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Asynchronous Android Programming

Asynchronous Android Programming

By : Vasconcelos, Liles
5 (3)
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Asynchronous Android Programming

Asynchronous Android Programming

5 (3)
By: Vasconcelos, Liles

Overview of this book

Asynchronous programming has acquired immense importance in Android programming, especially when we want to make use of the number of independent processing units (cores) available on the most recent Android devices. With this guide in your hands you’ll be able to bring the power of Asynchronous programming to your own projects, and make your Android apps more powerful than ever before! To start with, we will discuss the details of the Android Process model and the Java Low Level Concurrent Framework, delivered by Android SDK. We will also guide you through the high-level Android-specific constructs available on the SDK: Handler, AsyncTask, and Loader. Next, we will discuss the creation of IntentServices, Bound Services and External Services, which can run in the background even when the user is not interacting with it. You will also discover AlarmManager and JobScheduler APIs, which are used to schedule and defer work without sacrificing the battery life. In a more advanced phase, you will create background tasks that are able to execute CPU-intensive tasks in a native code-making use of the Android NDK. You will be then guided through the process of interacting with remote services asynchronously using the HTTP protocol or Google GCM Platform. Using the EventBus library, we will also show how to use the Publish-Subscribe software pattern to simplify communication between the different Android application components by decoupling the event producer from event consumer. Finally, we will introduce RxJava, a popular asynchronous Java framework used to compose work in a concise and reactive way. Asynchronous Android will help you to build well-behaved applications with smooth responsive user interfaces that delight the users with speedy results and data that’s always fresh.
Table of Contents (14 chapters)
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2
2. Performing Work with Looper, Handler, and HandlerThread
13
Index

Combining Observables

In the previous example, we used two Observable to create a simple sequence of network operations. The second asynchronous operation operated with the result of the first operation and the two operations that executed serially produced a String result that updates the UI.

In our next example, we will run two tasks in parallel and combine the results of both operations using a combining RxJava operator. Each operation will retrieve asynchronously a JSON Object from the network and combine both results in the JSON Object to produce the JSON String passed to the UI main Thread.

Since we only want to emit one Event or an error from the operation, we are going to use, for the first time, a special kind of Observer, Single.

While an Observable is able to invoke onNext, onError, and onCompleted Observer functions, a Single entity will only invoke either onSuccess or onError to a SingleSubscriber:

 // Success callback invoked on success
 void onSuccess(T value);

 // Callback...

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