RxAndroidBle is a powerful painkiller for Android's Bluetooth Low Energy headaches. It is backed by RxJava, implementing complicated APIs as handy reactive observables. The library does for you:
- Fancy asynchronous operations support (read, write, notifications)
- Threading management in order to meet Android contracts
- Connection and operation error handling
For support head to StackOverflow #rxandroidble
Read the official announcement at Polidea Blog.
It's your job to maintain single instance of the client. You can use singleton, scoped Dagger component or whatever else you want.
RxBleClient rxBleClient = RxBleClient.create(context);The library does not handle managing the state of the BluetoothAdapter.
Direct managing of the state is not recommended as it violates the application user's right to manage the state of their phone. See Javadoc of BluetoothAdapter.enable() method.
It is the user's responsibility to inform why the application needs Bluetooth to be turned on and for ask the application's user consent.
It is possible to show a native activity for turning the Bluetooth on by calling:
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
int REQUEST_ENABLE_BT = 1;
context.startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);Scanning devices in the area is simple as that:
Subscription scanSubscription = rxBleClient.scanBleDevices(
new ScanSettings.Builder()
// .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY) // change if needed
// .setCallbackType(ScanSettings.CALLBACK_TYPE_ALL_MATCHES) // change if needed
.build()
// add filters if needed
)
.subscribe(
scanResult -> {
// Process scan result here.
},
throwable -> {
// Handle an error here.
}
);
// When done, just unsubscribe.
scanSubscription.unsubscribe();For devices with API <21 (before Lollipop) the scan API is emulated to get the same behaviour.
On Android it is not always trivial to determine if a particular BLE operation has a potential to succeed. i.e. to scan on Android 6.0 the device needs to have a BluetoothAdapter, the application needs to have a granted permission to use either ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION and Location Services needs to be turned on.
To be sure that the scan will work only when everything is ready you could use:
Subscription flowSubscription = rxBleClient.observeStateChanges()
.switchMap(state -> { // switchMap makes sure that if the state will change the rxBleClient.scanBleDevices() will unsubscribe and thus end the scan
switch (state) {
case READY:
// everything should work
return rxBleClient.scanBleDevices();
case BLUETOOTH_NOT_AVAILABLE:
// basically no functionality will work here
case LOCATION_PERMISSION_NOT_GRANTED:
// scanning and connecting will not work
case BLUETOOTH_NOT_ENABLED:
// scanning and connecting will not work
case LOCATION_SERVICES_NOT_ENABLED:
// scanning will not work
default:
return Observable.empty();
}
})
.subscribe(
rxBleScanResult -> {
// Process scan result here.
},
throwable -> {
// Handle an error here.
}
);
// When done, just unsubscribe.
flowSubscription.unsubscribe();For further BLE interactions the connection is required.
String macAddress = "AA:BB:CC:DD:EE:FF";
RxBleDevice device = rxBleClient.getBleDevice(macAddress);
Subscription subscription = device.establishConnection(false) // <-- autoConnect flag
.subscribe(
rxBleConnection -> {
// All GATT operations are done through the rxBleConnection.
},
throwable -> {
// Handle an error here.
}
);
// When done... unsubscribe and forget about connection teardown :)
subscription.unsubscribe();From BluetoothDevice.connectGatt() Javadoc:
autoConnect boolean: Whether to directly connect to the remote device (false) or to automatically connect as soon as the remote device becomes available (true).
Auto connect concept may be misleading at first glance. With the autoconnect flag set to false the connection will end up with an error if a BLE device is not advertising when the RxBleDevice#establishConnection method is called. From platform to platform timeout after which the error is emitted differs, but in general it is rather tens of seconds than single seconds (~30 s).
Setting the auto connect flag to true allows you to wait until the BLE device becomes discoverable. The RxBleConnection instance won't be emitted until the connection is fully set up. From experience it also handles acquiring wake locks, so it's safe to assume that your Android device will be woken up after the connection has been established - but it is not a documented feature and may change in the future system releases.
Be careful not to overuse the autoConnect flag. On the other side it has negative impact on the connection initialization speed. Scanning window and interval is lowered as it is optimized for background use and depending on Bluetooth parameters it may (and usually do) take more time to establish the connection.
device.establishConnection(false)
.flatMap(rxBleConnection -> rxBleConnection.readCharacteristic(characteristicUUID))
.subscribe(
characteristicValue -> {
// Read characteristic value.
},
throwable -> {
// Handle an error here.
}
);device.establishConnection(false)
.flatMap(rxBleConnection -> rxBleConnection.writeCharacteristic(characteristicUUID, bytesToWrite))
.subscribe(
characteristicValue -> {
// Characteristic value confirmed.
},
throwable -> {
// Handle an error here.
}
);device.establishConnection(false)
.flatMap(rxBleConnection -> Observable.combineLatest(
rxBleConnection.readCharacteristic(firstUUID),
rxBleConnection.readCharacteristic(secondUUID),
YourModelCombiningTwoValues::new
))
.subscribe(
model -> {
// Process your model.
},
throwable -> {
// Handle an error here.
}
);device.establishConnection(false)
.flatMap(rxBleConnection -> rxBleConnection.createNewLongWriteBuilder()
.setCharacteristicUuid(uuid) // required or the .setCharacteristic()
// .setCharacteristic() alternative if you have a specific BluetoothGattCharacteristic
.setBytes(byteArray)
// .setMaxBatchSize(maxBatchSize) // optional -> default 20 or current MTU
// .setWriteOperationAckStrategy(ackStrategy) // optional to postpone writing next batch
.build()
)
.subscribe(
byteArray -> {
// Written data.
},
throwable -> {
// Handle an error here.
}
);device.establishConnection(false)
.flatMap(rxBleConnection -> rxBleConnection.readCharacteristic(characteristicUuid)
.doOnNext(bytes -> {
// Process read data.
})
.flatMap(bytes -> rxBleConnection.writeCharacteristic(characteristicUuid, bytesToWrite))
)
.subscribe(
writeBytes -> {
// Written data.
},
throwable -> {
// Handle an error here.
}
);device.establishConnection(false)
.flatMap(rxBleConnection -> rxBleConnection.setupNotification(characteristicUuid))
.doOnNext(notificationObservable -> {
// Notification has been set up
})
.flatMap(notificationObservable -> notificationObservable) // <-- Notification has been set up, now observe value changes.
.subscribe(
bytes -> {
// Given characteristic has been changes, here is the value.
},
throwable -> {
// Handle an error here.
}
);If you want to observe changes in device connection state just subscribe like below. On subscription you will receive the most current state instantly.
device.observeConnectionStateChanges()
.subscribe(
connectionState -> {
// Process your way.
},
throwable -> {
// Handle an error here.
}
);For connection debugging you can use extended logging
RxBleClient.setLogLevel(RxBleLog.DEBUG);By default RxBleLog uses logcat to print the messages. You can provide your own logger implementation to forward it to other logging libraries such as Timber.
RxBleLog.setLogger((level, tag, msg) -> Timber.tag(tag).log(level, msg));Every error you may encounter is provided via onError callback. Each public method has JavaDoc explaining possible errors.
Important — Prior to version 1.3.0 each failure on BluetoothGatt was effectively closing the connection. From 1.3.0 onwards individual errors will not close the connection if they are not directly related to it. This change does allow to retry operations (i.e. after Android will establish a device bond).
From different interfaces, you can obtain different Observables which exhibit different behaviours.
There are three types of Observables that you may encounter.
- Single value, completing — i.e.
RxBleConnection.readCharacteristic(),RxBleConnection.writeCharacteristic(), etc. - Multiple values, not completing - i.e.
RxBleClient.scan(),RxBleDevice.observeConnectionStateChanges()andObservableemitted byRxBleConnection.setupNotification()/RxBleConnection.setupIndication() - Single value, not completing — these usually are meant for auto cleanup upon unsubscribing i.e.
setupNotification()/setupIndication()— when you will unsubscribe the notification / indication will be disabled
RxBleDevice.establishConnection() is an Observable that will emit a single RxBleConnection but will not complete as the connection may be later a subject to an error (i.e. external disconnection). Whenever you are no longer interested in keeping the connection open you should unsubscribe from it which will cause disconnection and cleanup of resources.
The below table contains an overview of used Observable patterns
| Interface | Function | Number of values | Completes | Hot/Cold |
|---|---|---|---|---|
| RxBleClient | scanBleDevices()* | Infinite | false | cold |
| RxBleClient | observeStateChanges() | Infinite** | false** | hot |
| RxBleDevice | observeConnectionStateChanges() | Infinite | false | hot |
| RxBleDevice | establishConnection()* | Single | false | cold |
| RxBleConnection | discoverServices() | Single | true | cold |
| RxBleConnection | setupNotification()* | Single | false | cold |
| RxBleConnection | setupNotification() emitted Observable | Infinite | false | hot |
| RxBleConnection | setupIndication()* | Single | false | cold |
| RxBleConnection | setupIndication() emitted Observable | Infinite | false | hot |
| RxBleConnection | getCharacteristic() | Single | true | cold |
| RxBleConnection | readCharacteristic() | Single | true | cold |
| RxBleConnection | writeCharacteristic() | Single | true | cold |
| RxBleConnection | readDescriptor() | Single | true | cold |
| RxBleConnection | writeDescriptor() | Single | true | cold |
| RxBleConnection | readRssi() | Single | true | cold |
| RxBleConnection | requestMtu() | Single | true | cold |
| RxBleConnection | queue() | User defined | User defined | cold |
| LongWriteOperationBuilder | build() | Single | true | cold |
* this Observable when unsubscribed closes/cleans up internal resources (i.e. finishes scan, closes a connection, disables notifications)
** this Observable does emit only a single value and finishes in exactly one situation — when Bluetooth Adapter is not available on the device. There is no reason to monitor other states as the adapter does not appear during runtime.
We encourage you to check the package com.polidea.rxandroidble.helpers which contains handy reactive wrappers for some typical use-cases.
Bluetooth Specification specifies formats in which int/float/String values may be stored in characteristics. BluetoothGattCharacteristic has functions for retrieving those (.getIntValue()/.getFloatValue()/.getStringValue()).
Since RxAndroidBle reads and notifications emit byte[] you may want to use ValueIntepreter helper to retrieve the same data easily.
If you would like to observe BluetoothAdapter state changes you can use RxBleAdapterStateObservable.
RxAndroidBle already provides all the necessary bluetooth permissions for you. Recently, Google has started checking these when releasing to the Play Store. If you have ACCESS_COARSE_LOCATION set manually you may run into an issue where your permission do not merge with RxAndroidBle's, resulting in a failure to upload to the Play Store This permission is only required on SDK 23+. If you need this permission on a lower version of Android use:
<uses-permission
android:name="android.permission.ACCESS_COARSE_LOCATION"
android:maxSdkVersion="22"/>Complete usage examples are located in /sample GitHub repo.
compile "com.polidea.rxandroidble:rxandroidble:1.4.3"<dependency>
<groupId>com.polidea.rxandroidble</groupId>
<artifactId>rxandroidble</artifactId>
<version>1.4.3</version>
<type>aar</type>
</dependency>If your are interested in cutting-edge build you can get a SNAPSHOT version of the library.
NOTE: It is built from the top of the master branch and a subject to more frequent changes that may break the API and/or change behavior.
To be able to download it you need to add Sonatype Snapshot repository site to your build.gradle file:
maven { url "https://oss.sonatype.org/content/repositories/snapshots" }Using RxAndroidBle enables you to test your application easily.
Most of the objects that the library uses are implementations of interfaces which can be mocked.
Alternatively one could use MockRxAndroidBle (more info below). Note: Using MockRxAndroidBle in unit tests needs Robolectric.
Sometimes there is a need to develop the application without the access to a physical device. We have created MockRxAndroidBle as a drop-in addon for mocking a simple peripheral.
Unfortunately it is not under active development—PRs are welcomed though. ;)
If you would like to contribute code you can do so through GitHub by forking the repository and sending a pull request.
When submitting code, please make every effort to follow existing conventions and style in order to keep the code as readable as possible. Please also make sure your code compiles by running ./gradlew clean checkstyle test.
- non-commercial — head to StackOverflow #rxandroidble
- commercial — drop an email to [email protected] for more info
Want to talk about it? Join our discussion on Gitter
- Dariusz Seweryn ([email protected])
- Paweł Urban ([email protected])
Contributors, thank you!
Copyright 2016 Polidea Sp. z o.o
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
