Building Apps with Location & Maps

Apps that use location services must request location permissions. Android offers two location permissions:ACCESS_COARSE_LOCATION and ACCESS_FINE_LOCATION. 

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.google.android.gms.location.sample.basiclocationsample" >
  
  <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
</manifest>

To connect, call connect() from the activity's onStart() method. To disconnect, call disconnect() from the activity's onStop() method. The following snippet shows an example of how to use both of these methods.

protected void onStart() {
    mGoogleApiClient.connect();
    super.onStart();
}

protected void onStop() {
    mGoogleApiClient.disconnect();
    super.onStop();
}

》  if your app helps the user find their way while walking or driving, or if your app tracks the location of assets, it needs to get the location of the device at regular intervals

 Net ,WiFi and GPS (Global Positioning System) to locate the position.

Performance hint: If your app accesses the network or does other long-running work after receiving a location update, adjust the fastest interval to a slower value. This adjustment prevents your app from receiving updates it can't use. Once the long-running work is done, set the fastest interval back to a fast value. 

protected void createLocationRequest() {
    LocationRequest mLocationRequest = new LocationRequest();
    mLocationRequest.setInterval(10000);
    mLocationRequest.setFastestInterval(5000);
    mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
}

》  onSaveInstanceState ( Bundle savedInstanceState )与

public void onSaveInstanceState(Bundle savedInstanceState) {
    savedInstanceState.putBoolean(REQUESTING_LOCATION_UPDATES_KEY,
            mRequestingLocationUpdates);
    savedInstanceState.putParcelable(LOCATION_KEY, mCurrentLocation);
    savedInstanceState.putString(LAST_UPDATED_TIME_STRING_KEY, mLastUpdateTime);
    super.onSaveInstanceState(savedInstanceState);
}

@Override
public void onCreate(Bundle savedInstanceState) {
    ...
    updateValuesFromBundle(savedInstanceState);
}

private void updateValuesFromBundle(Bundle savedInstanceState) {
    if (savedInstanceState != null) {
        // Update the value of mRequestingLocationUpdates from the Bundle, and
        // make sure that the Start Updates and Stop Updates buttons are
        // correctly enabled or disabled.
        if (savedInstanceState.keySet().contains(REQUESTING_LOCATION_UPDATES_KEY)) {
            mRequestingLocationUpdates = savedInstanceState.getBoolean(
                    REQUESTING_LOCATION_UPDATES_KEY);
            setButtonsEnabledState();
        }

        // Update the value of mCurrentLocation from the Bundle and update the
        // UI to show the correct latitude and longitude.
        if (savedInstanceState.keySet().contains(LOCATION_KEY)) {
            // Since LOCATION_KEY was found in the Bundle, we can be sure that
            // mCurrentLocationis not null.
            mCurrentLocation = savedInstanceState.getParcelable(LOCATION_KEY);
        }

        // Update the value of mLastUpdateTime from the Bundle and update the UI.
        if (savedInstanceState.keySet().contains(LAST_UPDATED_TIME_STRING_KEY)) {
            mLastUpdateTime = savedInstanceState.getString(
                    LAST_UPDATED_TIME_STRING_KEY);
        }
        updateUI();
    }
}

Note:  For a more persistent storage, you can store the user's preferences in your app's  SharedPreferences . Set the shared preference in your activity's  onPause()  method, and retrieve the preference in  onResume() . 

》how to start the intent service:

public class MainActivity extends ActionBarActivity implements
        ConnectionCallbacks, OnConnectionFailedListener {

    protected Location mLastLocation;
    private AddressResultReceiver mResultReceiver;
    ...

    protected void startIntentService() {
        Intent intent = new Intent(this, FetchAddressIntentService.class);
        intent.putExtra(Constants.RECEIVER, mResultReceiver);
        intent.putExtra(Constants.LOCATION_DATA_EXTRA, mLastLocation);
        startService(intent);
    }
}

public class GeofenceTransitionsIntentService extends IntentService {
   ...
    protected void onHandleIntent(Intent intent) {
        GeofencingEvent geofencingEvent = GeofencingEvent.fromIntent(intent);
        if (geofencingEvent.hasError()) {
            String errorMessage = GeofenceErrorMessages.getErrorString(this,
                    geofencingEvent.getErrorCode());
            Log.e(TAG, errorMessage);
            return;
        }

        // Get the transition type.
        int geofenceTransition = geofencingEvent.getGeofenceTransition();

        // Test that the reported transition was of interest.
        if (geofenceTransition == Geofence.GEOFENCE_TRANSITION_ENTER ||
                geofenceTransition == Geofence.GEOFENCE_TRANSITION_EXIT) {

            // Get the geofences that were triggered. A single event can trigger
            // multiple geofences.
            List triggeringGeofences = geofencingEvent.getTriggeringGeofences();

            // Get the transition details as a String.
            String geofenceTransitionDetails = getGeofenceTransitionDetails(
                    this,
                    geofenceTransition,
                    triggeringGeofences
            );

            // Send notification and log the transition details.
            sendNotification(geofenceTransitionDetails);
            Log.i(TAG, geofenceTransitionDetails);
        } else {
            // Log the error.
            Log.e(TAG, getString(R.string.geofence_transition_invalid_type,
                    geofenceTransition));
        }
    }

》 You can use the following techniques to optimize power consumption in your apps that use geofencing:

• Set the notification responsiveness to a higher value. Doing so improves power consumption by increasing the latency of geofence alerts. For example, if you set a responsiveness value of five minutes your app only checks for an entrance or exit alert once every five minutes. Setting lower values does not necessarily mean that users will be notified within that time period (for example, if you set a value of 5 seconds it may take a bit longer than that to receive the alert).

• Use a larger geofence radius for locations where a user spends a significant amount of time, such as home or work. While a larger radius doesn't directly reduce power consumption, it reduces the frequency at which the app checks for entrance or exit, effectively lowering overall power consumption.

For best results, the minimium radius of the geofence should be set between 100 - 150 meters. When Wi-Fi is available location accuracy is usually between 20 - 50 meters. When indoor location is available, the accuracy range can be as small as 5 meters. Unless you know indoor location is available inside the geofence, assume that Wi-Fi location accuracy is about 50 meters.

When Wi-Fi location is not available (for example, when you are driving in rural areas) the location accuracy degrades. The accuracy range can be as large as several hundred meters to several kilometers. In cases like this, you should create geofences using a larger radius.

》Allow your users to explore the world with rich maps provided by Google. Identify locations with custom markers, augment the map data with image overlays, embed one or more maps as fragments, and much more.

The new Maps offer exciting features such as 3D maps; indoor, satellite, terrain, and hybrid maps; vector-based tiles for efficient caching and drawing; animated transitions; and much more.