This article is targeted
to a beginner who wants to implement GPS
functionality and work with Google Maps API as well. Before going to the
progrmming, you need to know about API Key and Key Store File.
The first and foremost
thing is getting a Google Maps API key. Getting one is relatively easy but it
requires our application to be signed with a certificate and notify Google
about Hash (MD5) fingerprint of the certificate.
Generating MD5 Key and Registering it in MAPS API
We can create a new
certificate by using keytool.exe, found
in bin directory
of JDK installation path (C:\Program Files\Java\jdk1.7.0_01\bin).
Steps
to get MD5 Key:
1. Go to your android location(C:\Documents and
Settings\Tara Roy\.android) where you have set your Work Space.
2. Copy "debug.keystore" & put this file in
C:\debug.keystore
3. Go 2 your command prompt(cmd)
4. Type CD C:\Documents and Settings\Tara Roy
5. Next Type like this in cmd. C:\> keytool -list -v
-keystore C:\debug.keystore
6. Put password ""android""
7. You will get like this...
9. Put Your MD5 Key( 28:89:52:AA:BD:53:01:90:32:F7:93:27:34:85:2F:AF
).
10. Register after giving your mail-id.
11. Success(Page will look like this)
Thank you for signing up for an Android Maps API key!
Your key is:
0uG1kA1mLxMHCVq8ArHf3eYNX8isA19dNZXSYHg
This key will work for all apps signed with your
certificate whose fingerprint is:
FC:7A:5D:8D:E2:83:E9:68:31:CF:06:50:57:5E:EC:ED
Here is a sample xml layout to get you started on your
way to mapping glory:
<com.google.android.maps.MapView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:apiKey="0uG1kA1mLxMHCVq8ArHf3eYNX8isA19dNZXSYHg"
/>
Creating Application
Next: Create a new Android Project and provide the
details as below,….
Click Finish and the
project is created. Create a Run Configuration for the project to launch an AVD
targeted to Google APIs.
Try running the project
with the specified configuration and it should show something like:
Before
you can start using MapView control from Google APIs, you need to add the
Google Maps External Library (com.google.android.map) to the library. For adding a library to the project use uses-library tag. This tag needs to be added to AndroidManifest.xml. Apart from the library, you need to add
relevant permissions as well. For adding permissions, we use uses-permission tag. For our application, we will add the
following permissions:
·
android.permission.ACCESS_COARSE_LOCATION: Allows application to access coarse location
(Cell ID, Wi-Fi etc.)
·
android.permission.ACCESS_FINE_LOCATION: Allows application to access GPS location.
·
android.permission.INTERNET: Allows application to open network sockets.
AndroidManifest.xml will Look Like This:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.VertexVerveInc.GPSLocator"
android:versionCode="1"
android:versionName="1.0">
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
<uses-library android:name="com.google.android.maps" />
<activity android:name=".GPSLocatorActivity"
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>
Add MapView control to main.xml under res/layout.
The resultant code should look like:
<?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"
>
<com.google.android.maps.MapView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/present_mapview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:clickable="true"
android:enabled="true"
android:apiKey="0uG1kA1mLxMHCVq8ArHf3eYNX8isA19dNZXSYHg"
/>
</LinearLayout>
In order to display Google Map view, we
need to update our Activity class (GPSLocatorActivity).
This class should extend MapActivity class in
place of Activity class. We also need to importcom.google.android.maps.MapActivity
package to
support MapActivity class. We also need to overrideisRouteDisplayed method of MapActivity class. This
is fairly easy, just return false from the
method. After all these modifications, GPSLocatorActivity.java should
look like:
import com.google.android.maps.MapActivity;
import android.os.Bundle;
public class GPSLocatorActivity extends MapActivity
{
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
@Override
protected boolean isRouteDisplayed() {
return false;
}
}
Out
put will look like this:
We can select, if we want to show Satellite, Traffic or
Street view in maps. This is simply achieved by calling setSatellite,setStreetView and setTraffic methods.
Another thing to do before we move further is zoom the map a bit. Why? Because
the map view shown in the above output doesn't serve any purpose. In order to
set zoom level of Map, we need an instance of MapController and we can
call its setZoom method. So, let's update the onCreate method ofGPSLocatorActivity class to
incorporate all these changes.
mapView = (MapView) findViewById(R.id.mapView);
mapView.setStreetView(true);
mapView.setBuiltInZoomControls(true);
mapController = mapView.getController();
mapController.setZoom(16);
Android provides location based services through LocationManager (package
android.Location) class. This class provides periodical updates
about the location of the device. In order to user LocationManager, we need to get a reference of LocationManager class by calling getSystemService method.
Later on, we need to register for location updates by calling requestLocationUpdates method.
We need to create a class implementing abstract LocationListener class. This
class will be registered with Location Manager to receive updates of location.
We need to override all four methods of this class, namelyonLocationChanged, onProviderDisabled/Enabled,
and onStatusChanged. As
we are just interested in getting location updates, we will modify the code of onLocationChanged to
navigate to the new location received in the map view. This is achieved by
calling animateTo method
of MapController.
The Coding is changed and it will look like this:
public void onCreate(Bundle savedInstanceState) {
...
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
locationListener = new GPSLocationListener();
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
0,
0,
locationListener);
...
}
private class GPSLocationListener implements LocationListener
{
@Override
public void onLocationChanged(Location location) {
if (location != null) {
GeoPoint point = new GeoPoint(
(int) (location.getLatitude() * 1E6),
(int) (location.getLongitude() * 1E6));
Toast.makeText(getBaseContext(),
"Latitude: " + location.getLatitude() +
" Longitude: " + location.getLongitude(),
Toast.LENGTH_SHORT).show();
mapController.animateTo(point);
mapController.setZoom(16);
mapView.invalidate();
}
}
...
}
The Out put will look like this:
We can find information about an address if
we know its latitude and longitude. For this purpose, we use Geocoderclass
and the process is known as Geocoding. We will call getFromLocation method
of the class and will pass the point as a parameter. This method returns a List
of Address which contains information about address of the specified
location. We can combine the information to find the complete information about
the point. For this purpose, we will add a method
ConvertPointToLocation to GPSLocationListener class. ConvertPointToLocation returns
astring object containing address of the location.
Code will Look Like This:
class GPSLocationListener implements LocationListener {
@Override
public void onLocationChanged(Location
location) {
if (location != null) {
...
String address =
ConvertPointToLocation(point);
Toast.makeText(getBaseContext(), address,
Toast.LENGTH_SHORT).show();
...
}
}
public String ConvertPointToLocation(GeoPoint
point) {
String address = "";
Geocoder geoCoder = new Geocoder(
getBaseContext(), Locale.getDefault());
try {
List<Address> addresses =
geoCoder.getFromLocation(
point.getLatitudeE6() / 1E6,
point.getLongitudeE6() / 1E6, 1);
if (addresses.size() > 0) {
for (int index = 0;
index <
addresses.get(0).getMaxAddressLineIndex(); index++)
address += addresses.get(0).getAddressLine(index)
+ " ";
}
}
catch (IOException e) {
e.printStackTrace();
}
return address;
}
A lot many times, we want to add a marker (image) to the
location because the small circle (shown in maps by default) is sometimes
useless. In order to add a marker, add a drawable resource to the project. We
can import any image (which we want to use) to our project (simple drag and
drop also works). Add the image to res/drawable folder.
In order to add a location marker to the map, we need to
create a class which extends Overlay (com.google.android.maps
package) class. We need to override draw method
of the class and do some custom painting. The MapOverlay class looks
like:
class
GPSLocationListener implements LocationListener
{
@Override
public void
onLocationChanged(Location location) {
...
mapController.animateTo(point);
mapController.setZoom(16);
// add marker
MapOverlay
mapOverlay = new MapOverlay();
mapOverlay.setPointToDraw(point);
List<Overlay> listOfOverlays = mapView.getOverlays();
listOfOverlays.clear();
listOfOverlays.add(mapOverlay);
String
address = ConvertPointToLocation(point);
Toast.makeText(getBaseContext(), address, Toast.LENGTH_SHORT).show();
...
}
class MapOverlay extends Overlay
{
private GeoPoint
pointToDraw;
public void
setPointToDraw(GeoPoint point) {
pointToDraw =
point;
}
public GeoPoint
getPointToDraw() {
return
pointToDraw;
}
@Override
public boolean
draw(Canvas canvas, MapView mapView, boolean shadow, long when) {
super.draw(canvas, mapView, shadow);
// convert
point to pixels
Point screenPts
= new Point();
mapView.getProjection().toPixels(pointToDraw, screenPts);
// add marker
Bitmap bmp =
BitmapFactory.decodeResource(getResources(), R.drawable.red);
canvas.drawBitmap(bmp, screenPts.x, screenPts.y - 24, null);
return true;
}
}
