Android Accelerometer store data in file

Question

I am writing an app in which I have to store data in a file for accelerometer values. How do I do that ? I have to create a file only once and append the data in that file. This is the flow of application:

1. User click on start button, it should start writing sensor data to file.
2. User click on stop button, it should stop writing the data to the file.

Plz help ..

Edit 1: code according to @iTech but it does not append data.

import java.io.*;
import java.util.ArrayList;
import java.util.List;

import app.AccelLocData;

import com.google.android.gms.maps.*;
import com.google.android.gms.maps.GoogleMap.OnMapClickListener;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.Dialog;
import android.content.Context;

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;

import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

public class MapViewActivity extends Activity implements LocationListener,
        SensorEventListener, OnClickListener {

    GoogleMap googleMap;

    private boolean started = false;
    private ArrayList<AccelLocData> sensorData;
    private SensorManager sensorManager;
    private Button btnStart, btnStop;
    private String provider;

    File root, dir, sensorFile;
    FileOutputStream fOut;
    // ObjectOutputStream myOutWriter;
    private Sensor mAccelerometer;
    private FileWriter writer;

    // private Button btnUpload;

    @SuppressLint("NewApi")
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        try {
            root = android.os.Environment.getExternalStorageDirectory();
            dir = new File(root.getAbsolutePath() + "/myapp");
            dir.mkdirs();

            File oldFile = new File(dir, "data.txt");

            boolean deleted = oldFile.delete();
            System.out.println("Delete status = " + deleted);
            sensorFile = new File(dir, "data.txt");

            sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
            mAccelerometer = sensorManager
                    .getDefaultSensor(Sensor.TYPE_ACCELEROMETER);


            btnStart = (Button) findViewById(R.id.btnStart);
            btnStop = (Button) findViewById(R.id.btnStop);
            btnStart.setOnClickListener(this);
            btnStop.setOnClickListener(this);
            btnStart.setEnabled(true);
            btnStop.setEnabled(false);

            int status = GooglePlayServicesUtil
                    .isGooglePlayServicesAvailable(getBaseContext());
            if (status != ConnectionResult.SUCCESS) { // Google Play Services
                                                        // are
                                                        // not available

                int requestCode = 10;
                Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status,
                        this, requestCode);
                dialog.show();

            } else { // Google Play Services are available

                // Getting reference to the SupportMapFragment of
                // activity_main.xml
                // SupportMapFragment supportMapFragment = (MapFragment)
                // getFragmentManager().findFragmentById(R.id.map);

                // Getting GoogleMap object from the fragment
                googleMap = ((MapFragment) getFragmentManager()
                        .findFragmentById(R.id.map)).getMap();
                // googleMap = supportMapFragment.getMap();

                // can use for overlay on the map
                List<Double> latList = new ArrayList<Double>();
                latList.add(45.7309593);
                latList.add(46.34);
                latList.add(47.34);

                List<Double> lonList = new ArrayList<Double>();
                lonList.add(-122.6365384);
                lonList.add(-123.6365384);
                lonList.add(-124.6365384);

                for (int i = 0; i < 3; i++) {
                    // LatLng latLng = new LatLng(45.7309593, -122.6365384);
                    LatLng latLng = new LatLng(latList.get(i).doubleValue(),
                            lonList.get(i).doubleValue());
                    googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
                    googleMap
                            .addMarker(new MarkerOptions()
                                    .position(latLng)
                                    .title("My Spot")
                                    .snippet("This is my spot!")
                                    .icon(BitmapDescriptorFactory
                                            .defaultMarker(BitmapDescriptorFactory.HUE_AZURE)));
                }
                googleMap.setOnMapClickListener(new OnMapClickListener() {

                    @Override
                    public void onMapClick(LatLng latLng) {

                        // Creating a marker
                        MarkerOptions markerOptions = new MarkerOptions();

                        // Setting the position for the marker
                        markerOptions.position(latLng);

                        // Setting the title for the marker.
                        // This will be displayed on taping the marker
                        markerOptions.title(latLng.latitude + " : "
                                + latLng.longitude);

                        // Clears the previously touched position
                        googleMap.clear();

                        // Animating to the touched position
                        googleMap.animateCamera(CameraUpdateFactory
                                .newLatLng(latLng));

                        // Placing a marker on the touched position
                        googleMap.addMarker(markerOptions);
                    }
                });

                // Enabling MyLocation Layer of Google Map
                googleMap.setMyLocationEnabled(true);

                LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

                Criteria criteria = new Criteria();
                provider = locationManager.getBestProvider(criteria, true);
                Location location = locationManager
                        .getLastKnownLocation(provider);

                if (location != null) {
                    onLocationChanged(location);
                }

                locationManager
                        .requestLocationUpdates(provider, 20000, 0, this);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public void onSensorChanged(SensorEvent event) {

        if (started) {

            double x = event.values[0];
            double y = event.values[1];
            double z = event.values[2];

            long timestamp = System.currentTimeMillis();

            LocationManager locManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
            Criteria criteria = new Criteria();
            criteria.setPowerRequirement(Criteria.POWER_MEDIUM);
            criteria.setAccuracy(Criteria.ACCURACY_FINE);

            provider = locManager.getBestProvider(criteria, true);
            Location location = locManager.getLastKnownLocation(provider);

            double latitude = 0;
            double longitude = 0;
            if (location != null) {
                latitude = location.getLatitude();
                longitude = location.getLongitude();
            }
            AccelLocData data = new AccelLocData(timestamp, x, y, z, latitude,
                    longitude);

            System.out.println("data x:" + data.getX());

            try {
                writer.write(data.toString());
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
    }

    @Override
    public void onLocationChanged(Location location) {

        TextView tvLocation = (TextView) findViewById(R.id.tv_location);

        // Getting latitude of the current location
        double latitude = location.getLatitude();

        // Getting longitude of the current location
        double longitude = location.getLongitude();

        // Creating a LatLng object for the current location
        LatLng latLng = new LatLng(latitude, longitude);

        // Showing the current location in Google Map
        googleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));

        // Zoom in the Google Map
        googleMap.animateCamera(CameraUpdateFactory.zoomTo(15));
        // System.out.println("Latitude:" + latitude + ", Longitude:" +
        // longitude);

        // Setting latitude and longitude in the TextView tv_location
        // tvLocation.setText("Latitude:" + latitude + ", Longitude:" +
        // longitude);

    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.btnStart:

            btnStart.setEnabled(false);
            btnStop.setEnabled(true);
            System.out.println("cam on click of start");
            started = true;

            sensorManager.registerListener(this, mAccelerometer,
                    SensorManager.SENSOR_DELAY_FASTEST);
            break;
        case R.id.btnStop:
            try {
                btnStart.setEnabled(true);
                btnStop.setEnabled(false);
                // btnUpload.setEnabled(true);
                started = false;

                sensorManager.unregisterListener(this);

                /*
                 * if(writer != null) { try { writer.close(); } catch
                 * (IOException e) { // TODO Auto-generated catch block
                 * e.printStackTrace(); } }
                 */} catch (Exception e) {
                e.printStackTrace();
            }
            break;
        default:
            break;
        }

    }

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

        if (writer != null) {
            try {
                writer.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

    protected void onResume() {
        super.onResume();
        try {
            System.out.println("called onresume");
            writer = new FileWriter(sensorFile, true);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    @Override
    public void onProviderDisabled(String arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onAccuracyChanged(Sensor arg0, int arg1) {
        // TODO Auto-generated method stub

    }

}

Answer 1

Here is an example code for you to get started.

You can check android samples to learn how to read data from sensors and then just write it to a file.

To run this code, you will need to add two buttons and set their onClick to onStartClick and onStopClick. Also you can specify the output file path to be on the SD card.

public class Main extends Activity implements SensorEventListener {

private SensorManager mSensorManager;
private Sensor mAccelerometer;
private FileWriter writer;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activiy_main);
    mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
    mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
}

public void onStartClick(View view) {
    mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
}

public void onStopClick(View view) {
    mSensorManager.unregisterListener(this);
}
protected void onResume() {
    super.onResume();
    writer = new FileWriter("myfile.txt",true);
}

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

    if(writer != null) {
       writer.close();
    }
}

@Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {

}

@Override
public void onSensorChanged(SensorEvent event) {

    float x = event.values[0];
    float y = event.values[1];
    float z = event.values[2];
    writer.write(x+","+y+","+z+"\n");

 }
}