ROS Subscriber in Android

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I would like to make a Subscriber on my Android-Application which can subscribe the batterydata from the robotino. These Data should be displayed on the apply. In this project i have two nodes which the predecessor make it. In one of then they subscribe the camera an, which I use the source code to hope they working for my extra function, but they show nothing. Here my Sourcecode for the subscription

@Override
public void onStart(ConnectedNode connectedNode) {
 // Battery Subscriber
    battery_subscriber = connectedNode.newSubscriber(GraphName.of(topic_basename + "battery_status"), std_msgs.Float64._TYPE);
    battery_subscriber.addMessageListener(new MessageListener<std_msgs.Float64>() {
        @Override
        public void onNewMessage(Float64 message) {
            batterystatus = callable.call(message);
        }
    });                                                                                                                                                                            public Float64 getBatterystatus() { return batterystatus;
}

In my MainActivity I call the "getBatterystatus" to receive the data from the battery:

    pTextBatteryStatus = (TextView) findViewById(R.id.robot_battery);
    pTextBatteryStatus.setText(String.valueOf(NodeTeleopPublisher.getBatterystatus()));

I publish some data but my app is crashing all the time. My Question is: How make a simple Subscriber for my Android-Application?

Edit: Thank you for your answer. I hope that is the errorlog what are your need. The app crash doesnt make some error. I think the problem is the part from the messageListener.

05-24 15:03:03.659 28077-28077/? E/HAL: load: couldn't find symbol HMI
05-24 15:03:03.660 28077-28077/? E/memtrack: Couldn't load memtrack module (Invalid argument)
05-24 15:03:03.660 28077-28077/? E/android.os.Debug: failed to load memtrack module: -22
05-24 15:03:03.708 28077-28077/? E/HAL: load: id=fm != hmi->id=fm
05-24 15:03:03.708 28077-28077/? E/fm_if.c: find the id:fm and begins to open the devices
05-24 15:03:04.954 28092-28092/? E/HAL: load: couldn't find symbol HMI
05-24 15:03:04.955 28092-28092/? E/memtrack: Couldn't load memtrack module (Invalid argument)
05-24 15:03:04.955 28092-28092/? E/android.os.Debug: failed to load memtrack module: -22
05-24 15:03:05.003 28092-28092/? E/HAL: load: id=fm != hmi->id=fm
05-24 15:03:05.003 28092-28092/? E/fm_if.c: find the id:fm and begins to open the devices
05-24 15:03:05.785 27146-27174/? E/ExternalAccountType: Unsupported attribute readOnly
05-24 15:03:05.785 27146-27174/? E/CSP_ExceptionCapture: Unsupported attribute readOnly
05-24 15:03:05.901 5459-5497/? E/LogCollectService: Level = 256
05-24 15:03:11.144 28104-28104/? E/HAL: load: couldn't find symbol HMI
05-24 15:03:11.144 28106-28106/? E/HAL: load: couldn't find symbol HMI
05-24 15:03:11.144 28106-28106/? E/memtrack: Couldn't load memtrack module (Invalid argument)
05-24 15:03:11.144 28104-28104/? E/memtrack: Couldn't load memtrack module (Invalid argument)
05-24 15:03:11.144 28106-28106/? E/android.os.Debug: failed to load memtrack module: -22
05-24 15:03:11.144 28104-28104/? E/android.os.Debug: failed to load memtrack module: -22
05-24 15:03:11.202 28106-28106/? E/HAL: load: id=fm != hmi->id=fm
05-24 15:03:11.202 28104-28104/? E/HAL: load: id=fm != hmi->id=fm
05-24 15 ...