You are previewing Learning Android.

Learning Android

Cover of Learning Android by Marko Gargenta Published by O'Reilly Media, Inc.
  1. Learning Android
    1. SPECIAL OFFER: Upgrade this ebook with O’Reilly
    2. A Note Regarding Supplemental Files
    3. Preface
      1. What’s Inside
      2. Conventions Used in This Book
      3. Using Code Examples
      4. Safari® Books Online
      5. How to Contact Us
      6. Acknowledgments
    4. 1. Android Overview
      1. Android Overview
      2. History
      3. Android Versions
      4. Summary
    5. 2. The Stack
      1. Stack Overview
      2. Linux
      3. Native Libraries
      4. Dalvik
      5. Application Framework
      6. Applications
      7. Summary
    6. 3. Quick Start
      1. Installing the Android SDK
      2. Hello, World
      3. The Emulator
      4. Summary
    7. 4. Main Building Blocks
      1. What Are Main Building Blocks?
      2. A Real-World Example
      3. Activities
      4. Intents
      5. Services
      6. Content Providers
      7. Broadcast Receivers
      8. Application Context
      9. Summary
    8. 5. Yamba Project Overview
      1. The Yamba Application
      2. Design Philosophy
      3. Project Design
      4. Part 1: Android User Interface
      5. Part 2: Preferences, Filesystem, Options Menu, and Intents
      6. Part 3: Android Services
      7. Part 4: Working with Databases
      8. Part 5: Lists and Adapters
      9. Part 6: Broadcast Receivers
      10. Part 7: Content Providers
      11. Part 8: System Services
      12. Summary
    9. 6. Android User Interface
      1. Two Ways to Create a User Interface
      2. Views and Layouts
      3. Starting the Yamba Project
      4. The StatusActivity Layout
      5. The StatusActivity Java Class
      6. Logging in Android
      7. Threading in Android
      8. Other UI Events
      9. Adding Color and Graphics
      10. Alternative Resources
      11. Optimizing the User Interface
      12. Summary
    10. 7. Preferences, the Filesystem, the Options Menu, and Intents
      1. Preferences
      2. The Options Menu
      3. Shared Preferences
      4. The Filesystem Explained
      5. Summary
    11. 8. Services
      1. The Yamba Application Object
      2. UpdaterService
      3. Looping in the Service
      4. Pulling Data from Twitter
      5. Summary
    12. 9. The Database
      1. About SQLite
      2. DbHelper
      3. First Example
      4. Update UpdaterService
      5. Refactoring Status Data
      6. Summary
    13. 10. Lists and Adapters
      1. TimelineActivity
      2. Basic TimelineActivity Layout
      3. About Adapters
      4. TimelineAdapter
      5. ViewBinder: A Better Alternative to TimelineAdapter
      6. Updating the Manifest File
      7. Base Activity
      8. Summary
    14. 11. Broadcast Receivers
      1. About Broadcast Receivers
      2. BootReceiver
      3. The TimelineReceiver
      4. Broadcasting Intents
      5. The Network Receiver
      6. Adding Custom Permissions to Send and Receive Broadcasts
      7. Summary
    15. 12. Content Providers
      1. Creating a Content Provider
      2. Using Content Providers Through Widgets
      3. Summary
    16. 13. System Services
      1. Compass Demo
      2. Location Service
      3. Updating Yamba to Use the Location Service
      4. Intent Service
      5. Sending Notifications
      6. Summary
    17. 14. The Android Interface Definition Language
      1. Implementing the Remote Service
      2. Implementing the Remote Client
      3. Summary
    18. 15. The Native Development Kit (NDK)
      1. What Is and Isn’t the NDK For?
      2. Problems Solved by the NDK
      3. An NDK Example: Fibonacci
      4. Summary
    19. Index
    20. About the Author
    21. Colophon
    22. SPECIAL OFFER: Upgrade this ebook with O’Reilly

Chapter 14. The Android Interface Definition Language

Each application in Android runs in its own process. For security reasons, an application cannot directly access the data of another application. However, a couple of mechanisms allow communication between applications. One such mechanism that you’ve seen throughout this book is Intents. Intents are asynchronous, meaning that you can post a message for someone to receive at some future point in time and just continue with your application.

Every once in a while we need a more direct, synchronous access to another process. There are many ways to implement this across process boundaries, and collectively they are called Interprocess Communication, or IPC for short.

To allow cross-application communication, Android provides its own version of an IPC protocol. One of the biggest challenges in IPC is passing data around, such as when passing parameters to method calls on the remote systems. IPC protocols tend to get complicated because they have to convert data from its in-memory format to a format that’s convenient for sending to another process. This is called marshaling, and the unpacking at the receiver is called unmarshaling.

To help with this, Android provides the Android Interface Definition Language, or AIDL. This lightweight implementation of IPC uses a syntax that is very familiar to Java developers, and there is a tool that automatically creates the hidden code required to connect a client and a remote service.

To illustrate ...

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