1. CIS 470 Mobile App Development
Lecture 13
Wenbing Zhao
Department of Electrical Engineering and Computer Science
Cleveland State University
4/10/2019
CIS 470: Mobile App Development

2. Location-Based Services
Displaying Google Maps in your Android application
Displaying zoom controls on the map
Switching between the different map views
Retrieving the address location touched on the map
Performing geocoding and reverse geocoding
Obtaining geographical data using GPS, Cell-ID, and WiFi triangulation
Monitoring for a location
4/10/2019
CIS 470: Mobile App Development

3. CIS 470: Mobile App Development
Displaying Maps
When creating an app, need to select “Google Maps Activity”. Create an app and name it LBS
4/10/2019
CIS 470: Mobile App Development

4. CIS 470: Mobile App Development
Displaying Maps
Also need to obtain the Maps API key (after you created your app)
To get a Google Maps key, open the google_maps_api.xml file that was created in your LBS project
Within this file is a link to create a new Google Maps key
Copy and paste the link into your browser and follow the instructions
Replace the YOUR_KEY_HERE placeholder in the google_maps_api.xml with your Google Maps key
<resources> <! TODO: Before you run your application, you need a Google Maps API key. To get one, follow this link, follow the directions and press "Create" at the end: Once you have your key (it starts with "AIza"), replace the "google_maps_key" string in this file > <string name="google_maps_key" templateMergeStrategy="preserve" translatable="false">AIzaSyCHapqQ2PtdWBdKwhHX8RmLlrkzaWb7rdE</string> </resources>
4/10/2019
CIS 470: Mobile App Development

5. CIS 470: Mobile App Development
Zoom Control
In activity_maps.xml, add maps:uiZoomControls=“true”
<fragment xmlns:android=" xmlns:map=" xmlns:tools=" android:name="com.google.android.gms.maps.SupportMapFragment" android:layout_width="match_parent" android:layout_height="match_parent" map:uiZoomControls="true" tools:context="com.wenbing.lbs.MapsActivity" />
4/10/2019
CIS 470: Mobile App Development

6. CIS 470: Mobile App Development
Changing Views
By default, Google Maps is displayed in map view. You can change to satellite view programmatically by setting the map type:
mMap.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
4/10/2019
CIS 470: Mobile App Development

7. Navigating to a Specific Location
Programmatically show the map around a specific location using moveCamera() method
public void onMapReady(GoogleMap googleMap) { mMap = googleMap; // Add a marker in Sydney and move the camera LatLng sydney = new LatLng(-34, 151); mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney")); mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney)); // mMap.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
4/10/2019
CIS 470: Mobile App Development

8. Getting the Location that was touched
To get the latitude and longitude of a point on the Google Map that was touched, you must set a onMapClickListener on mMap in onMapReady() method
mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() { @Override public void onMapClick(LatLng point) { Log.d("DEBUG","Map clicked [" + point.latitude + " / " + point.longitude + "]"); Geocoder geoCoder = new Geocoder(getBaseContext(), Locale.getDefault()); try { List<Address> addresses = geoCoder.getFromLocation(point.latitude,point.longitude,1); String add = ""; if (addresses.size() > 0) { for (int i=0; i<addresses.get(0).getMaxAddressLineIndex(); i++) add += addresses.get(0).getAddressLine(i) + "\n"; } Toast.makeText(getBaseContext(), add, Toast.LENGTH_SHORT).show(); } catch (IOException e) { e.printStackTrace(); } LatLng p = new LatLng(point.latitude, point.longitude); mMap.moveCamera(CameraUpdateFactory.newLatLng(p)); } });
4/10/2019
CIS 470: Mobile App Development

9. Geocoding and Reverse Geocoding
Knowing latitude and longitude of a location, you can find out its address using a process known as reverse geocoding
Google Maps in Android supports reverse geocoding via the Geocoder class
The Geocoder object converts the latitude and longitude into an address using the getFromLocation() method
4/10/2019
CIS 470: Mobile App Development

10. Geocoding and Reverse Geocoding
If you know the address of a location but want to know its latitude and longitude, you can do so via geocoding using getFromLocationName() method
Geocoder geoCoder = new Geocoder(getBaseContext(), Locale.getDefault());
try {
List<Address> addresses = geoCoder.getFromLocationName(
"empire state building", 5);
if (addresses.size() > 0) {
LatLng p = new LatLng((int) (addresses.get(0).getLatitude()),
(int) (addresses.get(0).getLongitude()));
mMap.moveCamera(CameraUpdateFactory.newLatLng(p)); }
} catch (IOException e) {
e.printStackTrace();
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CIS 470: Mobile App Development

11. CIS 470: Mobile App Development
Get Location Data
Three means:
GPS
Cell tower triangulation
WiFI
In Android, use LocationManager
Add permission in manifest
To simulate GPS data received by the Android emulator, you use the Location Controls tool on the right-hand side of the emulator
After starting the app, observe that the map on the emulator now animates to your current location. This indicates that the application has received the GPS data
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
4/10/2019
CIS 470: Mobile App Development

12. CIS 470: Mobile App Development
Get Location Data
import android.support.v4.app.FragmentActivity; import android.os.Bundle; import android.util.Log; import com.google.android.gms.maps.CameraUpdateFactory; import com.google.android.gms.maps.GoogleMap; import com.google.android.gms.maps.OnMapReadyCallback; import com.google.android.gms.maps.SupportMapFragment; import com.google.android.gms.maps.model.LatLng; import com.google.android.gms.maps.model.MarkerOptions; import android.location.Address; import android.location.Geocoder; import android.widget.Toast; import java.io.IOException; import java.util.Locale; import java.util.List; import android.support.v4.app.ActivityCompat; import android.content.pm.PackageManager; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; import android.content.Context;
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CIS 470: Mobile App Development

13. CIS 470: Mobile App Development
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback { final private int REQUEST_COURSE_ACCESS = 123; boolean permissionGranted = false; LocationManager lm; LocationListener locationListener; private GoogleMap mMap; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_maps); SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager() findFragmentById(R.id.map); mapFragment.getMapAsync(this); } @Override public void onMapReady(GoogleMap googleMap) { mMap = googleMap; lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE); locationListener = new MyLocationListener(); if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission( this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION}, REQUEST_COURSE_ACCESS); return; }else{ permissionGranted = true; }
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CIS 470: Mobile App Development

14. CIS 470: Mobile App Development
@Override public void onMapReady(GoogleMap googleMap) { // continue from previous slide
if(permissionGranted) { lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener); } // Add a marker in Sydney and move the camera LatLng sydney = new LatLng(-34, 151); mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney")); mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney)); mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() { @Override public void onMapClick(LatLng point) { Log.d("DEBUG","Map clicked [" + point.latitude + " / " + point.longitude + "]"); Geocoder geoCoder = new Geocoder(getBaseContext(), Locale.getDefault()); try { List<Address> addresses = geoCoder.getFromLocation(point.latitude,point.longitude,1); String add = ""; if (addresses.size() > 0) { for (int i=0; i<addresses.get(0).getMaxAddressLineIndex(); i++) add += addresses.get(0).getAddressLine(i) + "\n"; } Toast.makeText(getBaseContext(), add, Toast.LENGTH_SHORT).show(); } catch (IOException e) { e.printStackTrace(); } } }); }
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CIS 470: Mobile App Development

15. CIS 470: Mobile App Development
@Override public void onPause() { super.onPause(); //---remove the location listener if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission( this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION}, REQUEST_COURSE_ACCESS); return; }else{ permissionGranted = true; } if(permissionGranted) { lm.removeUpdates(locationListener); } } @Override public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) { switch (requestCode) { case REQUEST_COURSE_ACCESS: if (grantResults[0] == PackageManager.PERMISSION_GRANTED) { permissionGranted = true; } else { permissionGranted = false; } break; default: super.onRequestPermissionsResult(requestCode, permissions, grantResults); } }
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CIS 470: Mobile App Development

16. CIS 470: Mobile App Development
private class MyLocationListener implements LocationListener { public void onLocationChanged(Location loc) { if (loc != null) { Toast.makeText(getBaseContext(), "Location changed : Lat: " + loc.getLatitude() " Lng: " + loc.getLongitude(), Toast.LENGTH_SHORT).show(); LatLng p = new LatLng( (int) (loc.getLatitude()), (int) (loc.getLongitude())); mMap.moveCamera(CameraUpdateFactory.newLatLng(p)); mMap.animateCamera(CameraUpdateFactory.zoomTo(7)); } else { System.out.println("loc is null"); } Toast.makeText(getBaseContext(), "onLocation"+loc, Toast.LENGTH_SHORT).show(); } public void onProviderDisabled(String provider) { } public void onProviderEnabled(String provider) { } public void onStatusChanged(String provider, int status, Bundle extras) { } } }
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CIS 470: Mobile App Development

17. CIS 470: Mobile App Development
Monitoring a Location
Do something when the user (who carries the Android phone with the app) is getting close to a location using the addProximityAlert() method
import android.app.PendingIntent;
import android.content.Intent;
import android.net.Uri;
//---use the LocationManager class to obtain locations data---
lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
//---PendingIntent to launch activity if the user is within some locations---
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, new
Intent(android.content.Intent.ACTION_VIEW,
Uri.parse(" 0);
lm.addProximityAlert( , , 5, -1, pendingIntent);
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CIS 470: Mobile App Development

18. CIS 470: Mobile App Development
Homework #17
Refactor the demo app:
Add two buttons for the map view and satellite view
Add another button for displaying current location
When clicking a location on the map, add a marker and move the camera to that location
Add a EditText view and a button such that when you enter a valid address, the camera will move to that location
4/10/2019
CIS 470: Mobile App Development