Android : Null pointer exception while calling the Invokeservice() inside a tabhost class

Question

I am working on how to bind a service inside a tabhost activity

I have a dependency project named Remoteserviceconnection I am calling inokeservice() inside the tabhost child activity

As I said I have a tabhost activity with three child activities and I want to bind a service inside the child activity and I am getting nul pointer exception.

I went through these two links still I am not getting any Idea

Binding Multiple Activities(Tabs) to a Service using a Base Class Activity

http://code.google.com/p/android/issues/detail?id=2483

I have 4 activities in my project

1) TabBarExample.java 2) FirstTab.java 3) SecondTab.java 4) ThirdTab.java

What exactly I am doing wrong?

Any help is always appreciated, Thanks

Here is my code and I am getting errors in this java file,

FirstTab.java

 public class FirstTab extends Activity {
protected static final String TAG = "HvacActivity";
/** Called when the activity is first created. */
private IMyRemoteService remoteService;
private boolean started = false;
private RemoteServiceConnection conn = null;
private Handler serviceHandler;

private static int speed;
private static int hvactemp;
private static int hvacTemppass;
private Task myTask = new Task();
private ImageView fanimgview;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.hvac);

    if(started == false )
    startService();
    bindService();
    System.gc();

    serviceHandler = new Handler();
    serviceHandler.postDelayed(myTask, 1000L);

}

class RemoteServiceConnection implements ServiceConnection {
    // static final int hvactemp = 0;

    public void onServiceConnected(ComponentName className,
            IBinder boundService) {
        remoteService = IMyRemoteService.Stub
                .asInterface((IBinder) boundService);
        Log.d(getClass().getSimpleName(), "onServiceConnected()");
    }

    public void onServiceDisconnected(ComponentName className) {
        remoteService = null;
        // updateServiceStatus();
        Log.d(getClass().getSimpleName(), "onServiceDisconnected");
    }
};

private void startService() {
    if (started) {
        // Toast.makeText(CarHome.this, "Service already started",
        // Toast.LENGTH_SHORT).show();
    } else {
        Intent i = new Intent();
        i.setClassName("com.msat.home.clusterservices",
                "com.msat.home.clusterservices.RemoteService");
        startService(i);
        started = true;
        updateServiceStatus();
        Log.d(getClass().getSimpleName(), "startService()");
    }

}

private void stopService() {
    if (!started) {
        // drivertmpcount.setText(Integer.toString(hvactemp)); //
        // Toast.makeText(CarHome.this, "Service not yet started",
        // Toast.LENGTH_SHORT).show();
    } else {
        Intent i = new Intent();
        i.setClassName("com.msat.home.clusterservices",
                "com.msat.home.clusterservices.RemoteService");
        stopService(i);
        started = false;
        updateServiceStatus();
        Log.d(getClass().getSimpleName(), "stopService()");
    }
}

private void bindService() {
    if (conn == null) {
        conn = new RemoteServiceConnection();
        Intent i = new Intent();
        i.setClassName("com.msat.home.clusterservices",
                "com.msat.home.clusterservices.RemoteService");
        bindService(i, conn, Context.BIND_AUTO_CREATE);
        updateServiceStatus();
        Log.d(getClass().getSimpleName(), "bindService()");
    } else {
        // Toast.makeText(CarHome.this,
        // "Cannot bind - service already bound",
        // Toast.LENGTH_SHORT).show();
    }
}

private void releaseService() {
    if (conn != null) {
        unbindService(conn);
        conn = null;
        updateServiceStatus();
        Log.d(getClass().getSimpleName(), "releaseService()");
    } else {
        // Toast.makeText(CarHome.this, "Cannot unbind - service not bound",
        // Toast.LENGTH_SHORT).show();
    }
}

private void invokeService() { // getting ERROR here

    if (conn == null) {
        // Toast.makeText(CarHome.this, "Cannot invoke - service not bound",
        // Toast.LENGTH_SHORT).show();
    } else {
        try {
            System.out.println(remoteService);

            final TextView drivertmpcount = (TextView) findViewById(R.id.curtempcount);
            // final TextView tempcountpass = (TextView)
            // findViewById(R.id.tempcountpass);

            hvactemp = remoteService.getHvacTemp();  // getting ERROR here
            hvacTemppass = remoteService.getHvacTemppass();
            System.out.println("Raghav hvac" + hvactemp);

            System.out.println("jaydeep speed" + speed);
            // rpm_text.setText(rpm);

            drivertmpcount.setText(Integer.toString(hvactemp));
            // tempcountpass.setText(Integer.toString(hvacTemppass));

            Log.d(getClass().getSimpleName(), "invokeService()");
        } catch (RemoteException re) {
            Log.e(getClass().getSimpleName(), "RemoteException");
        }
    }
}

private void updateServiceStatus() {
    String bindStatus = conn == null ? "unbound" : "bound";
    String startStatus = started ? "started" : "not started";
    String statusText = "Service status: " + bindStatus + "," + startStatus;
    // TextView t = (TextView)findViewById( R.id.serviceStatus);
    // t.setText( statusText );
    System.out.println("Jaydeep : " + statusText);
}

protected void onDestroy() {
    super.onDestroy();

    releaseService();
    Log.d(getClass().getSimpleName(), "onDestroy()");
}

class Task implements Runnable {
    public void run() {
        invokeService();  // getting ERROR here

        // serviceHandler.postDelayed(this, 1000L);
        //Log.i(getClass().getSimpleName(),
        //      "Incrementing engineRPM in the run method");
    }

}

}

LOGCAT MESSAGES

   09-06 19:12:36.550: E/AndroidRuntime(14116): FATAL EXCEPTION: main
   09-06 19:12:36.550: E/AndroidRuntime(14116): java.lang.NullPointerException
   09-06 19:12:36.550: E/AndroidRuntime(14116):     at com.hvaccontroller.msat.FirstTab.invokeService(FirstTab.java:145)
   09-06 19:12:36.550: E/AndroidRuntime(14116):     at com.hvaccontroller.msat.FirstTab.access$1(FirstTab.java:132)
   09-06 19:12:36.550: E/AndroidRuntime(14116):     at com.hvaccontroller.msat.FirstTab$Task.run(FirstTab.java:180)
  09-06 19:12:36.550: E/AndroidRuntime(14116):  at android.os.Handler.handleCallback(Handler.java:587)
  09-06 19:12:36.550: E/AndroidRuntime(14116):  at android.os.Handler.dispatchMessage(Handler.java:92)
  09-06 19:12:36.550: E/AndroidRuntime(14116):  at android.os.Looper.loop(Looper.java:130)
  09-06 19:12:36.550: E/AndroidRuntime(14116):  at android.app.ActivityThread.main(ActivityThread.java:3686)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at java.lang.reflect.Method.invokeNative(Native Method)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at java.lang.reflect.Method.invoke(Method.java:507)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
 09-06 19:12:36.550: E/AndroidRuntime(14116):   at dalvik.system.NativeStart.main(Native Method)

which is line 145 in FirstTab.java?? – David M Nov 28 '12 at 11:44 — David M, Nov 28 '12 at 11:44
hvactemp = remoteService.getHvacTemp(); is the line no 145 – Randroid Nov 28 '12 at 11:48 — Randroid, Nov 28 '12 at 11:48

Praful Bhatnagar · Accepted Answer · 2012-11-28T11:53:05.990

1

The remoteService object is null at this line of code hvactemp = remoteService.getHvacTemp();.

It looks like that you are expecting that the service would be connected in 1 second. since you are calling the invokeService() after 1 second of calling bindService. In your task check whether the remoteService object is null or not. If the object is not null thencall the invokeService() method if the object is null then register another call back like following:

class Task implements Runnable {
    public void run() {
        if(remoteService !=null){
        invokeService();  // getting ERROR here
         } else{
           serviceHandler.postDelayed(this, 1000L);
         }
        //Log.i(getClass().getSimpleName(),
        //      "Incrementing engineRPM in the run method");
    }

}

Edit1:

Or you can call the you can call the invokeService() method from the onServiceConnected() method to avoid the exception

edited Nov 28 '12 at 11:53

answered Nov 28 '12 at 11:43

Praful Bhatnagar

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Thanks for the reply, but If i have the same code in a separate project with single activity its working fine , is it the problem with the tabhost? – Randroid Nov 28 '12 at 11:47
either way.. the problem is with the appraoch.. you can not expect that you would be able to connect to service in 1 second... try the code I posted or you can call the `invokeService()` from the `onServiceConnected()` method to avoid the exception... – Praful Bhatnagar Nov 28 '12 at 11:50
Thanks again, after adding the code given by you I am not getting any errors but the problem is I am not geting the int value that I wanted to display on the textview this line is not working drivertmpcount.setText(Integer.toString(hvactemp)); here with this I want to display the value on the layout. any help? – Randroid Nov 28 '12 at 11:56
Since you are getting the value from the service you can either show some default text in the text view or show a progress bar in place of or over the test view until you get the value from the service.... – Praful Bhatnagar Nov 28 '12 at 13:36

Android : Null pointer exception while calling the Invokeservice() inside a tabhost class

1 Answers1