【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;
}
}

@Override
protected 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();
}