Java – Gravity sensing value increases

The

gravity sensor value is incremented after each call to the onSensorChanged(SensorEvent event) event value. The value increases and reaches the NaN value after a little time (about 1 minute). Can someone say why this is so?
Code:

private void recordData(SensorEvent e) {
    String label;
    int currentSensorId = -1;
    switch (e.sensor.getType()) {
    case Sensor.TYPE_ACCELEROMETER:
        currentSensorId = 0;
        label = LOG_LABEL_ACCELEROMETER;
        break;
    case Sensor.TYPE_GYROSCOPE:
        label = LOG_LABEL_GYROSCOPER;
        currentSensorId = 1;
        break;
    case Sensor.TYPE_GRAVITY:
        label = LOG_LABEL_GRAVITY;
        currentSensorId = 2;
        break;
    case Sensor.TYPE_ROTATION_VECTOR:
        label = LOG_LABEL_ROTATION_VECTOR;
        currentSensorId = 3;
        break;
    default:
        label = "UNKNOWN SENSOR TYPE!";
        break;
    }
    if (currentSensorId == -1)
        return;

 Force set events frequency to value from config,
     cause sensor events minimal frequency = 0.2 sec.
    timePassed[currentSensorId] = System.currentTimeMillis()
            - lastSensorEventTime[currentSensorId];
    if (timePassed[currentSensorId] < Config.SENSOR_DELAY_MILLISEC) {
        return;
    } else {
        lastSensorEventTime[currentSensorId] = System.currentTimeMillis();
    }

if (this.pauseRecordingData || checkSDCardMemory())
        return;
    fileWriter.writeEvent(label, System.currentTimeMillis(), e.values);
}

public void writeEvent(String eventSource, long timestamp, float[] values) {
        Log.d(TAG, "writeEvent(); eventSource = " + eventSource);       

if ( !this.fileExists ) createNewFile();        
    try {       
        String valuesString = eventSource + "\t" + String.format( "%d\t", timestamp);

for (int i = 0; i < values.length; i++) {
            valuesString += String.format( "%f\t",values[i]);
            Log.d(TAG, "writeEvent(); values[" + i + "] = " + values[i]);
    }           
        buffWriter.append(valuesString + "\n");
    } catch (IOException e1) {              
          e1.printStackTrace();
          Log.d(TAG,"RECORDING EVENT TO FILE FAILED!");
    }               
}

There are two possibilities:

1. Most likely: Your code has errors, such as you didn’t reset variables or add values (read for details). http://developer.android.com/guide/topics/sensors/sensors_motion.html)。

2. Your gravity sensor is broken (to check this, try another device).

For more help, post your code, How you can access and manage the values read from the gravity sensor.

Edit:

As I mentioned, there is an error in your code. Sensor read latency should be set to one of the possible options:

int     SENSOR_DELAY_FASTEST     get sensor data as fast as possible
int     SENSOR_DELAY_GAME        rate suitable for games
int     SENSOR_DELAY_NORMAL      rate (default) suitable for screen orientation changes
int     SENSOR_DELAY_UI          rate suitable for the user interface 

!!! instead of custom values

Thanks for finding the solution.