:
stopForeground(int)
startForeground(int, Notification)/**
     * Synonym for {@link #stopForeground(int)}.
     * @param removeNotification If true, the {@link #STOP_FOREGROUND_REMOVE} flag
     * will be supplied.
     * @see #stopForeground(int)
     * @see #startForeground(int, Notification)
     */
    public final void stopForeground(boolean removeNotification) {
        stopForeground(removeNotification ? STOP_FOREGROUND_REMOVE : 0);
    }

    
Remove this service from foreground state, allowing it to be killed if more memory is needed. This does not stop the service from running (for that you use stopSelf() or related methods), just takes it out of the foreground state. 
Params:
flags – additional behavior options.
See Also:
startForeground(int, Notification)/**
     * Remove this service from foreground state, allowing it to be killed if
     * more memory is needed.  This does not stop the service from running (for that
     * you use {@link #stopSelf()} or related methods), just takes it out of the
     * foreground state.
     *
     * @param flags additional behavior options.
     * @see #startForeground(int, Notification)
     */
    public final void stopForeground(@StopForegroundFlags int flags) {
        try {
            mActivityManager.setServiceForeground(
                    new ComponentName(this, mClassName), mToken, 0, null, flags);
        } catch (RemoteException ex) {
        }
    }

    
Print the Service's state into the given stream. This gets invoked if you run "adb shell dumpsys activity service <yourservicename>" (note that for this command to work, the service must be running, and you must specify a fully-qualified service name). This is distinct from "dumpsys <servicename>", which only works for named system services and which invokes the IBinder.dump method on the IBinder interface registered with ServiceManager. 
Params:
fd – The raw file descriptor that the dump is being sent to.
writer – The PrintWriter to which you should dump your state.  This will be
closed for you after you return.
args – additional arguments to the dump request./**
     * Print the Service's state into the given stream.  This gets invoked if
     * you run "adb shell dumpsys activity service &lt;yourservicename&gt;"
     * (note that for this command to work, the service must be running, and
     * you must specify a fully-qualified service name).
     * This is distinct from "dumpsys &lt;servicename&gt;", which only works for
     * named system services and which invokes the {@link IBinder#dump} method
     * on the {@link IBinder} interface registered with ServiceManager.
     *
     * @param fd The raw file descriptor that the dump is being sent to.
     * @param writer The PrintWriter to which you should dump your state.  This will be
     * closed for you after you return.
     * @param args additional arguments to the dump request.
     */
    protected void dump(FileDescriptor fd, PrintWriter writer, String[] args) {
        writer.println("nothing to dump");
    }

    // ------------------ Internal API ------------------
    
    
@hide
/**
     * @hide
     */
    public final void attach(
            Context context,
            ActivityThread thread, String className, IBinder token,
            Application application, Object activityManager) {
        attachBaseContext(context);
        mThread = thread;           // NOTE:  unused - remove?
        mClassName = className;
        mToken = token;
        mApplication = application;
        mActivityManager = (IActivityManager)activityManager;
        mStartCompatibility = getApplicationInfo().targetSdkVersion
                < Build.VERSION_CODES.ECLAIR;
    }

    
@hide

Clean up any references to avoid leaks./**
     * @hide
     * Clean up any references to avoid leaks.
     */
    public final void detachAndCleanUp() {
        mToken = null;
    }

    final String getClassName() {
        return mClassName;
    }

    // set by the thread after the constructor and before onCreate(Bundle icicle) is called.
    private ActivityThread mThread = null;
    private String mClassName = null;
    private IBinder mToken = null;
    private Application mApplication = null;
    private IActivityManager mActivityManager = null;
    private boolean mStartCompatibility = false;
}