Android Service組件在新進程綁定(bindService)過程

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1、首先看兩個例子

   （1）進程內

     Client端

public class CounterService extends Service implements ICounterService {  ......public class CounterBinder extends Binder {  public CounterService getService() {  return CounterService.this;  }  }  ......}

     Server端

public class MainActivity extends Activity implements OnClickListener {  ......private ServiceConnection serviceConnection = new ServiceConnection() {  public void onServiceConnected(ComponentName className, IBinder service) {  counterService = ((CounterService.CounterBinder)service).getService();  Log.i(LOG_TAG, "Counter Service Connected");  }  ......};  ......}

（1）進程間

     Client端

public class RemoteService extends Service {private final static String TAG = "RemoteService";@Overridepublic IBinder onBind(Intent intent) {Log.i(TAG, "執行了OnBind");return new MyBinder();}private class MyBinder extends RemoteWebPage.Stub{@Overridepublic String getCurrentPageUrl() throws RemoteException{return "http://www.cnblogs.com/hibraincol/";}}}

     

     Server端

private class MyServiceConnection implements ServiceConnection{@Overridepublic void onServiceConnected(ComponentName name, IBinder service) {Log.i(TAG, "建立串連...");remoteWebPage = RemoteWebPage.Stub.asInterface(service);try {Log.d(TAG, remoteWebPage.getCurrentPageUrl());} catch (RemoteException e) {// TODO Auto-generated catch blocke.printStackTrace();}}@Overridepublic void onServiceDisconnected(ComponentName name) {Log.i(TAG, "onServiceDisconnected...");}}

     為什麼一個是

counterService = ((CounterService.CounterBinder)service).getService();  

     另一個是

remoteWebPage = RemoteWebPage.Stub.asInterface(service);

     原因在於第一個service是CounterService對象，第二個Service是BinderProxy對象，指向MyBinder對象。

      

      為什麼進程內和進程間會有差別呢？請看：

       就在於第6步，要傳遞的參數是BinderProxy對象。

       進程內會執行如下代碼：

case BINDER_TYPE_HANDLE:               case BINDER_TYPE_WEAK_HANDLE: {                struct binder_ref *ref = binder_get_ref(proc, fp->handle);        ...........         if (ref->node->proc == target_proc) {//相同進程                     if (fp->type == BINDER_TYPE_HANDLE)                         fp->type = BINDER_TYPE_BINDER;                 else                                                   fp->type = BINDER_TYPE_WEAK_BINDER;                 fp->binder = ref->node->ptr;                   fp->cookie = ref->node->cookie;                binder_inc_node(ref->node, fp->type == BINDER_TYPE_BINDER, 0, NULL);                if (binder_debug_mask & BINDER_DEBUG_TRANSACTION)                        printk(KERN_INFO "        ref %d desc %d -> node %d u%p\n",                               ref->debug_id, ref->desc, ref->node->debug_id, ref->node->ptr);        } else {                                               ......        }     }

       為轉換成CounterService對象做準備。
       

       進程間會執行如下代碼：

case BINDER_TYPE_HANDLE:               case BINDER_TYPE_WEAK_HANDLE: {                struct binder_ref *ref = binder_get_ref(proc, fp->handle);        .........        if (ref->node->proc == target_proc) {                         .....        } else {//不同進程                                          struct binder_ref *new_ref;                    new_ref = binder_get_ref_for_node(target_proc, ref->node);                if (new_ref == NULL) {                                         return_error = BR_FAILED_REPLY;                        goto err_binder_get_ref_for_node_failed;                }                                              fp->handle = new_ref->desc;                    binder_inc_ref(new_ref, fp->type == BINDER_TYPE_HANDLE, NULL);                if (binder_debug_mask & BINDER_DEBUG_TRANSACTION)                        printk(KERN_INFO "        ref %d desc %d -> ref %d desc %d (node %d)\n",                               ref->debug_id, ref->desc, new_ref->debug_id, new_ref->desc, ref->node->debug_id);        }     }

        為轉換成BinderProxy對象做準備。此時BinderProxy對象是Counter進程的，MyBinder對象是CounterService進程的。它們通過處理序間通訊的方式傳遞資料。