Android Geocoding – Showing User Input Location on Google Map

Geocoding is the process of transforming a street address or other description of a location into a (latitude, longitude) coordinate.

This application facilitates to find a location in the Google Map by entering location in a textview. On clicking the find button, the application contacts geocoding web service via Geocoder api with the user input location string. The list of addresses returned from the webservice will contain information such as latitude, longitude, address details etc. These information(latitude and longitude) will be used to plot the location in Google Map.

This application is developed in Eclipse ( 4.2.0 ) withADT plugin ( 20.0.3 ) and Android SDK (R20.0.3).

Update : An upgraded version of this application with Google Map Android API V2 is available in the article titled “Android Geocoding – Showing User Input Location on Google Map Android API V2“.

1. Create a new Android application project namely “LocationGeocoding”

Figure 1 : Create a new Android Application Project

2. Design application launcher icon

Figure 2 : Design application launcher icon

3. Create a blank activity to define the class MainActivity

Figure 3 : Create a blank activity

4. Enter MainActivity details

Figure 4 : Enter MainActivity details

5. Delete Android’s Support Library from this project

By default Eclipse ( 4.2.0) adds Android Support Library to  Android application project. For this application, we don’t need to use this support library. So the library file libs/android-support-v4.jar may be removed manually via ProjectExplorer by simply right click on the file and then clicking the menu item “delete”.

6. Obtain Google Map Key

Google’s Map Key for the Android application will be available here.

The map key obtained has to be entered as the value of the attribute android:apiKey in the layout file res/layout/activity_main.

7. Create a new folder namely drawable under the folder “res”

8. Download the given below image file namely “marker.png” to the folder “res/drawable”

Google Map - Marker Image 1.83 KB

Download Marker Image

9. Update the file res/values/strings.xml

<resources>
    <string name="app_name">Geocoding Demo</string>
    <string name="hello_world">Hello world!</string>
    <string name="menu_settings">Settings</string>
    <string name="title_activity_main">Geocoding Demo</string>
    <string name="str_btn_find">Find</string>
    <string name="hnt_et_location">Enter location</string>
</resources>

10. Update the file res/layout/activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/btn_find"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/str_btn_find"
            android:layout_alignParentRight="true" />

        <EditText
            android:id="@+id/et_location"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:inputType="text"
            android:hint="@string/hnt_et_location"
            android:layout_toLeftOf="@id/btn_find" />

    </RelativeLayout>

    <com.google.android.maps.MapView
        android:id="@+id/map_view"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:apiKey="0u7AJChI1NV8vCpj21C0Cq8YnNMrB6YMgigu0GA"
        android:clickable="true" />

</LinearLayout>

Note : Replace the value of android:apiKey (Line 33)  with the Google Map Key obtained in Step 6

11. Create a class namely LocationOverlay in the file src/in/wptrafficanalyzer/locationgeocoding/LocationOverlay.java

package in.wptrafficanalyzer.locationgeocoding;

import java.util.ArrayList;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.widget.Toast;

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

public class LocationOverlay extends ItemizedOverlay<OverlayItem> {

    private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();
    private Context mContext;

    public LocationOverlay(Drawable defaultMarker,Context context) {
        super(boundCenterBottom(defaultMarker));
        mContext = context;

    }

    // Executed, when populate() method is called
    @Override
    protected OverlayItem createItem(int arg0) {
        return mOverlays.get(arg0);
    }

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

    public void addOverlay(OverlayItem overlay){
        mOverlays.add(overlay);
        populate(); // Invokes the method createItem()
    }

    @Override
    protected boolean onTap(int arg0) {
        // Getting the tapped item
        OverlayItem item = getItem(arg0);

        Toast.makeText(mContext, item.getSnippet(), Toast.LENGTH_SHORT).show();
        return true;
    }
}

12. Update the class MainActivity in the file src/in/wptrafficanalyzer/locationgeocoding/MainActivity.java

package in.wptrafficanalyzer.locationgeocoding;

import java.io.IOException;
import java.util.List;

import android.graphics.drawable.Drawable;
import android.location.Address;
import android.location.Geocoder;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

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 MainActivity extends MapActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Getting reference to btn_find of the layout activity_main
        Button btn_find = (Button) findViewById(R.id.btn_find);

        // Defining button click event listener for the find button
        OnClickListener findClickListener = new OnClickListener() {
            @Override
            public void onClick(View v) {
                // Getting reference to EditText to get the user input location
                EditText etLocation = (EditText) findViewById(R.id.et_location);

                // Getting user input location
                String location = etLocation.getText().toString();

                if(location!=null && !location.equals("")){
                    new GeocoderTask().execute(location);
                }
            }
        };

        // Setting button click event listener for the find button
        btn_find.setOnClickListener(findClickListener);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    protected boolean isRouteDisplayed() {
        // TODO Auto-generated method stub
        return false;
    }

    // An AsyncTask class for accessing the GeoCoding Web Service
    private class GeocoderTask extends AsyncTask<String, Void, List<Address>>{

        @Override
        protected List<Address> doInBackground(String... locationName) {
            // Creating an instance of Geocoder class
            Geocoder geocoder = new Geocoder(getBaseContext());
            List<Address> addresses = null;

            try {
                // Getting a maximum of 3 Address that matches the input text
                addresses = geocoder.getFromLocationName(locationName[0], 3);
            } catch (IOException e) {
                e.printStackTrace();
            }
            return addresses;
        }

        @Override
        protected void onPostExecute(List<Address> addresses) {

            // Getting Reference to MapView of the layout activity_main
            MapView mapView = (MapView) findViewById(R.id.map_view);

            // Setting ZoomControls
            mapView.setBuiltInZoomControls(true);

            // Getting MapController for the MapView
            MapController mc = mapView.getController();

            // Getting Drawable object corresponding to a resource image
            Drawable drawable = getResources().getDrawable(R.drawable.marker);

            // Getting Overlays of the map
            List<Overlay> overlays = mapView.getOverlays();

            // Creating an ItemizedOverlay
            LocationOverlay locationOverlay = new LocationOverlay(drawable,getBaseContext());

            // Clearing the overlays
            overlays.clear();

            if(addresses==null || addresses.size()==0){
                Toast.makeText(getBaseContext(), "No Location found", Toast.LENGTH_SHORT).show();

                // Redraws the map to clear the overlays
                mapView.invalidate();
            }

            // Adding Markers on Google Map for each matching address
            for(int i=0;i<addresses.size();i++){

                Address address = (Address) addresses.get(i);

                // Creating an instance of GeoPoint, to display in Google Map
                GeoPoint p = new GeoPoint(
                                            (int)(address.getLatitude()*1E6),
                                            (int)(address.getLongitude()*1E6)
                                        );

                String addressText = String.format("%s, %s",
                        address.getMaxAddressLineIndex() > 0 ? address.getAddressLine(0) : "",
                        address.getCountryName());

                // Creating an OverlayItem to mark the point
                OverlayItem overlayItem = new OverlayItem(p, "Location",addressText);

                // Adding the OverlayItem in the LocationOverlay
                locationOverlay.addOverlay(overlayItem);

                // Adding locationOverlay to the overlay
                overlays.add(locationOverlay);

                // Locate the first location
                if(i==0)
                    mc.animateTo(p);
            }

            // Redraws the map
            mapView.invalidate();
        }
    }
}

13. Update the file AndroidManifest.xml

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

    <uses-sdk
        android:minSdkVersion="4"
        android:targetSdkVersion="15" />

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

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

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

        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

14. Screenshot of the application

Figure 5 : Displaying the locations returned from Geocoding Web Service in Google APIs Emulator ( API Level 4 )

15. Download

Android Geocoding - Showing User Input Location on Google Map 149.35 KB

Download Full Source Code

16. Reference

http://developer.android.com/guide/index.html

How to hire me?

I am George Mathew, working as software architect and Android app developer at wptrafficanalyzer.in

You can hire me on hourly basis or on project basis for Android applications development.

For hiring me, please mail your requirements to info@wptrafficanalyzer.in.

My other blogs
store4js.blogspot.com

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Tags: ASyncTask, Geocoder, Geocoding, Google Map, ItemizedOverlay, map, MapActivity, OverlayItem