ReactiveSensors
Android library monitoring hardware sensors with RxJava.
| Current Branch | Branch | Artifact Id | Build Status | Maven Central |
|---|---|---|---|---|
RxJava1.x | reactivesensors | |||
RxJava2.x | reactivesensors-rx2 |
This is RxJava2.x branch. To see documentation for RxJava1.x, switch to RxJava1.x branch.
min sdk version = 9
JavaDoc is available at: http://pwittchen.github.io/ReactiveSensors/RxJava2.x
Contents
Usage
Code sample below demonstrates how to observe Gyroscope sensor.
Please note that we are filtering events occurring when sensor readings change with ReactiveSensorFilter.filterSensorChanged() method. There's also event describing change of sensor's accuracy, which can be filtered with ReactiveSensorFilter.filterAccuracyChanged() method. When we don't apply any filter, we will be notified both about sensor readings and accuracy changes.
new ReactiveSensors(context).observeSensor(Sensor.TYPE_GYROSCOPE)
.subscribeOn(Schedulers.computation())
.filter(ReactiveSensorFilter.filterSensorChanged())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Consumer<ReactiveSensorEvent>() {
@Override public void call(ReactiveSensorEvent reactiveSensorEvent) {
SensorEvent event = reactiveSensorEvent.getSensorEvent();
float x = event.values[0];
float y = event.values[1];
float z = event.values[2];
String message = String.format("x = %f, y = %f, z = %f", x, y, z);
Log.d("gyroscope readings", message);
}
}
);
}
We can observe any hardware sensor in the same way. You can check list of all sensors in official Android documentation. To get list of all sensors available on the current device, you can use getSensors() method available in ReactiveSensors class.
Setting sampling period
Default sampling period for flowable below is set to SensorManager.SENSOR_DELAY_NORMAL.
Flowable<ReactiveSensorEvent> observeSensor(int sensorType)We can configure sampling period according to our needs with the following flowable:
Flowable<ReactiveSensorEvent> observeSensor(int sensorType,
final int samplingPeriodInUs)We can use predefined values available in SensorManager class from Android SDK:
int SENSOR_DELAY_FASTEST- get sensor data as fast as possibleint SENSOR_DELAY_GAME- rate suitable for gamesint SENSOR_DELAY_NORMAL- rate (default) suitable for screen orientation changesint SENSOR_DELAY_UI- rate suitable for the user interface
We can also define our own integer value in microseconds, but it's recommended to use predefined values.
We can customize RxJava 2 Backpressure Strategy for our flowable with method:
Flowable<ReactiveSensorEvent> observeSensor(int sensorType, final int samplingPeriodInUs,
final Handler handler, final BackpressureStrategy strategy)Default Backpressure Strategy is BUFFER.
Example
Exemplary application, which gets readings of various sensors is located in app directory of this repository. You can easily change SENSOR_TYPE variable to read values from a different sensor in a given samples.
Good practices
Checking whether sensor exists
We should check whether device has concrete sensor before we start observing it.
We can do it in the following way:
if (reactiveSensors.hasSensor(SENSOR_TYPE)) {
// observe sensor
}
else {
// show error message
}
Letting it crash
We can let our subscription crash and handle situation when device does not have given sensor e.g. in the Consumer<Throwable>() implementation (if we want to return Disposable) or in the onError(throwable) method implementation of the Subscriber. Other types of errors can be handled there as well.
new ReactiveSensors(context).observeSensor(Sensor.TYPE_GYROSCOPE)
.subscribeOn(Schedulers.computation())
.filter(ReactiveSensorFilter.filterSensorChanged())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Consumer<ReactiveSensorEvent>() {
@Override public void accept(ReactiveSensorEvent reactiveSensorEvent) throws Exception {
// handle reactiveSensorEvent
}
}
, new Consumer<Throwable>() {
@Override public void accept(Throwable throwable) throws Exception {
if (throwable instanceof SensorNotFoundException) {
textViewForMessage.setText("Sorry, your device doesn't have required sensor.");
}
}
}
);
Subscribing and disposing flowables
When we are using Disposables in Activity, we should subscribe them in onResume() method and dispose them in onPause() method.
Filtering stream
When we want to receive only sensor updates, we should use ReactiveSensorFilter.filterSensorChanged() method in filter(...) method from RxJava.
When we want to receive only accuracy updates, we should use ReactiveSensorFilter.filterAccuracyChanged() method in filter(...) method from RxJava.
If we don't apply any filter, we will receive both accuracy and sensor readings updates.
Other practices
See also Best Practices for Accessing and Using Sensors.
Download
You can depend on the library through Maven:
<dependency>
<groupId>com.github.pwittchen</groupId>
<artifactId>reactivesensors-rx2</artifactId>
<version>0.2.0</version> </dependency>or through Gradle:
dependencies {
compile 'com.github.pwittchen:reactivesensors-rx2:0.2.0'
}
Tests
Tests are available in library/src/androidTest/java/ directory and can be executed on emulator or Android device from Android Studio or CLI with the following command:
./gradlew connectedCheck Code style
Code style used in the project is called SquareAndroid from Java Code Styles repository by Square available at: https://github.com/square/java-code-styles. Currently, library doesn't have checkstyle verification attached. It can be done in the future.
Static code analysis
Static code analysis runs Checkstyle, FindBugs, PMD and Lint. It can be executed with command:
./gradlew check Reports from analysis are generated in library/build/reports/ directory.
References
License
Copyright 2015 Piotr Wittchen 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.