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 12. Content Providers

Content providers are Android building blocks that can expose data across the boundaries between application sandboxes. As you recall, each application in Android runs in its own process with its own permissions. This means that an application cannot see another app’s data. But sometimes you want to share data across applications. This is where content providers become very useful.

Take your contacts, for example. You might have a large database of contacts on your device, which you can view via the Contacts app as well as via the Dialer app. Some devices, such as HTC Android models, might even have multiple versions of the Contacts and Dialer apps. It would not make a lot of sense to have similar data live in multiple databases.

Content providers let you centralize content in one place and have many different applications access it as needed. In the case of the contacts on your phone, there is actually a ContactProvider application that contains a content provider, and other applications access the data via this interface. The interface itself is fairly simple: it has the same insert(), update(), delete(), and query() methods we saw in Chapter 9.

Android uses content providers quite a bit internally. In addition to contacts, your settings represent another example, as do all your bookmarks. All the media in the system is also registered with MediaStore, a content provider that dispenses images, music, and videos in your device.

Creating a Content Provider ...

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