How to save the streaming sensor data internally on Android?

Question

Cheers. I'm relatively new to Android programming. I've been trying to implement an application that reads the sensor data (accelerometer + gyroscope) then saves it internally with a button click. I was able to get the readings from the sensor successfully. However, only one string of data is saved in a file format, which shows only the current data and previous data was overwritten. Please refer here for the output . Thus, I need some help to fix this.

In the MainActivity.java, I've registered the sensors listener:

@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
    // TODO Auto-generated method stub
}

// Obtain the sensor data from the phone
boolean IsDataRequested = false;
@Override
public void onSensorChanged(SensorEvent event) {
    Sensor sensor = event.sensor;
    if (sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

        if (IsDataRequested == true){

            Log.d("Accelerometer", "Acc_X:" + event.values[0] + "Acc_Y:" + event.values[1] + "Acc_Z:" + event.values[2]);

            AccXText.setText("AccX:" + event.values[0]);
            AccYText.setText("AccY:" + event.values[1]);
            AccZText.setText("AccZ:" + event.values[2]);

            save(event);
        }
    }

    if (sensor.getType() == Sensor.TYPE_GYROSCOPE) {

        if (IsDataRequested == true) {

            Log.d("Gyroscope", "Gyro_X:" + event.values[0] + "Gyro_Y:" + event.values[1] + "Gyro_Z:" + event.values[2]);
            GyroXText.setText("GyroX:" + event.values[0]);
            GyroYText.setText("GyroY:" + event.values[1]);
            GyroZText.setText("GyroZ:" + event.values[2]);

            save(event);
        }
    }

}

Then in the same file, I've created the save method:

public void save(SensorEvent v) {
    float Acc_X = v.values[0];
    float Acc_Y = v.values[1];
    float Acc_Z = v.values[2];

    float Gyro_X = v.values[0];
    float Gyro_Y = v.values[1];
    float Gyro_Z = v.values[2];

    String accString = "Acc=" + "X:" + Acc_X + "Y:" + Acc_Y + "Z:" + Acc_Z;
    String gyroString = "Gyro=" + "X:" + Gyro_X + "Y:" + Gyro_Y + "Z:" + Gyro_Z;

    String FILENAME = "user";

    FileOutputStream fos = null;
    try {
        fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    try {
        fos.write(accString.getBytes());
        fos.write(gyroString.getBytes());
        fos.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Button click to start and stop sending the data:

private OnClickListener myOnSensorsRequestClickHandler = new OnClickListener() {
    @Override
            public void onClick(View sensors) {

            IsDataRequested = !IsDataRequested;
            Log.d("Sensors", "Sensors Button Pressed");

    }
};

My goals are:

1. To have the stream of sensor data saved continuously until the same button is clicked to stop reading the data then it will be saved in one file.

2. The next time I start and stop clicking the button, it will add another saved file, so that I can have multiple files in one folder.

Any help or advice is very much appreciated :)

Answer 1

I hope below suggestion is helpful for your below requirement

    private OnClickListener myOnSensorsRequestClickHandler = new OnClickListener() {
    @Override
            public void onClick(View sensors) {

            IsDataRequested = !IsDataRequested;
            Log.d("Sensors", "Sensors Button Pressed");

            if(IsDataRequested)
            {
            //Create file name when start service button was clicked
        FILENAME = "user"+new Date().getTime() + ".txt"; //Here FILENAME is a path of file in global variable
        }

    }};



    boolean IsDataRequested = false;
    @Override
    public void onSensorChanged(SensorEvent event) {
        Sensor sensor = event.sensor;
        if (sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

            if (IsDataRequested == true){



                Log.d("Accelerometer", "Acc_X:" + event.values[0] + "Acc_Y:" + event.values[1] + "Acc_Z:" + event.values[2]);

                AccXText.setText("AccX:" + event.values[0]);
                AccYText.setText("AccY:" + event.values[1]);
                AccZText.setText("AccZ:" + event.values[2]);

                save(FILENAME, event);
            }
            else
            {

            }
        }

        if (sensor.getType() == Sensor.TYPE_GYROSCOPE) {

            if (IsDataRequested == true) {

                Log.d("Gyroscope", "Gyro_X:" + event.values[0] + "Gyro_Y:" + event.values[1] + "Gyro_Z:" + event.values[2]);
                GyroXText.setText("GyroX:" + event.values[0]);
                GyroYText.setText("GyroY:" + event.values[1]);
                GyroZText.setText("GyroZ:" + event.values[2]);

                save(FILENAME, event);
            }
        }

    }
    public void save(String FILENAME, SensorEvent v) {
        float Acc_X = v.values[0];
        float Acc_Y = v.values[1];
        float Acc_Z = v.values[2];

        float Gyro_X = v.values[0];
        float Gyro_Y = v.values[1];
        float Gyro_Z = v.values[2];


//Here used StringBuffer instead of string for append string data

        StringBuffer accQyroData = "========";
        accQyroData.append("Acc=" + "X:" + Acc_X + "Y:" + Acc_Y + "Z:" + Acc_Z"+"\n"+"Gyro=" + "X:" + Gyro_X + "Y:" + Gyro_Y + "Z:" + Gyro_Z);
        accQyroData.append("========");

        //Use Stream for java append to file when you are dealing with raw data, binary
        appendUsingFileOutputStream(FILENAME, accQyroData);
    }

        /**
         * Use Stream for java append to file when you are dealing with raw data, binary
         * data
         * 
         * @param data
         */
        private static void appendUsingFileOutputStream(String fileName, String data) {
            OutputStream os = null;
            try {
                // below true flag tells OutputStream to append
                os = new FileOutputStream(new File(fileName), true);
                os.write(data.getBytes(), 0, data.length());
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

• To have the stream of sensor data saved continuously until the same button is clicked to stop reading the data then it will be saved in one file.
• The next time I start and stop clicking the button, it will add another saved file, so that I can have multiple files in one folder.