Location API and Google Maps in Android - Tutorial

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by Lars Vogel

Location API and Google Maps in Android - Tutorial

Lars Vogel

Version 3.0

Copyright © 2010 , 2011, 2012 Lars Vogel

15.02.2012

Revision History

Revision 0.1 15.06.2010 Lars

Vogel

created

Revision 0.2 - 3.0 18.06.2010 - 15.02.2012 Lars

Vogel

bugfixes and enhancements

Android Location API and Google Maps

This tutorial describes the usage of the Android Location API, the usage of Google Maps and the Geolocation API. It

is based on Eclipse 3.7, Java 1.6 and Android 4.0 (Ice Cream Sandwich) (Gingerbread).

Table of Contents

1. Android Basics2. Android Location API

2.1. Determine the current geolocation2.2. LocationManager2.3. LocationProvider2.4. Selecting LocationProvider via Criteria2.5. Proximity Alert2.6. Forward and reverse Geocoding2.7. Security2.8. Prompt the user to Enabled GPS

3. Using GPS and setting the current location

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3.1. Activating GPS on the emulator3.2. Setting the geoposition

4. Tutorial: Using the Android Location API

4.1. Create Project4.2. Add permissions4.3. Activity4.4. Run and Test

5. Google Maps

5.1. MapsView5.2. MapsActivity5.3. ItemizedOverlay and OverlayItems5.4. maps library usage declaration

6. Device with Google API7. Google Map key8. Google Maps

8.1. Create Project8.2. Google Map library8.3. Overlays8.4. Layout8.5. Activity8.6. Run and Test

9. Thank you10. Questions and Discussion11. Links and Literature

11.1. Source Code11.2. Android Resources11.3. vogella Resources

1. Android Basics

The following assumes that you have already basic knowledge in Android development. Please check the Android

development tutorial for the basics.

2. Android Location API

2.1. Determine the current geolocation

Most Android devices allow to determine the current geolocation. This can be done via a GPS (Global Positioning

System) device, via cell tower triangulation or via wifi networks.



Android contains the android.location package which provides the API to determine the current geo position.

2.2. LocationManager

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.

2.3. LocationProvider

The LocationProvider class provides location data via the Location class. The LocationProvider class

is the superclass of the different location providers which deliver the information about the current location.

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 then network.

passive Allows to participate in location of updates of other components to save energy

2.4. Selecting LocationProvider via Criteria

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.

2.5. Proximity Alert

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).

2.6. Forward and reverse Geocoding

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.

2.7. Security

If you want to access the GPS sensor, you need the ACCESS_FINE_LOCATION permission. Otherwise you need

the ACCESS_COARSE_LOCATION permission.

2.8. Prompt the user to Enabled GPS

The user can decide if the GPS is enabled or now.

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 the Settings.ACTION_LOCATION_SOURCE_SETTINGS

action for the android.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 settingsif (!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.

3. Using GPS and setting the current location



3.1. Activating GPS on the emulator

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.

3.2. Setting the geoposition

You can use the "DDMS" Perspective of Eclipse to send your geoposition to the emulator or a connected

device. For open this Perspective select Window → Open Perspective → Other → DDMS.

In the Emulator Control part you can enter the geocoordinates and press "Send."

You can als 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

4. Tutorial: Using the Android Location API

4.1. Create Project

Create a new project called "de.vogella.android.locationapi.simple" with the Activity called "ShowLocationActivity".

This example will not use the Google Map therefore, it also runs on an Android device.

Change your "main.xml" layout file from the "res/layout" folder to the following:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_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>

4.2. Add permissions

Add the following permissions to your application in your "AndroidManifest.xml" file

INTERNET

ACCESS_FINE_LOCATION

ACCESS_COARSE_LOCATION

4.3. Activity

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."); int lat = (int) (location.getLatitude()); int lng = (int) (location.getLongitude()); latituteField.setText(String.valueOf(lat)); longitudeField.setText(String.valueOf(lng)); } else { latituteField.setText("Provider not available"); longitudeField.setText("Provider 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(); }}

4.4. Run and Test

If you using the emulator send some geo-coordinates to your device. These geo-coordinate should be displayed as

soon as you press the button.

5. Google Maps

5.1. MapsView

Google provides via the com.google.android.maps package a library for using the MapView class in your

application. This maps allows embedded Google Maps into your application.

You require an additional key to use them. This key will be specified in the View which displays the map.

You need to add the following uses-library statement to your AndroidManifest.xml file. The project creation wizard

does this automatically if you select a Google API version.

<uses-library android:required="true" android:name="com.google.android.maps"></uses-library>



The usage of MapView requires the permission to access the Internet, as the data displayed in the MapView is

downloaded from the Internet.

5.2. MapsActivity

The MapActivity class extends the Activity class and provides the life-cycle management and the services

for displaying a MapView widget.

MapActivity simplify the handling MapViews similar to ListActivity simplifies the usage of ListViews.

A MapView is typically defined in the XML layout file used by the MapActivity and requires the API key in the

"android:apiKey" attribute. A MapView can be used with other user interface components in the same layout.

The MapController class can be used to interact with the MapView, e.g. by moving it. A Geopoint is a

position described via latitude and longitude.

5.3. ItemizedOverlay and OverlayItems

You can put instances of the Overlay class on the map. Overlay is the base class representing an overlay which

may be displayed on top of a map. To add an overlay, subclass this class, create an instance, and add it to the list

obtained from MapView.getOverlays().

ItemizedOverlay

is the base class for an Overlay which consists of a list of OverlayItems.

ItemizedOverlay

handles sorting north-to-south for drawing, creating span bounds, drawing a marker for each point, and maintaining a

focused item. It also matches screen-taps to items, and dispatches Focus-change events to an optional listener.

5.4. maps library usage declaration

You must declare that your application uses the com.google.android.maps library in the application of your

AndroidManifest.xml file. Please note that the usage declaration must be in the application tag otherwise you get

java.lang.ClassNotFoundException for your Activity.

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" package="de.vogella.android.locationapi.maps"



android:versionCode="1" android:versionName="1.0" >

<uses-sdk android:minSdkVersion="15" />

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /> <uses-permission android:name="android.permission.INTERNET" />

<application android:icon="@drawable/ic_launcher" android:label="@string/app_name" > <uses-library android:name="com.google.android.maps" > </uses-library>

<activity android:name="MapViewDemo" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application>

</manifest>

6. Device with Google API

In case you want to use Google Maps in your emulator you have to create a device which supports the Google API's.

This requires that you also install the "Google API". During device creation select the target Google API's in the

version of your SDK.



7. Google Map key

To use Google Maps you need an additional key. See for following description:

http://code.google.com/android/add-ons/google-apis/mapkey.html

This process is a little bit time consuming and involves creating a value on the command line. This values is needed

as input for a website which allow to create the key.



8. Google Maps

8.1. Create Project

Create a new Android project called "de.vogella.android.locationapi.maps" with an Activity called

"ShowMapActivity". Make sure to select the "Google API" als Target.

Add the following permissions to your application.

INTERNET

ACCESS_FINE_LOCATION

ACCESS_COARSE_LOCATION

8.2. Google Map library

You need to add the Google maps library to your application. Add "uses library" to "AndroidManifest.xml".

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" package="de.vogella.android.locationapi.maps" android:versionCode="1" android:versionName="1.0" >

<uses-sdk android:minSdkVersion="15" />

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /> <uses-permission android:name="android.permission.INTERNET" />

<application android:icon="@drawable/ic_launcher" android:label="@string/app_name" > <uses-library android:name="com.google.android.maps" > </uses-library>

<activity android:name="MapViewDemo" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application>



</manifest>

8.3. Overlays

Create the following class. We will later use an image called "point". Put one icon with this name in your drawable

folders. If you don't know where to find icons, you can copy the icons the Android wizard created and placed in the

drawable folders.

package de.vogella.android.locationapi.maps;

import android.graphics.drawable.Drawable;

import com.google.android.maps.ItemizedOverlay;import com.google.android.maps.OverlayItem;

public class MyOverlays extends ItemizedOverlay<OverlayItem> {

private static int maxNum = 3; private OverlayItem overlays[] = new OverlayItem[maxNum]; private int index = 0; private boolean full = false; private MyOverlays itemizedoverlay;

public MyOverlays(Drawable defaultMarker) { super(boundCenterBottom(defaultMarker)); }

@Override protected OverlayItem createItem(int i) { return overlays[i]; }

@Override public int size() { if (full) { return overlays.length; } else { return index; }

}

public void addOverlay(OverlayItem overlay) { if (index < maxNum) { overlays[index] = overlay; } else { index = 0; full = true; overlays[index] = overlay; }



index++; populate(); }

}

8.4. Layout

The next step requires that you have created a valid key for using the MapView widget.

Change the "main.xml" layout file in your "res/layout" folder to the following. and replace "Your Maps API Key" with

your Google Maps API key.

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/mainlayout" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" >

<com.google.android.maps.MapView android:id="@+id/mapview" android:layout_width="fill_parent" android:layout_height="fill_parent" android:apiKey="Your Maps API Key" android:clickable="true" />

</RelativeLayout>

8.5. Activity

Change your Activity to the following. This Activity use an LocationListner to update the MapView

with the current location.

package de.vogella.android.locationapi.maps;

import android.content.Context;import android.graphics.drawable.Drawable;import android.location.Location;import android.location.LocationListener;import android.location.LocationManager;import android.os.Bundle;import android.widget.LinearLayout;

import com.google.android.maps.GeoPoint;import com.google.android.maps.MapActivity;



import com.google.android.maps.MapController;import com.google.android.maps.MapView;import com.google.android.maps.OverlayItem;

public class ShowMapActivity extends MapActivity {

private MapController mapController; private MapView mapView; private LocationManager locationManager; private MyOverlays itemizedoverlay;

public void onCreate(Bundle bundle) { super.onCreate(bundle); setContentView(R.layout.main); // bind the layout to the activity

// create a map view LinearLayout linearLayout = (LinearLayout) findViewById(R.id.main); mapView = (MapView) findViewById(R.id.mapview); mapView.setBuiltInZoomControls(true); // Either satellite or 2d mapView.setSatellite(true); mapController = mapView.getController(); mapController.setZoom(14); // Zoon 1 is world view locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, new GeoUpdateHandler());

Drawable drawable = this.getResources().getDrawable(R.drawable.point); itemizedoverlay = new MyOverlays(drawable); createMarker(); }

@Override protected boolean isRouteDisplayed() { return false; }

public class GeoUpdateHandler implements LocationListener {

@Override public void onLocationChanged(Location location) { int lat = (int) (location.getLatitude() * 1E6); int lng = (int) (location.getLongitude() * 1E6); GeoPoint point = new GeoPoint(lat, lng); createMarker(); mapController.animateTo(point); // mapController.setCenter(point);

}

@Override public void onProviderDisabled(String provider) { }

@Override public void onProviderEnabled(String provider) {



}

@Override public void onStatusChanged(String provider, int status, Bundle extras) { } }

private void createMarker() { GeoPoint p = mapView.getMapCenter(); OverlayItem overlayitem = new OverlayItem(p, "", ""); itemizedoverlay.addOverlay(overlayitem); mapView.getOverlays().add(itemizedoverlay); }}

8.6. Run and Test

Run and test your application. You should be able to zoom in and out and send new geocoordinates to your map via

the Emulator.



It will also draw Overlays on the Map.

9. Thank you

Please help me to support this article:

10. Questions and Discussion



Before posting questions, please see the vogella FAQ. If you have questions or find an error in this article please use

the www.vogella.de Google Group. I have created a short list how to create good questions which might also help

you.

11. Links and Literature

11.1. Source Code

Source Code of Examples

11.2. Android Resources

Introduction to Android Development

Android Location API and Google Maps

Android Homepage

11.3. vogella Resources

Eclipse RCP Training (German) Eclipse RCP Training with Lars Vogel

Android Tutorial Introduction to Android Programming

GWT Tutorial Program in Java and compile to JavaScript and HTML

Eclipse RCP Tutorial Create native applications in Java

JUnit Tutorial Test your application

Git Tutorial Put everything you have under distributed version control system

Documents

Location API and Google Maps in Android - Tutorial