GeoFire for Android β Realtime location queries with Firebase
GeoFire is an open-source library for Android that allows you to store and query a set of keys based on their geographic location.
At its heart, GeoFire simply stores locations with string keys. Its main benefit however, is the possibility of querying keys within a given geographic area - all in realtime.
GeoFire uses the Firebase Realtime Database for data storage, allowing query results to be updated in realtime as they change. GeoFire selectively loads only the data near certain locations, keeping your applications light and responsive, even with extremely large datasets.
GeoFire clients are also available for other languages:
Integrating GeoFire with your data
GeoFire is designed as a lightweight add-on to the Firebase Realtime Database. However, to keep things simple, GeoFire stores data in its own format and its own location within your Firebase database. This allows your existing data format and security rules to remain unchanged and for you to add GeoFire as an easy solution for geo queries without modifying your existing data.
Example Usage
Assume you are building an app to rate bars and you store all information for a
bar, e.g. name, business hours and price range, at /bars/<bar-id>
. Later, you
want to add the possibility for users to search for bars in their vicinity. This
is where GeoFire comes in. You can store the location for each bar using
GeoFire, using the bar IDs as GeoFire keys. GeoFire then allows you to easily
query which bar IDs (the keys) are nearby. To display any additional information
about the bars, you can load the information for each bar returned by the query
at /bars/<bar-id>
.
Including GeoFire in your Android project
In order to use GeoFire in your project, you need to add the Firebase Android SDK. After that you can include GeoFire with one of the choices below.
Add a dependency for GeoFire to your app's build.gradle
file.
dependencies {
// Full GeoFire library for Realtime Database users
implementation 'com.firebase:geofire-android:3.2.0'
// GeoFire utililty functions for Cloud Firestore users who
// want to implement their own geo solution, see:
// https://firebase.google.com/docs/firestore/solutions/geoqueries
implementation 'com.firebase:geofire-android-common:3.2.0'
}
Usage
There are two ways to use GeoFire:
- GeoFire - an end-to-end solution for adding simple geo queries to apps using Firebase Realtime Database.
- GeoFireUtils - a set of utilities that make it simple to build a geo query solution for any app, such as those using Cloud Firestore.
GeoFire
A GeoFire
object is used to read and write geo location data to your Firebase
database and to create queries. To create a new GeoFire
instance you need to attach it to a Firebase database
reference.
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("path/to/geofire");
GeoFire geoFire = new GeoFire(ref);
Note that you can point your reference to anywhere in your Firebase database, but don't forget to setup security rules for GeoFire.
Setting location data
In GeoFire you can set and query locations by string keys. To set a location for
a key simply call the setLocation
method. The method is passed a key
as a string and the location as a GeoLocation
object containing the location's latitude and longitude:
geoFire.setLocation("firebase-hq", new GeoLocation(37.7853889, -122.4056973));
To check if a write was successfully saved on the server, you can add a
GeoFire.CompletionListener
to the setLocation
call:
geoFire.setLocation("firebase-hq", new GeoLocation(37.7853889, -122.4056973), new GeoFire.CompletionListener() {
@Override
public void onComplete(String key, FirebaseError error) {
if (error != null) {
System.err.println("There was an error saving the location to GeoFire: " + error);
} else {
System.out.println("Location saved on server successfully!");
}
}
});
To remove a location and delete it from the database simply pass the location's key to removeLocation
:
geoFire.removeLocation("firebase-hq");
Retrieving a location
Retrieving a location for a single key in GeoFire happens with callbacks:
geoFire.getLocation("firebase-hq", new LocationCallback() {
@Override
public void onLocationResult(String key, GeoLocation location) {
if (location != null) {
System.out.println(String.format("The location for key %s is [%f,%f]", key, location.latitude, location.longitude));
} else {
System.out.println(String.format("There is no location for key %s in GeoFire", key));
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
System.err.println("There was an error getting the GeoFire location: " + databaseError);
}
});
Geo Queries
GeoFire allows you to query all keys within a geographic area using GeoQuery
objects. As the locations for keys change, the query is updated in realtime and fires events
letting you know if any relevant keys have moved. GeoQuery
parameters can be updated
later to change the size and center of the queried area.
// creates a new query around [37.7832, -122.4056] with a radius of 0.6 kilometers
GeoQuery geoQuery = geoFire.queryAtLocation(new GeoLocation(37.7832, -122.4056), 0.6);
Receiving events for geo queries
Key Events
There are five kinds of "key" events that can occur with a geo query:
- Key Entered: The location of a key now matches the query criteria.
- Key Exited: The location of a key no longer matches the query criteria.
- Key Moved: The location of a key changed but the location still matches the query criteria.
- Query Ready: All current data has been loaded from the server and all initial events have been fired.
- Query Error: There was an error while performing this query, e.g. a violation of security rules.
Key entered events will be fired for all keys initially matching the query as well as any time afterwards that a key enters the query. Key moved and key exited events are guaranteed to be preceded by a key entered event.
Sometimes you want to know when the data for all the initial keys has been loaded from the server and the corresponding events for those keys have been fired. For example, you may want to hide a loading animation after your data has fully loaded. This is what the "ready" event is used for.
Note that locations might change while initially loading the data and key moved and key exited events might therefore still occur before the ready event is fired.
When the query criteria is updated, the existing locations are re-queried and the ready event is fired again once all events for the updated query have been fired. This includes key exited events for keys that no longer match the query.
To listen for events you must add a GeoQueryEventListener
to the GeoQuery
:
geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {
@Override
public void onKeyEntered(String key, GeoLocation location) {
System.out.println(String.format("Key %s entered the search area at [%f,%f]", key, location.latitude, location.longitude));
}
@Override
public void onKeyExited(String key) {
System.out.println(String.format("Key %s is no longer in the search area", key));
}
@Override
public void onKeyMoved(String key, GeoLocation location) {
System.out.println(String.format("Key %s moved within the search area to [%f,%f]", key, location.latitude, location.longitude));
}
@Override
public void onGeoQueryReady() {
System.out.println("All initial data has been loaded and events have been fired!");
}
@Override
public void onGeoQueryError(DatabaseError error) {
System.err.println("There was an error with this query: " + error);
}
});
You can call either removeGeoQueryEventListener
to remove a
single event listener or removeAllListeners
to remove all event listeners
for a GeoQuery
.
Data Events
If you are storing model data and geo data in the same database location, you may
want access to the DataSnapshot
as part of geo events. In this case, use a
GeoQueryDataEventListener
rather than a key listener.
These "data event" listeners have all of the same events as the key listeners with one additional event type:
- Data Changed: the underlying
DataSnapshot
has changed. Every "data moved" event is followed by a data changed event but you can also get change events without a move if the data changed does not affect the location.
Adding a data event listener is similar to adding a key event listener:
geoQuery.addGeoQueryDataEventListener(new GeoQueryDataEventListener() {
@Override
public void onDataEntered(DataSnapshot dataSnapshot, GeoLocation location) {
// ...
}
@Override
public void onDataExited(DataSnapshot dataSnapshot) {
// ...
}
@Override
public void onDataMoved(DataSnapshot dataSnapshot, GeoLocation location) {
// ...
}
@Override
public void onDataChanged(DataSnapshot dataSnapshot, GeoLocation location) {
// ...
}
@Override
public void onGeoQueryReady() {
// ...
}
@Override
public void onGeoQueryError(DatabaseError error) {
// ...
}
});
Updating the query criteria
The GeoQuery
search area can be changed with setCenter
and setRadius
. Key
exited and key entered events will be fired for keys moving in and out of
the old and new search area, respectively. No key moved events will be
fired; however, key moved events might occur independently.
Updating the search area can be helpful in cases such as when you need to update the query to the new visible map area after a user scrolls.
GeoFireUtils
The geofire-android-common
library provides the GeoFireUtils
class which contains utilities for working with geohashes but has no dependency on or integration with a specific database. The GeoFireUtils
class contains the following utility methods:
String getGeoHashForLocation(@NonNull GeoLocation location)
- compute the geohash string for a given (lat,lng) par with default precision.String getGeoHashForLocation(@NonNull GeoLocation location, int precision)
- compute the geohash string for a given (lat, lng) pair with custom precision.double getDistanceBetween(@NonNull GeoLocation a, @NonNull GeoLocation b)
- compute the distance, in kilometers, between two locations.List<GeoQueryBounds> getGeoHashQueryBounds(@NonNull GeoLocation location, double radius)
- given a center point and a radius distance, compute a set of query bounds that can be joined to find all points within the radius distance of the center.
For a detailed guide on how to use these utilities to add geo querying capabilities to your Cloud Firestore app, see: https://firebase.google.com/docs/firestore/solutions/geoqueries
Publishing
Versioning
We use SemVer in this project.
When you bump a version, be sure to update:
Credentials
The library is published to Maven Central by the firebase-sonatype account, Googlers can find the password for this account in Valentine
GPG Key
You will need to create a private GPG keyring on your machine, if you don't have one do the following steps:
- Run
gpg --full-generate-key
- Choose
RSA and RSA
for the key type - Use
4096
for the key size - Use
0
for the expiration (never) - Use any name, email address, and password
This creates your key in ~/.gnupg/openpgp-revocs.d/
with .rev
format. The last 8 characters
before the .rev
extension are your Key ID.
To export the key, run:
gpg --export-secret-keys -o $HOME/sonatype.gpg
Finally upload your key to the keyserver:
gpg --keyserver hkp://keys.openpgp.org --send-keys <YOUR KEY ID>
Local Properties
Open your $HOME/.gradle/gradle.properties
file at and fill in the values:
signing.keyId=<KEY ID>
signing.password=<PASSWORD YOU CHOSE>
signing.secretKeyRingFile=<FULL PATH TO YOUR GPG FILE>
mavenCentralRepositoryUsername=firebase-sonatype
mavenCentralRepositoryPassword=<PASSWORD FROM VALENTINE>
Publish
To publish, run:
./gradlew publish
Release
Follow the instructions here:
- Navigate to https://oss.sonatype.org/ and Log In
- On the left side menu, click Staging Repositories (under Build Promotion) and look for the
com.firebase
repo - You should see it with the
Open
status. Click Close and wait a few minutes (you can check status by clicking Refresh) - Once the status changes to
Closed
, click Release