android service method call invokes null reference error

Question

I am receiving an error when ever I try to call any method of the service on the main activity class.

Error log

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String in.ac.iitkgp.alpha.dbService.getUser()' on a null object reference
                                                                    at in.ac.iitkgp.alpha.MainScreen.onCreateOptionsMenu(MainScreen.java:95)
                                                                    at android.app.Activity.onCreatePanelMenu(Activity.java:2846)
                                                                    at android.support.v4.app.FragmentActivity.onCreatePanelMenu(FragmentActivity.java:341)
                                                                    at android.support.v7.view.WindowCallbackWrapper.onCreatePanelMenu(WindowCallbackWrapper.java:85)
                                                                    at android.support.v7.app.AppCompatDelegateImplBase$AppCompatWindowCallbackBase.onCreatePanelMenu(AppCompatDelegateImplBase.java:258)
                                                                    at android.support.v7.view.WindowCallbackWrapper.onCreatePanelMenu(WindowCallbackWrapper.java:85)
                                                                    at android.support.v7.app.ToolbarActionBar.populateOptionsMenu(ToolbarActionBar.java:454)
                                                                    at android.support.v7.app.ToolbarActionBar$1.run(ToolbarActionBar.java:61)
                                                                    at android.os.Handler.handleCallback(Handler.java:739)
                                                                    at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                    at android.os.Looper.loop(Looper.java:148)
                                                                    at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

I have two activities first activity passes the input to the service and starts it using startService(intent); and calls the next activity. Next activity then binds to the service and reads the input data and changes TextView on the UI. I need to pass it through the service as input is needed in many activities.

Service class

public class dbService extends Service {

private final IBinder Mybinder = new dbBinder();
public String user;
public dbService() {
}

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

public final String getUser(){
   return user;
}


public class dbBinder extends Binder{
    dbService getService(){
        return dbService.this;
    }
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    user = intent.getStringExtra("User");
    return START_NOT_STICKY;
}
}

Snippet from first activity

Intent intent = new Intent(this,MainScreen.class);
    Intent service = new Intent(this,dbService.class);
    String usr = user.getText().toString();
    service.putExtra("User",usr);
    startService(service);
    startActivity(intent);

Snippet from Second activity

dbService Myservice;
boolean bound  = false;
private ServiceConnection connection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        dbBinder binder = (dbBinder) service;
        Myservice = binder.getService();
        bound = true;
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        bound = false;
    }
};

@Override
protected void onCreate(Bundle savedInstanceState) {
.
.
.
Intent i = new Intent(this,dbService.class);
    bindService(i,connection, Context.BIND_AUTO_CREATE);
    TextView user = (TextView) findViewById(R.id.user);
    user.setText(Myservice.getUser());
}

Only accessing the service methods from second activity crashes the app. Everything else seems to work fine. Sorry if it's a dumb question. I am new to java and android app development. Thanks in advance

score 0 · Answer 1 · edited May 12 '16 at 19:07

0

Put the code below in onServiceConnected:

TextView user = (TextView) findViewById(R.id.user); user.setText(Myservice.getUser());`

Unless the service gets connected, you cannot access service object methods.

edited May 12 '16 at 19:07

Vucko

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answered May 12 '16 at 18:00

Sush

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Shouldn't bindService already connect activity to the service and the code below it should execute after the service is connected ? – Ash May 14 '16 at 04:37
No.. You should get the connected first then only you use it. I can see before getting connected your referencing my service object . obviously it will throw an NPE – Sush May 14 '16 at 05:02

android service method call invokes null reference error

1 Answers1