AIDL ipc messaging caused nullpointerexception

Question

我有一個服務，在後臺工作，並且每隔一段時間接收消息。 我希望應用能夠連接到我的服務並接收這些消息。 所以我做的是使用AIDL實現IPC。我已經創建了兩個AIDL文件： 「IExtMessage」：

package com.tfl.extprotocolservice; 
import com.tfl.extprotocolservice.ICallBackMessage; 



interface IExtMessage{ 
    void getMessage(ICallBackMessage cb); 
} 

和 「ICallBackMessage」：

package com.tfl.extprotocolservice; 

interface ICallBackMessage{ 
void onMessageReceived(int parameter,int state); 
} 

，並創建了一個會收到這些形式交往，以測試這個IPC的應用程序：

public class MainActivity extends Activity implements ServiceConnection{ 
    private IExtMessage binding=null; 
    private parseParametersTask task=null; 
    HashMap<Integer,List<String>> parameters; 
    ParameterAlert alert; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     connectToService(); 
     task=new parseParametersTask(); 
     task.execute(); 
     parameters=ReadParams.params; 





    } 

    public void connectToService(){ 
     Intent implicit=new Intent(IExtMessage.class.getName()); 
     List<ResolveInfo> matches=getPackageManager().queryIntentServices(implicit, 0); 
     if(matches.size()==0){ 
      Toast.makeText(getApplicationContext(), "Cannot find a matching service!", Toast.LENGTH_LONG).show(); 
     } 
     else if (matches.size()>1){ 
      Toast.makeText(getApplicationContext(), "Found multiple matching services!", Toast.LENGTH_LONG).show(); 
     } 
     else{ 
      Toast.makeText(getApplicationContext(), "Found the Protocol Service", Toast.LENGTH_LONG).show(); 
      Intent explicit=new Intent(implicit); 
      ServiceInfo svcInfo=matches.get(0).serviceInfo; 
      ComponentName cn=new ComponentName(svcInfo.applicationInfo.packageName, svcInfo.name); 
      explicit.setComponent(cn); 
      bindService(explicit, this, Context.BIND_AUTO_CREATE); 



     } 
    } 

    public void buttonClick(View v) { 
     if (v.getId() == R.id.navigation) { 
      DialogFragment dialog = new navigationChooserFragment(); 
      dialog.show(getFragmentManager(), "navigation"); 
     } 
     if(v.getId()==R.id.ptt){ 
      PackageManager pm=getPackageManager(); 
      Intent i=pm.getLaunchIntentForPackage("com.loudtalks"); 
      i.addCategory(Intent.CATEGORY_LAUNCHER); 
      startActivity(i); 
     } 

    } 

    @Override 
    public void onServiceConnected(ComponentName name, IBinder service) { 
     Log.d("SERVICE", "Service Connected"); 
     binding=IExtMessage.Stub.asInterface(service); 
     try { 
      binding.getMessage(cb); 
     } catch (RemoteException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 
    } 

    @Override 
    public void onServiceDisconnected(ComponentName name) { 
     Log.d("SERVICE","Service disconnected :("); 
     binding=null; 

    } 

    ICallBackMessage.Stub cb=new ICallBackMessage.Stub() { 

     @Override 
     public void onMessageReceived(int parameter,int state) throws RemoteException { 
      Log.d("SERVICE","received parameter "+parameter); 
      Log.d("SERVICE", "received state " + state); 
      FragmentManager fm=getFragmentManager(); 
      FragmentTransaction ft=fm.beginTransaction(); 
      if(state==1){ 
       alert=new ParameterAlert(); 
       Bundle bundleParam=new Bundle(); 
       bundleParam.putInt("parameter",parameter); 
       alert.setArguments(bundleParam); 
       alert.show(ft,"alert"); 
      }else { 
       if (alert.isVisible()) { 
        alert.dismiss(); 
       } 
      } 
     } 
    }; 

    class parseParametersTask extends AsyncTask<Void,Void,Void>{ 

     @Override 
     protected Void doInBackground(Void... params) { 
      ReadParams readParams =new ReadParams(); 
      try { 
       readParams.setInputFile(getAssets().open("parameters.xls")); 
       readParams.read(); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 

      return null; 
     } 
    } 

} 

這是我的服務的相關代碼：

public IBinder onBind(Intent intent) { 

     return (new ExtMessageBinder()); 


} 


    private static class ExtMessageBinder extends IExtMessage.Stub { 
    @Override 
    public void getMessage(ICallBackMessage cb) throws RemoteException { 
     L.m("TESTSERVICE","getMessage in Service called"); 

     cb1 = cb; 

    } 

} 

cb1是收到消息時保存的靜態ICallBackMessage變量。 和我的服務，這是傳遞消息監聽器：

 try { 
      cb1.onMessageReceived(carParameter, state); 
     } catch (RemoteException e1) { 
      // TODO Auto-generated catch block 
      L.m("TESTSERVICE", "" + e1); 
     } 

所以，問題是，有時一切都很正常，但有時我的服務崩潰與此異常：

05-11 13:55:28.763: E/AndroidRuntime(1924): FATAL EXCEPTION: main 
05-11 13:55:28.763: E/AndroidRuntime(1924): java.lang.NullPointerException 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at android.os.Parcel.readException(Parcel.java:1333) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at android.os.Parcel.readException(Parcel.java:1281) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at com.tfl.extprotocolservice.ICallBackMessage$Stub$Proxy.onMessageReceived(ICallBackMessage.java:83) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at com.tfl.extprotocolservice.ExtProtocolService$1.handleMessage(ExtProtocolService.java:127) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at android.os.Handler.dispatchMessage(Handler.java:99) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at android.os.Looper.loop(Looper.java:137) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at android.app.ActivityThread.main(ActivityThread.java:4424) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at java.lang.reflect.Method.invokeNative(Native Method) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at java.lang.reflect.Method.invoke(Method.java:511) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
05-11 13:55:28.763: E/AndroidRuntime(1924):  at dalvik.system.NativeStart.main(Native Method) 

我不不知道爲什麼會發生，也許我在某處或某處發生了泄漏。 我看到處處都找不到答案。

Answer 1

您的源代碼看起來不錯。我真的不知道什麼是問題。你可以嘗試單向使用& out關鍵字。我寫了一個簡單的演示here，看看你是否想要。