【项目总结】-Android Service用法总结

Android Service组件在后台不可见，但一般情况下是与其他组件一同运行在一个进程中的（Local Service与其他部分在一个进程，Remote Service单独开进程），而且在主线程中，并不单独启动一个线程（除非程序员自己另外开线程）

Service组件提供了后台执行某些功能以及为其他应用程序提供服务，提供支撑功能的能力。

生命周期：OnCreate()->OnStartCommand()->OnDestroy()。

调用 Context.startService()可以多次调用，但只要调用stopService一次就会stop.多次调用startService或者bindService不会启动多个服务。

local service样例

public class LocalService extends Service {    private NotificationManager mNM;    // Unique Identification Number for the Notification.    // We use it on Notification start, and to cancel it.    private int 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.     */    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(NOTIFICATION);        // 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.        mNM.notify(NOTIFICATION, notification);    }}

调用

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;    }}@Overrideprotected void onDestroy() {    super.onDestroy();    doUnbindService();}

在Activity中通过mBoundService调用Service中的public方法来获取后台数据，实际上onServiceConnected中返回的是一个IBinder对象，只不过我们在此已经确定Local Service

已经在执行了，可以进行强制类型转换。

Local Service可以通过发送广播来给前台提供后台数据更新，前台只需要注册一个Receiver既可以与Service通讯。

例子：

后台Service的某个方法进行数据更新后执行

Intent intent = new Intent("XXXX_Message");  

sendBroadcast(intent);  通知前台数据已经更新

前台

 private MessageReceiver receiver;
   
class MessageReceiver extends BroadcastReceiver {  
    @Override  
    public void onReceive(Context arg0, Intent arg1) {  
    String action = arg1.getAction();  
        if (action.equals("XXXX_Message")) {  
             //从Service接收广播消息
String msgStr = arg1.getStringExtra("msg_str");
       }
    }  
}  
 
 
 
@Override
protected void onResume() {

super.onResume();

IntentFilter filter = new IntentFilter("XXXX_Message"); 
   if (receiver == null)  
       receiver = new MessageReceiver();  
       //注册BroadcastReceiver  
   registerReceiver(receiver, filter);
}
 


@Override
protected void onPause() {
unregisterReceiver(receiver);  
super.onPause();
}