Service服务

public class LocalService extends Service {
    private NotificationManager mNM;

    /**
     * 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.
     */
    public class LocalBinder extends Binder {
        LocalService getService() {
            return LocalService.this;
        }
    }

    @Override
    public void onCreate() {
        mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);

        // Display a notification about us starting.  We put an icon in the status bar.
        showNotification();
    }

    @Override
    public int 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
    public void onDestroy() {
        // Cancel the persistent notification.
        mNM.cancel(R.string.local_service_started);

        // Tell the user we stopped.
        Toast.makeText(this, R.string.local_service_stopped, Toast.LENGTH_SHORT).show();
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    // This is the object that receives interactions from clients.  See
    // RemoteService for a more complete example.
    private final IBinder mBinder = new LocalBinder();

    /**
     * Show a notification while this service is running.
     */
    private void 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 = new Notification(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,
                new Intent(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.
        // We use a layout id because it is a unique number.  We use it later to cancel.
        mNM.notify(R.string.local_service_started, notification);
    }
}

private LocalService mBoundService;

private ServiceConnection mConnection = new ServiceConnection() {
    public void 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();
    }

    public void 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(new Intent(Binding.this, 
            LocalService.class), mConnection, Context.BIND_AUTO_CREATE);
    mIsBound = true;
}

void doUnbindService() {
    if (mIsBound) {
        // Detach our existing connection.
        unbindService(mConnection);
        mIsBound = false;
    }
}

@Override
protected void onDestroy() {
    super.onDestroy();
    doUnbindService();
}

public class MessengerService extends Service {
    /** For showing and hiding our notification. */
    NotificationManager mNM;
    /** Keeps track of all current registered clients. */
    ArrayList<Messenger> mClients = new ArrayList<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.
     */
    static final int 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.
     */
    static final int 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.
     */
    static final int MSG_SET_VALUE = 3;

    /**
     * Handler of incoming messages from clients.
     */
    class IncomingHandler extends Handler {
        @Override
        public void 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.
     */
    final Messenger mMessenger = new Messenger(new IncomingHandler());

    @Override
    public void onCreate() {
        mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);

        // Display a notification about us starting.
        showNotification();
    }

    @Override
    public void 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
    public IBinder onBind(Intent intent) {
        return mMessenger.getBinder();
    }

    /**
     * Show a notification while this service is running.
     */
    private void 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 = new Notification(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,
                new Intent(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);
    }
}

<service android:name=".app.MessengerService"
        android:process=":remote" />

/** 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.
 */
class IncomingHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case MessengerService.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.
 */
final Messenger mMessenger = new Messenger(new IncomingHandler());

/**
 * Class for interacting with the main interface of the service.
 */
private ServiceConnection mConnection = new ServiceConnection() {
    public void 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 = new Messenger(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();
    }

    public void 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(new Intent(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.");
    }
}