Android Google Maps Tutorial

The Android platform provides easy and tight integration between Android applications and Google Maps. The well established Google Maps API is used under the hood in order to bring the power of Google Maps to your Android applications. In this tutorial we will see how to incorporate Google Maps into an Android app.

Installing the Google APIs

In order to be able to use Google Maps, the Google APIs have to be present in your SDK. In case the Google APIs are not already installed, you will have to manually install them. This is accomplished by using the Android SDK and AVD Manager.

Launch the manager and choose the “Installed Options” section to see what is already installed and the “Available Packages” to download the additional APIs.

You can find more information about this procedure in the following links:

• Adding SDK Components
• Installing the Google APIs Add-On

Setting up an Eclipse project

Now that the appropriate tools are installed, let’s proceed with creating a new Android project in Eclipse. The project I created is named “AndroidGoogleMapsProject” and has the following configuration:

It is important to use the “Google APIs” as the target since this option includes the Google extensions that allow you to use Google Maps. Return to the first step of this tutorial if no such option is available in your configuration. I chose the 1.5 version of the platform since we will not be using any of the latest fancy API stuff.

Google Maps API Key Generation

As you might know if you have used the Google Maps API in the past, a key is required in order to be able to use the API. The process is slightly different for use in Android applications, so let’s see what is required to do. Note that the process is described in the “Obtaining a Maps API Key” page, but I will also provide a description here.

First, we have to calculate the MD5 fingerprint of the certificate that we will use to sign the final application. This fingerprint will have to be provided to the Google Maps API service so that it can associate the key with your application. Java’s Key and Certificate Management tool named keytool is used for the fingerprint generation.

The keytool executable resides in the %JAVA_HOME%/bin directory for Windows or $JAVA_HOME/bin for Linux/OS X. For example, in my setup, it is installed in the “C:\programs\Java\jdk1.6.0_18\bin” folder.

While developing an Android application, the application is being signed in debug mode. That is, the SDK build tools automatically sign the application using the debug certificate. This is the certificate whose fingerprint we need to calculate. To generate the MD5 fingerprint of the debug certificate we first need to locate the debug keystore. The location of the keystore varies by platform:

• Windows Vista: C:\Users\\.android\debug.keystore
• Windows XP: C:\Documents and Settings\\.android\debug.keystore
• OS X and Linux: ~/.android/debug.keystore

Now that we have located the keystore, we use the keytool executable to get the MD5 fingerprint of the debug certificate by issuing the following command:

keytool -list -alias androiddebugkey \
-keystore .keystore \
-storepass android -keypass android

For example, in my Windows machine I changed directory to the .android folder and I used the following command:

%JAVA_HOME%/bin/keytool -list -alias androiddebugkey -keystore debug.keystore -storepass android -keypass android

Note that this was executed against the debug keystore, you will have to repeat this for the keystore that will be used with the application you are going to create. Additionally, the application is run on another development environment, with different Android SDK keystore, the API key will be invalid and Google Maps will not work.

The output would be something like the following:

androiddebugkey, Apr 2, 2010, PrivateKeyEntry,
Certificate fingerprint (MD5): 72:BF:25:C1:AF:4C:C1:2F:34:D9:B1:90:35:XX:XX:XX

This the fingerprint we have to provide to the Google Maps service. Now we are ready to sign up for a key by visiting the Android Maps API Key Signup page. After we read and accept the terms and conditions, we provide the generated fingerprint as follows:

We generate the API key and we are presented with the following screen:

Creating the Google Maps application

Finally, its time to write some code. Bookmark the Google APIs Add-On Javadocs for future reference. Integrating Google Maps is quite straightforward and can be achieved by extending the MapActivity class instead of the Activity class that we usually do. The main work is performed by a MapView which displays a map with data obtained from the Google Maps service. A MapActivity is actually a base class with code to manage the boring necessities of any activity that displays a MapView. Activity responsibilities include:

• Activity lifecycle management
• Setup and teardown of services behind a MapView

To extend from MapActivity we have to implement the isRouteDisplayed method, which denotes whether or not we are displaying any kind of route information, such as a set of driving directions. We will not provide such information, so we just return false there.

In our map activity, we will just take reference of a MapView. This view will be defined in the layout XML. We will also use the setBuiltInZoomControls method to enable the built-in zoom controls.

Let’s see how our activity looks like so far:

package com.javacodegeeks.android.googlemaps;

import android.os.Bundle;

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

public class GMapsActivity extends MapActivity {

    private MapView mapView;

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mapView = (MapView) findViewById(R.id.map_view);       
        mapView.setBuiltInZoomControls(true);

    }

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

}

Let’s also see the referenced main.xml layout file:

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 
 xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical" 
 android:layout_width="fill_parent"
 android:layout_height="fill_parent">

 <com.google.android.maps.MapView
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/map_view"
  android:layout_width="fill_parent" 
  android:layout_height="fill_parent"
  android:clickable="true" 
  android:enabled="true" 
  android:apiKey="API-KEY-HERE" />

</RelativeLayout>

Do not forget to provide your API key in the relevant field or else Google Maps will not work.

Launching the application

To test the application we will have to use a device that includes the Google APIs. We will use the AVD manager to create a new device with target set to one of the Google APIs and settings like the following:

If we now launch the Eclipse configuration, we will encounter the following exception:

java.lang.ClassNotFoundException: com.javacodegeeks.android.googlemaps.GMapsActivity in loader dalvik.system.PathClassLoader@435988d0

The problem is that we haven’t notified Android that we wish to use the add-on Google APIs which are external to the base API. To do so, we have to use the uses-library element in our Android manifest file, informing Android that we are going to use classes from the com.google.android.maps package.

Additionally, we have to grant internet access to our application by adding the android.permission.INTERNET directive. Here is how our AndroidManifest.xml file looks like:

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.javacodegeeks.android.googlemaps"
      android:versionCode="1"
      android:versionName="1.0">

    <application android:icon="@drawable/icon" android:label="@string/app_name">

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

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

    </application>

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

</manifest>

And here is what the application screen looks like:

If you click inside the map, the zoom controls will appear and you will be able to zoom in and out.

Adding map overlays

The next step is to add some custom map overlays. To do so, we can extend the Overlay class, which is a base class representing an overlay which may be displayed on top of a map. Alternatively, we may extend the ItemizedOverlay, which is a base class for an Overlay which consists of a list of OverlayItems. Let’s see how we can do this (note that the following example is very similar to the Hello Map View article from the Android documentation):

package com.javacodegeeks.android.googlemaps;

import java.util.ArrayList;

import android.app.AlertDialog;
import android.content.Context;
import android.graphics.drawable.Drawable;

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

public class CustomItemizedOverlay extends ItemizedOverlay<OverlayItem> {

   private ArrayList<OverlayItem> mapOverlays = new ArrayList<OverlayItem>();

   private Context context;

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

   public CustomItemizedOverlay(Drawable defaultMarker, Context context) {
        this(defaultMarker);
        this.context = context;
   }

   @Override
   protected OverlayItem createItem(int i) {
      return mapOverlays.get(i);
   }

   @Override
   public int size() {
      return mapOverlays.size();
   }

   @Override
   protected boolean onTap(int index) {
      OverlayItem item = mapOverlays.get(index);
      AlertDialog.Builder dialog = new AlertDialog.Builder(context);
      dialog.setTitle(item.getTitle());
      dialog.setMessage(item.getSnippet());
      dialog.show();
      return true;
   }

   public void addOverlay(OverlayItem overlay) {
      mapOverlays.add(overlay);
       this.populate();
   }

}

Our class requires an Android Drawable in its constructor, which will be used as a marker. Additionally, the current Context has to be provided. We use an ArrayList to store all the OverlayItems stored in the specific class, so the createItem and size methods are pretty much self-explanatory. The onTap method is called when an item is “tapped” and that could be from a touchscreen tap on an onscreen Item, or from a trackball click on a centered, selected Item. In that method, we just create an AlertDialog and show it to the user. Finally, in the exposed addOverlay method, we add the OverlayItem and invoke the populate method, which is a utility method to perform all processing on a new ItemizedOverlay.

Let’s see how this class can be utilized from our map activity:

package com.javacodegeeks.android.googlemaps;

import java.util.List;

import android.graphics.drawable.Drawable;
import android.os.Bundle;

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

public class GMapsActivity extends MapActivity {

    private MapView mapView;

    private static final int latitudeE6 = 37985339;
    private static final int longitudeE6 = 23716735;

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mapView = (MapView) findViewById(R.id.map_view);       
        mapView.setBuiltInZoomControls(true);

        List mapOverlays = mapView.getOverlays();
        Drawable drawable = this.getResources().getDrawable(R.drawable.icon);
        CustomItemizedOverlay itemizedOverlay = 
             new CustomItemizedOverlay(drawable, this);

        GeoPoint point = new GeoPoint(latitudeE6, longitudeE6);
        OverlayItem overlayitem = 
             new OverlayItem(point, "Hello", "I'm in Athens, Greece!");

        itemizedOverlay.addOverlay(overlayitem);
        mapOverlays.add(itemizedOverlay);

        MapController mapController = mapView.getController();

        mapController.animateTo(point);
        mapController.setZoom(6);

    }

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

}

We create a new instance of our CustomItemizedOverlay class by using the default Android icon as the Drawable. Then we create a GeoPoint pointing to a predefined location and use that to generate an OverlayItem object. We add the overlay item to our CustomItemizedOverlay class and it magically appears in our map on the predefined point.

Finally, we take reference of the underlying MapController and use it to point the map to a specific geographical point using the animateTo method and to define the zoom level by using the setZoom method.

If we launch again the configuration, we will be presented with a zoomed-in map which includes an overlay marker pointing to JavaCodeGeeks home town Athens, Greece. Clicking on the marker will cause the alert dialog to pop-up displaying our custom message.

That’s all guys. A detailed guide on how to integrate Google Maps into your Android application. As always, you can download the Eclipse project created for this tutorial.

Happy mobile coding! And don’t forget to share!

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