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Android BLE beacon advertising library

Broadcast Bluetooth Low Energy beacons directly from Android 5.0 or later, on devices that support BLE peripheral mode. This library powers the Beacon Toy app and the UriIO client library for ephemeral URL beacons.

What this library is

An easy way for your app to broadcast Bluetooth beacons.

What this library isn't

A beacon scanning library. To scan for beacons in your app, use the Nearby API, or (for advanced needs) try OneBeacon.

Features

IMPORTANT! A minimum-priority notification allows the user to stop all currently running beacons, for the following reason. If your app crashes or the beacons service is killed and restarted, all saved active beacons will restart advertising. A device has a maximum number of concurrent BLE broadcasters (4 on Nexus 6; 8 on Galaxy S7, etc.). When this number is reached, new beacons will fail to start. It's best to make sure you stop() or delete() a beacon after you no longer need it, but the notification assures the user is in control.

Setup

  1. Add the library to your app module's build.gradle.

    dependencies {
   ...
   compile 'com.uriio:beacons-android:1.5.2'
}

  2. Initialize the library. Usually you would do this when onCreate() is called in either your Application, Activity, or Service. If you had any previously active beacons that you created and saved, they will resume. The beacon management is handled by the library's BleService, which monitors the Bluetooth state and stops / restarts beacons accordingly.

    Beacons.initialize(this);

Creating beacons

You can create and start new beacons with one-liners.

Eddystone-URL, Eddystone-UID, iBeacon

// starts an Eddystone-URL beacon ASAP
new EddystoneURL("https://github.com").start();

// a custom Beacon
new iBeacon(uuid, major, minor).start();

// a more sophisticated beacon
new EddystoneUID(myUID, AdvertiseSettings.ADVERTISE_MODE_BALANCED, AdvertiseSettings.ADVERTISE_TX_POWER_LOW)
   .start();

// a telemetry beacon that updates the data once every minute
new EddystoneTLM(60000).start()

After adding a beacon, it will begin to advertise immediately if Bluetooth is on (or when it gets enabled). Because starting up a beacon is an Android async operation, if there's an error, a broadcast is sent by the service. See the listening for events section for how to handle this.

All beacon constructors support extra arguments, to set their initial properties like Advertise mode, TX power, lock key, or name.

Beacon myUrlBeacon = new EddystoneURL(url, ...);
Beacon myUidBeacon = new EddystoneUID(namespaceInstance), ...;
Beacon myiBeacon = new iBeacon(uuid, major, minor, ...);

Eddystone EID

The library supports full production-ready EID beacons. The beacon's advertised EID will automatically update when needed, using scheduled Android system Alarms, so with zero battery impact.

An EID beacon first needs to be registered. For testing only, you can fake a registration and use that to provision an EID beacon. Much better, just use the built-in Eddystone-GATT service (see below) and use an external tool (like Beacon Tools) to register a new EID beacon. That will take care of all the ugly details.

fakeRegistration = EIDUtils.register(new LocalEIDResolver(), mTemporaryKeyPair.getPublicKey(),
      mTemporaryKeyPair.getPrivateKey(), rotationExponent);

// using the registration result we can now start an EID beacon
new EddystoneEID(registrationResult.getIdentityKey(), rotationExponent,
      registrationResult.getTimeOffset()).start();

Eddystone-GATT

An actual Eddystone-GATT configuration service can run on the local device, allowing a remote user to configure a new or existing Eddystone URL/UID/EID beacon.

The final configured beacon may be different than the initially configured one, because its type may change (e.g. it was an Eddystone-URL and it ends up an Eddystone-UID, etc.)

You receive the configured beacon in a callback after the owner disconnects. The beacon will already be enabled for advertising. If you provide an initial configurable beacon, the final beacon will also be automatically saved, if the original beacon was saved. If the final beacon is of a different type, the original beacon will be deleted, and its Lock Key, name, and other basic properties will be copied to the new beacon.

mGattServer = new EddystoneGattServer(new EddystoneGattServer.Listener() {
   @Override
   public void onGattFinished(EddystoneBase configuredBeacon) {
      if (null != configuredBeacon) {
         // take action - configured beacon is started at this point
         
         // the final beacon's saved state depends on the provided configurable beacon saved state
         // if you provided a non-saved beacon (or none at all), save here if desired
         configuredBeacon.save(true);
      }
      
      // mark object as disposable
      mGattServer = null;   // close() not needed here
   }
});

You can then start the GATT service, passing in an optional beacon as the configured beacon.

The provided beacon will become connectable, so most probably it will no longer advertise while someone is connected. At least on some devices, if another BLE advertiser starts while you are connected, the connection may be dropped.

// for the initial configured beacon, use an Eddystone-URL that advertises its own Web Bluetooth config URL
boolean success = mGattServer.start();

boolean success = mGattServer.start("https://some.custom.url");

// use a blank Eddystone-UID beacon as the configured beacon
boolean success = mGattServer.start(new EddystoneUID());

// make an existing beacon connectable and configurable. Note that this original
// beacon might end up DELETED if the final configured beacon is of a separate type.
boolean success = mGattServer.start(myExistingBeacon);

Every Eddystone beacon has its own Lock Key. To allow future re-configuration, and since the Proximity API also has a field for an Unlock Key, we can't just create a new Unlock Key each time a beacon is configured via GATT.

if (success) {
   // you should present the Unlock Key somehow to the user, since it's needed to connect to the beacon
   String hexUnlockKey = Util.binToHex(mGattServer.getBeacon().getLockKey(), ' ');
}

Don't forget to close the GATT service when it's no longer needed ("Cancel" button, activity/fragment closes, etc.)

mGattServer.close();  // ends GATT as if the owner finished config

You can attach a simple logging callback to the GATT instance, to display relevant events:

// call this before start() to log start-up errors
mGattServer.setLogger(new Loggable() {
   @Override
   public void log(String tag, final String message) {
      // log however you want (note: this method is not always invoked from the original thread)
      if(VERBOSE) Log.d(tag, message);
   }
});

Changing beacon state

A beacon can be in one of three states: Enabled, Paused, or Stopped.

beacon.start();    // active beacon, it runs when possible
beacon.pause();    // sets a beacon to paused state, e.g. active but not running
beacon.stop();     // stops advertising and removes a beacon from active list

Saving beacons

If you want a beacon to survive between service or app restarts, you should save it to persistent storage. The default save() method will also enable the beacon to advertise.

beacon.save();  // equivalent to: beacon.save(false); beacon.start();

beacon.save(false);  // saves the beacon but does not enable it

Editing beacons

For all beacons, you can update a beacon's TX power, broadcast frequency, name. Some beacons properties are immutable (example: EID identity key or clock offset). The general pattern to update one or more properties:

// note: the chained calls return an Editor, which doesn't always auto-cast to the actual subclass.
// to fix this, either use a local variable for edit() return type, or call first the set
// methods defined by the child subclass, and then from its parents.
beacon.edit()
   .setName("My awesome beacon!")
   .setAdvertiseMode(value)
   .apply();

Only if really needed (e.g. a new TX power, advertising mode, or beacon payload changes), the beacon will restart. Saving is automatic.

Deleting a beacon

Use this to permanently remove a beacon from the database.

beacon.delete();

Listing the beacons

Beacons.getActive() will return the list of enabled or paused beacons. Call beacon.getActiveState() to determine if a beacon is enabled or paused.

Saved beacons are stored in a private SQLite database, accesible only by your app (unless rooted, obviously). If a beacon is saved, it can be retrieved by its saved ID. Otherwise, when it's stopped (or the app somehow gets killed), the beacon will be gone forever.

To iterate over the stopped but saved beacons, use Beacons.getStopped() which returns a Cursor. While iterating over the cursor call Beacon.fromCursor() to create the specific beacon instance.

Listening for events

Because beacon lifecycle depends on a lot of factors (Bluetooth state and drivers mainly), they can start and stop at any time.

Your front-end app might not even have a running Activity when a beacon restarts due to a Service or Bluetooth restart, for instance.

To listen for events regarding beacons you have to register a broadcast receiver with a BleService.ACTION_BEACONS action filter.

It's your decision if you would like to use a global receiver that will be called when your Activity is stopped, or use dynamic broadcast receivers inside your code. Or both.

For dynamic receivers it's recommended to register using the LocalBroadcastManager from the appcompat-v7 library, so the receiver can't be called from other applications. Likewise, global receivers declared in your manifest should be marked with android:exported="false" (which is the default value unless you also declared an intent filter for it).

    @Override
    public void onReceive(Context context, Intent intent) {
        if (BleService.ACTION_BEACONS.equals(intent.getAction())) {
            // some events also contain a beacon ID, or error message / code
            switch (intent.getIntExtra(BleService.EXTRA_BEACON_EVENT, 0)) {
                case BleService.EVENT_ADVERTISER_ADDED:
                    // a new or stopped beacon entered active state
                    break;
                case BleService.EVENT_ADVERTISER_STARTED:
                    // a beacon started transmitting a new advertisement
                    break;
                case BleService.EVENT_ADVERTISER_STOPPED:
                    // a beacon was paused, stopped, or its advertiser will restart
                    break;
                case BleService.EVENT_ADVERTISER_FAILED:  // BLE failure
                    break;
                case BleService.EVENT_ADVERTISE_UNSUPPORTED:
                    // device doesn't support peripheral mode
                    break;
                case BleService.EVENT_START_FAILED:
                    // beacon refused to start for some reason, check its error details
                    break;
            }
        }
    }

Notification actions

When there is at least one beacon running, a persistent notification will be created, to allow the service to run as a foreground service (less likely to be killed), and also as a heads-up to the user that their device is an active beacon transmitter.

To provide a hook to the action to be taken when the notification is tapped, do the following:

  1. Create (or reuse one) a BroadcastReceiver and add it to your AndroidManifest.xml

  2. Update AndroidManifest.xml with a meta-data that points to this receiver, like below:

       <!-- Replace with your receiver. Make sure it remains non-exported -->
   <receiver android:name=".MyReceiver" android:exported="false"/>
   
   <!-- REPLACE <my-package-name> and MyReceiver with actual (sub)package and class name -->
   <meta-data android:name="com.uriio.receiver" android:value="<my-package-name>.MyReceiver" />

  3. Respond to the user tapping the notification content, in your receiver:

        @Override
    public void onReceive(Context context, Intent intent) {
        if (BleService.ACTION_NOTIFICATION_CONTENT.equals(intent.getAction())) {
            // this example starts your own Activity
            context.startActivity(new Intent(context, MainActivity.class)
                    .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_SINGLE_TOP)
                    .putExtra(MainActivity.EXTRA_BEACONS_NOTIFICATION, true));
        }
    }

Building the library

Clone the repo and build the library:

> git clone https://github.com/uriio/beacons-android
> cd beacons-android
> gradlew build

For a painless process, make sure your Android SDK and environment are correctly set-up.

Known supported devices

Non-exhaustive list of devices where BLE advertising is known to work. Newer models of these may or may not support BLE advertising, as it's up to the manufacturer, chipset, and drivers. [Brackets] indicate variations besides the base model.