Android GPS Example

Android GPS Example

April 11th, 2010

For some reason there doesn’t seem to be a clear example showing how to use GPS on Android. Here is some code I have written that listens for location changes and displays the data in a TextView. The example also shows how to open the GPS setting with code via an Intent, since sometimes the GPS will be turned off by the user.
Code

package uk.co.hejp.GPSExample;

import android.app.Activity;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.location.LocationProvider;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;

public class Main extends Activity implements LocationListener {

	/* this class implements LocationListener, which listens for both
	 * changes in the location of the device and changes in the status
	 * of the GPS system.
	 * */

	static final String tag = "Main"; // for Log

	TextView txtInfo;
	LocationManager lm;
	StringBuilder sb;
	int noOfFixes = 0;

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		/* get TextView to display the GPS data */
		txtInfo = (TextView) findViewById(R.id.textInfo);

		/* the location manager is the most vital part it allows access
		 * to location and GPS status services */
		lm = (LocationManager) getSystemService(LOCATION_SERVICE);
	}

	@Override
	protected void onResume() {
		/*
		 * onResume is is always called after onStart, even if the app hasn't been
		 * paused
		 *
		 * add location listener and request updates every 1000ms or 10m
		 */
		lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 10f, this);
		super.onResume();
	}

	@Override
	protected void onPause() {
		/* GPS, as it turns out, consumes battery like crazy */
		lm.removeUpdates(this);
		super.onResume();
	}

	@Override
	public void onLocationChanged(Location location) {
		Log.v(tag, "Location Changed");

		sb = new StringBuilder(512);

		noOfFixes++;

		/* display some of the data in the TextView */

		sb.append("No. of Fixes: ");
		sb.append(noOfFixes);
		sb.append('\n');
		sb.append('\n');

		sb.append("Londitude: ");
		sb.append(location.getLongitude());
		sb.append('\n');

		sb.append("Latitude: ");
		sb.append(location.getLatitude());
		sb.append('\n');

		sb.append("Altitiude: ");
		sb.append(location.getAltitude());
		sb.append('\n');

		sb.append("Accuracy: ");
		sb.append(location.getAccuracy());
		sb.append('\n');

		sb.append("Timestamp: ");
		sb.append(location.getTime());
		sb.append('\n');

		txtInfo.setText(sb.toString());
	}

	@Override
	public void onProviderDisabled(String provider) {
		/* this is called if/when the GPS is disabled in settings */
		Log.v(tag, "Disabled");

		/* bring up the GPS settings */
		Intent intent = new Intent(
				android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
		startActivity(intent);
	}

	@Override
	public void onProviderEnabled(String provider) {
		Log.v(tag, "Enabled");
		Toast.makeText(this, "GPS Enabled", Toast.LENGTH_SHORT).show();

	}

	@Override
	public void onStatusChanged(String provider, int status, Bundle extras) {
		/* This is called when the GPS status alters */
		switch (status) {
		case LocationProvider.OUT_OF_SERVICE:
			Log.v(tag, "Status Changed: Out of Service");
			Toast.makeText(this, "Status Changed: Out of Service",
					Toast.LENGTH_SHORT).show();
			break;
		case LocationProvider.TEMPORARILY_UNAVAILABLE:
			Log.v(tag, "Status Changed: Temporarily Unavailable");
			Toast.makeText(this, "Status Changed: Temporarily Unavailable",
					Toast.LENGTH_SHORT).show();
			break;
		case LocationProvider.AVAILABLE:
			Log.v(tag, "Status Changed: Available");
			Toast.makeText(this, "Status Changed: Available",
					Toast.LENGTH_SHORT).show();
			break;
		}
	}

	@Override
	protected void onStop() {
		/* may as well just finish since saving the state is not important for this toy app */
		finish();
		super.onStop();
	}
}

Permissions
Of course the Android framework has security permissions to protect the user. To get the permission to use GPS add a uses-permission tag with attribute android:name set to “android.permission.ACCESS_FINE_LOCATION” to the AndroidManifest.xml document as a direct child of the manifest tag, i.e:

	 android:name="android.permission.ACCESS_FINE_LOCATION" />

Notes
When testing this code in the emulator, you can send mock fixes by connecting to the emulator using telnet, i.e. ‘telnet localhost 5554′ and typing:
geo fix -10.223, 40.549