nullpointerexception when activity is trying to communicate with bounded service

Question

I am trying to make my activity communicate with a running background service, but keeps getting a NullPointerException, which doesn't make any sense.. for me at least. Hope someone else can figure out what the problem might be.

First here is my LogCat output:

03-17 20:16:56.390: E/AndroidRuntime(11563): FATAL EXCEPTION: main
03-17 20:16:56.390: E/AndroidRuntime(11563): java.lang.NullPointerException
03-17 20:16:56.390: E/AndroidRuntime(11563):    at com.takenumber.TakeNumber.sendMessageToService(TakeNumber.java:240)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at com.takenumber.TakeNumber$2.onClick(TakeNumber.java:334)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at android.view.View.performClick(View.java:4204)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at android.view.View$PerformClick.run(View.java:17355)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at android.os.Handler.handleCallback(Handler.java:725)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at android.os.Handler.dispatchMessage(Handler.java:92)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at android.os.Looper.loop(Looper.java:137)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at android.app.ActivityThread.main(ActivityThread.java:5041)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at java.lang.reflect.Method.invokeNative(Native Method)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at java.lang.reflect.Method.invoke(Method.java:511)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:817)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
03-17 20:16:56.390: E/AndroidRuntime(11563):    at dalvik.system.NativeStart.main(Native Method)

What I do in my activity:

is to start the service and bind it:

                    serviceIntent = new Intent(context, ServerService.class);                   
                    serviceIntent.putExtra("messageType", StaticValues.MESSAGE_START_SERVICE); 
                    serviceIntent.putExtra("devicetype", StaticValues.DEVICE_TAKENUMBER); 
                    serviceIntent.putExtra("MESSENGER", new Messenger(messageHandler));
                    startService(serviceIntent);
                    bindService(serviceIntent, serviceConnection, Context.BIND_AUTO_CREATE);

and create a serviceConnection:

private ServiceConnection serviceConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            if (isServer) {
                boundServiceServer = ((ServerService.CustomBinder) service).getService();
            } else {
                boundServiceClient = ((ClientService.CustomBinder) service).getService();
            }
        }

        @Override
        public void onServiceDisconnected(ComponentName arg0) {
            boundServiceClient = null;
            boundServiceServer = null;
        }
    };

And then I have a click listener for a button to call a method in my service:

categoryButton.setOnClickListener(new View.OnClickListener() {

                        @Override
                        public void onClick(View v) {
                            Button buttonClicked = (Button)v;
                            int categoryID = v.getId();
                            String categoryTitle = buttonClicked.getText().toString();

                            // TODO: Change to send only to showline devices
                            boundServiceServer.getMessagesFromUI(StaticValues.MESSAGE_NUMBER_TAKEN + StaticValues.MESSAGE_DELIMITER + categoryID + StaticValues.MESSAGE_DELIMITER + categoryTitle);

                        }
                    });

In my service I do this: Create a "binder":

public class CustomBinder extends Binder {
    public ServerService getService() {
        return ServerService.this;
    }
}

The method getMessagesFromUI() in my service (to receive strings from activity) simply looks like this:

public void getMessagesFromUI(String message) {
    // DO stuff
}

Of course onBind() method os overridden:

@Override
public IBinder onBind(Intent arg0) {
    return binder;
}

I really hope someone can figure out the problem as I am completely lost right now. If you need more informatione, just ask.

Edit: Line 240 (NullPointerException) is this one:

boundServiceServer.getMessagesFromUI(messageString);

Additional info:

I've pasted some of my code on pastebin on the following adresses.

The TakeNumber activity is here: http://pastebin.com/DxrWfEYM

And the ServerService is here: http://pastebin.com/7QjiQbTi

I have also inserted "syso"'s in the code to find out what's going on. THis is the logcat output after this:

03-18 14:23:05.740: D/dalvikvm(20260): GC_CONCURRENT freed 213K, 16% free 4276K/5064K, paused 2ms+3ms, total 24ms
03-18 14:23:05.790: I/System.out(20260): server connecting
03-18 14:23:05.810: I/System.out(20260): onBind
03-18 14:23:05.830: D/libEGL(20260): loaded /vendor/lib/egl/libEGL_POWERVR_SGX544_115.so
03-18 14:23:05.840: D/libEGL(20260): loaded /vendor/lib/egl/libGLESv1_CM_POWERVR_SGX544_115.so
03-18 14:23:05.840: D/libEGL(20260): loaded /vendor/lib/egl/libGLESv2_POWERVR_SGX544_115.so
03-18 14:23:05.890: D/OpenGLRenderer(20260): Enabling debug mode 0
03-18 14:23:05.910: I/System.out(20260): server binding
03-18 14:23:05.910: I/System.out(20260): CustomBinder
03-18 14:23:13.710: I/System.out(20260): trying to send to server
03-18 14:23:13.720: D/AndroidRuntime(20260): Shutting down VM
03-18 14:23:13.720: W/dalvikvm(20260): threadid=1: thread exiting with uncaught exception (group=0x41954930)
03-18 14:23:13.720: E/AndroidRuntime(20260): FATAL EXCEPTION: main
03-18 14:23:13.720: E/AndroidRuntime(20260): java.lang.NullPointerException
03-18 14:23:13.720: E/AndroidRuntime(20260):    at com.takenumber.TakeNumber.sendMessageToService(TakeNumber.java:244)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at com.takenumber.TakeNumber$2.onClick(TakeNumber.java:339)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at android.view.View.performClick(View.java:4204)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at android.view.View$PerformClick.run(View.java:17355)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at android.os.Handler.handleCallback(Handler.java:725)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at android.os.Handler.dispatchMessage(Handler.java:92)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at android.os.Looper.loop(Looper.java:137)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at android.app.ActivityThread.main(ActivityThread.java:5041)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at java.lang.reflect.Method.invokeNative(Native Method)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at java.lang.reflect.Method.invoke(Method.java:511)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:817)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
03-18 14:23:13.720: E/AndroidRuntime(20260):    at dalvik.system.NativeStart.main(Native Method)

The app crashes after the button is called, when I try to send data to the service.

Answer 1

I came to a solution myself. I have posted my activity and service code on pastebin.

The Activity: http://pastebin.com/jMgraK2r

The ServerService: http://pastebin.com/yquZAi2i

For some reason, the messenger object from the activity to the service was setting itself to null somehow. By declaring it as static, the problem was solved.

I hope anyone can learn anything from this. Thanks to all the responses above.