Android Location API
This tutorial describes the usage of the Android Location API. It is based on Eclipse 3.7, Java 1.6 and Android 4.0 (Ice Cream Sandwich).
Table of Contents
The following assumes that you have already basic knowledge in Android development. Please check the Android development tutorial for the basics.
Most Android devices allow to determine the current geolocation. This can be done via a GPS (Global Positioning System) module, via cell tower triangulation or via wifi networks.
Android contains the
android.location package which provides the API to determine the current geo position.The
LocationManager class provides access to the Android location service. This services allows to access location providers, to register location update listeners and proximity alerts and more.The
LocationProvider class is the superclass of the different location providers which deliver the information about the current location. This information is stored in the Location class.The Android device might have several
LocationProvider available and you can select which one you want to use. In most cases you have the followng LocationProvider available.Table 1. LocationProvider
| LocationProvider | Description |
|---|---|
| network | Uses the mobile network or WI-Fi to determine the best location. Might have a higher precision in closed rooms then GPS. |
| gps | Use the GPS receiver in the Android device to determine the best location via satellites. Usually better precision than network. |
| passive | Allows to participate in location of updates of other components to save energy |
For a flexible selection of the best location provider use a
Criteria object, in which you can define how the provider should be selected.You can register a
LocationListener object with the LocationManager class to receive periodic updates about the geoposition.You can also register an
Intent which allows to define a proximity alert, this alert will be triggered if the device enters a area given by a longitude, latitude and radius (proximity alert).The
Geocoder class allows to determine the geo-coordinates (longitude, laditude) for a given address and possible addresses for given geo-coordinates.This process is known as forward and reverse geocoding. The
Geocoder class uses an online Google service.If you want to access the GPS sensor, you need the
ACCESS_FINE_LOCATION permission. Otherwise you need the ACCESS_COARSE_LOCATION permission.The user can decide if the GPS is enabled or not.
You can find out, if a LocationManager is enabled via the
isProviderEnabled() method. If its not enabled you can send the user to the settings via an Intent with theSettings.ACTION_LOCATION_SOURCE_SETTINGS action for theandroid.provider.Settings class.LocationManager service = (LocationManager) getSystemService(LOCATION_SERVICE);
boolean enabled = service
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// check if enabled and if not send user to the GSP settings
// Better solution would be to display a dialog and suggesting to
// go to the settings
if (!enabled) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(intent);
}
Typically you would open an
AlarmDialog prompt the user and if he wants to enable GPS or if the application should be canceled.You cannot enable the GPS directly in your code, the user has to do this.
You need to activate GPS on your test device. If you test on the emulator and its not activated you "null" if you try to use a
LocationManager.The Google Map activity should automatically activate the GPS device in the emulator but if you want to use the location manager directly you need to do this yourself. Currently their seems to be an issue with this.
Start Google Maps on the emulator and request the current geo-position, this will allow you to activate the GPS. Send new GPS coordinates to the Android emulator.
You can use the "DDMS"
Perspective of Eclipse to send your geoposition to the emulator or a connected device. For open this Perspective select → → →.In the Emulator Control part you can enter the geocoordinates and press the button.
You can also set the geoposition the Android emulator via telnet. Open a console and connect to your device. The port number of your device can be seen in the title area of your emulator.
telnet localhost 5554 Set the position via the following command.
geo fix 13.24 52.31
Create a new project called de.vogella.android.locationapi.simple with the Activity calledShowLocationActivity.
This example will not use the Google Map therefore, it also runs on an Android device.
Change your layout file from the
res/layout folder to the following code.<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="40dip"
android:orientation="horizontal" >
<TextView
android:id="@+id/TextView01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dip"
android:layout_marginRight="5dip"
android:text="Latitude: "
android:textSize="20dip" >
</TextView>
<TextView
android:id="@+id/TextView02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="unknown"
android:textSize="20dip" >
</TextView>
</LinearLayout>
<LinearLayout
android:id="@+id/linearLayout2"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<TextView
android:id="@+id/TextView03"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dip"
android:layout_marginRight="5dip"
android:text="Longitute: "
android:textSize="20dip" >
</TextView>
<TextView
android:id="@+id/TextView04"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="unknown"
android:textSize="20dip" >
</TextView>
</LinearLayout>
</LinearLayout>
Add the following permissions to your application in your
AndroidManifest.xml file- INTERNET
- ACCESS_FINE_LOCATION
- ACCESS_COARSE_LOCATION
Change
ShowLocationActivity to the following. It queries the location manager and display the queried values in the activity.package de.vogella.android.locationsapi.simple;
import android.app.Activity;
import android.content.Context;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;
public class ShowLocationActivity extends Activity implements LocationListener {
private TextView latituteField;
private TextView longitudeField;
private LocationManager locationManager;
private String provider;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
latituteField = (TextView) findViewById(R.id.TextView02);
longitudeField = (TextView) findViewById(R.id.TextView04);
// Get the location manager
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
// Define the criteria how to select the locatioin provider -> use
// default
Criteria criteria = new Criteria();
provider = locationManager.getBestProvider(criteria, false);
Location location = locationManager.getLastKnownLocation(provider);
// Initialize the location fields
if (location != null) {
System.out.println("Provider " + provider + " has been selected.");
onLocationChanged(location);
} else {
latituteField.setText("Location not available");
longitudeField.setText("Location not available");
}
}
/* Request updates at startup */
@Override
protected void onResume() {
super.onResume();
locationManager.requestLocationUpdates(provider, 400, 1, this);
}
/* Remove the locationlistener updates when Activity is paused */
@Override
protected void onPause() {
super.onPause();
locationManager.removeUpdates(this);
}
@Override
public void onLocationChanged(Location location) {
int lat = (int) (location.getLatitude());
int lng = (int) (location.getLongitude());
latituteField.setText(String.valueOf(lat));
longitudeField.setText(String.valueOf(lng));
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
}
@Override
public void onProviderEnabled(String provider) {
Toast.makeText(this, "Enabled new provider " + provider,
Toast.LENGTH_SHORT).show();
}
@Override
public void onProviderDisabled(String provider) {
Toast.makeText(this, "Disabled provider " + provider,
Toast.LENGTH_SHORT).show();
}
}
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