Jun 22

Android Things client library for Google Cloud IoT Core


Posted by Wayne Piekarski, Developer Advocate for IoT +WaynePiekarski @WaynePiekarski

We’re releasing a client library to make it easy to use Google Cloud IoT Core from Android Things devices. With just a few lines of code, you can easily connect to the IoT Core MQTT bridge, authenticate the device, publish device telemetry and state, subscribe to configuration changes, and handle errors and network outages.

What is Cloud IoT Core?

Cloud IoT Core is a fully managed service on Google Cloud Platform that allows you to easily and securely connect, manage, and ingest data from millions of globally dispersed devices. Cloud IoT Core, in combination with other services which make up Google’s Cloud IoT platform, provides a complete solution for collecting, processing, analyzing, and visualizing IoT data in real time, to support improved operational efficiency, compliance, or revenue management. Android Things is designed to support everything from collecting telemetry data to powerful computer vision, audio processing, and machine learning applications, all on device, and using Cloud IoT Core, push your data into Google Cloud Platform for further analysis.

Cloud IoT Core client library

The Cloud IoT Core client library was designed to enable Android Things developers to get started with just a few lines of code. The client library handles the networking, threading, and message handling, implementing best practices for authentication, security, error handling, and offline operation.

Cloud IoT Core maintains a device registry that keeps track of approved devices, and each device uses a public key to authenticate with the server. Android Things provides many features to support secure IoT applications, including a hardware-backed Android Keystore that ensures cryptographic key material is protected. The client library supports both RSA and ECC keys, and implements the generation of JSON Web Tokens (JWTs) for authentication with Cloud IoT Core.

Once the connection is established, devices can publish their telemetry data to one or more buckets in the telemetry topic, as well as report their internal state to a separate device state topic. The device state is intended to store information such as software versions or the number of working sensors. The telemetry messages are for all other data from the device, such as actual sensor measurements. Devices can also subscribe to configuration changes published from Cloud IoT Core.

Because IoT devices operate in the real world with poor wireless conditions, the client library provides extensive support for handling errors, and for caching and retransmitting events later. For developers requiring custom offline behavior, the library’s queue is configurable and even replaceable. This provides detailed control over which events to save and the order in which they are sent when back online.

Device provisioning and authentication with Android Things

The Cloud IoT Core client library is part of our overall vision for device provisioning and authentication with Android Things. To learn more about this, watch the video of our presentation from Google I/O 2018:

Sample code

Getting started with the Cloud IoT Core client library is simple. You can simply add the following to the build.gradle file in your Android Things project:

implementation 'com.google.android.things:cloud-iot-core:1.0.0'

The library is also available as open source on GitHub if you prefer to build it yourself. We also have a sample that shows how to implement a sensor hub on Android Things, collecting sensor data from connected sensors and publishing them to a Google Cloud IoT Pub/Sub topic.

It is easy to start using the client library in your own code. The following Kotlin example demonstrates how to create a new configuration and client based on your project.

var configuration = IotCoreConfiguration.Builder().
                         .setProjectId("my-gcp-project")
                         .setRegistry("my-device-registry", "us-central1")
                         .setDeviceId("my-device-id")
                         .setKeyPair(keyPairObject)
                         .build()

var iotCoreClient = IotCoreClient.Builder()
              .setIotCoreConfiguration(configuration)
              .setOnConfigurationListener(onConfigurationListener)
              .setConnectionCallback(connectionCallback)
              .build()

iotCoreClient.connect()

Next, you can publish telemetry information or device state, using the following Kotlin examples.

private fun publishTelemetry(temperature: Float, humidity: Float) {
    // payload is an arbitrary, application-specific array of bytes
    val examplePayload = """{
        |"temperature" : $  temperature,
        |"humidity": $  humidity
        |}""".trimMargin().toByteArray()
    val event = TelemetryEvent(examplePayload, topicSubpath, TelemetryEvent.QOS_AT_LEAST_ONCE)
    iotCoreClient.publishTelemetry(event)
}

private fun publishDeviceState(telemetryFrequency: Int, enabledSensors: Array<String>) {
    // payload is an arbitrary, application-specific array of bytes
    val examplePayload = """{
        |"telemetryFrequency": $  telemetryFrequency,
        |"enabledSensors": $  {enabledSensors.contentToString()}
        |}""".trimMargin().toByteArray()
    iotCoreClient.publishDeviceState(examplePayload)
}

Additional resources

You can learn more about building for Android Things at the developer site. For more information about getting started with Cloud IoT Core, visit the information page and documentation. Finally, join Google’s IoT Developers Community on Google+ to let us know what you’re building with Android Things and Cloud IoT Core!


Android Developers Blog

Jul 15

New Client API Model in Google Play Services

gps

By Magnus Hyttsten, Google Developer Relations

Google Play services 4.2 has now been rolled out to the world, and it’s packed with much-anticipated features such as the brand new Cast API and the updated Drive API.

In addition to these blockbuster announcements, we are also launching a slightly less visible but equally important new API — a new way to connect client APIs and manage API requests. As with the initial Drive API, these changes were available as a developer preview in earlier releases of Google Play services. We’re now happy to graduate those APIs to fully supported and official.

In this post we’ll take a look at the new Google Play services client APIs and what they mean for your apps — for details be sure to read Accessing Google Play services and the API reference documentation.

Connecting Client APIs

The client connection model has now been unified for all the APIs. As you may recall, you were previously required to use separate client classes for each API you wanted to use, for example: PlusClient, GamesClient, etc. Instead, you should now use GoogleApiClient, which allows you to connect to multiple APIs using a single call. This has great advantages such as:

  • Simplicity—The onConnected() method will be called once, and only when connectivity to all the client APIs you are using have been established. This means you do not have to intercept multiple callbacks, one for each API connected, which simplifies the code and state management.
  • Improved user experience—With this design, Google Play services knows about everything your app needs up front. All APIs, all scopes, the works. This means that we can take care of the user consents at once, creating a single consolidated user experience for all the APIs. No more sign-in mid-process terminations, partial state management, etc.

Below is an example of establishing a connection the Google+ and Drive APIs. To see the reference information for this new client connection model, you should check out the com.google.android.gms.common.api package.

@Override
protected void onCreate(Bundle b) {
    super.onCreate(b);

    // Builds single client object that connects to Drive and Google+
    mClient = new GoogleApiClient.Builder(this)
            .addApi(Drive.API)
            .addScope(Drive.SCOPE_FILE)
            .addApi(Plus.API, plusOptions)
            .addScope(Plus.SCOPE_PLUS_LOGIN)
            .addConnectionCallbacks(this)
            .addOnConnectionFailedListener(this)
            .build();
}

@Override
protected void onStart() {
    super.onStart();

    // Connect to Drive and Google+
    mClient.connect();
}

@Override
protected void onConnected(Bundle connectionHint) {
    // All clients are connected
    startRockAndRoll();
}

@Override
protected void onConnectionFailed(ConnectionResult result) {
    // At least one of the API client connect attempts failed
    // No client is connected
    ...
}

Enqueuing API Calls

Another new feature is enqueuing of API calls, which allows you to call read methods before the API clients are connected. This means you can issue these calls up front, for example in onStart/onResume, rather than having to wait and issue them in different callback methods. This is something which will greatly simplify code if your app requires data to be read when it is started. Here is an example of where a call like this can be placed:

@Override
protected void onStart() {
    super.onStart();
    mClient.connect();
}

@Override
protected void onResume() {
    super.onResume();

    // Enqueue operation.
    // This operation will be enqueued and issued once the API clients are connected.
    // Only API retrieval operations are allowed.
    // Asynchronous callback required to not lock the UI thread.
    Plus.PeopleApi.load(mClient, “me”, “you”, “that”).setResultCallback(this);
}

Supporting both Asynchronous and Synchronous Execution

With this release of Google Play services, you now have the option to specify if an API call should execute asynchronously (you will receive a callback once it is finished), or synchronously (the thread will block until the operation has completed). This is achieved by using the classes PendingResult, Result, and Status in the com.google.android.gms.common.api package.

In practice, this means that API operations will return an instance of PendingResult, and you can choose if you want the method to execute asynchronously using setResultCallback or synchronously using await. The following example demonstrates how to synchronously retrieve the metadata for a file and then clear any starred flag setting:

// Must be run in a background task and not on UI thread
new AsyncTask <DriveFile, Void, Void> {
    protected void doInBackground(DriveFile driveFile) {

        // Get the metadata synchronously
        MetaDataResult mdGetResult = driveFile.getMetadata(mClient).await();
        if (!mdGetResult.isSuccess()) {
            // Handle error
        }

        MetaData md = mdGetResult.getMetadata()
        // Perform operations based on metadata

        // Update the meta data, unconditionally clear the starred flag
        MetaDataChangeSet mdCS = new MetadataChangeSet.Builder()
            .setStarred(false)
            .build();

        MetaDataResult mdUpdateResult =driveFile.updateMetaData(mClient,mdCS).await();
        if (!mdUpdateResult.isSuccess()) {
            // Handle error
        }

        … // continue doing other things synchronously
}).execute(fileName);

It should be stressed though that the old best practice rule — do block the UI thread — is still in effect. This means that the execution of this sequence of API calls described above must be performed from a background thread, potentially by using AsyncTask as in the example above.

Moving your apps to the new client API

We believe these changes will make it easier for you to build with Google Play services in your apps. For those of you using the older clients, we recommend refactoring your code as soon as possible to take advantage of these features. Apps deployed using the old client APIs will continue to work since these changes do not break binary compatibility, but the old APIs are now deprecated and we’ll be removing them over time.

That’s it for this time. Google Play services allows Google to provide you with new APIs and features faster than ever, and with the capabilities described in this post, you now have a generic way of using multiple client APIs and executing API calls. Make sure to check out the video below for a closer look at the new client APIs.

To learn more about Google Play services and the APIs available to you through it, visit the Google Services area of the Android Developers site. Details on the APIs are available in the API reference.

For information about getting started with Google Play services APIs, see Set Up Google Play Services SDK

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