# 应用数据与文件

Android 使用与其他平台上基于磁盘的文件系统类似的文件系统。系统为保存应用数据提供了几种选项：

* **应用专用存储** - 用于保存其他应用不应访问的敏感信息的内部存储。
* **共享存储** - 用于应用与其他应用共享的文件，包括媒体、文档和其他文件。
* **首选项** - 用于在键值对中存储私有、原始数据的存储。
* **数据库** - 使用 Room 持久性库在私有数据库中存储结构化数据。

|                                                                                       | 内容类型                 | 访问方法                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       | 所需权限                                                                                                                                                                                                                                                                    |
| ------------------------------------------------------------------------------------- | -------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [应用专用文件](https://developer.android.com/training/data-storage/app-specific)            | 应用专用文件               | <p>从内部存储，使用 <a href="https://developer.android.com/reference/android/content/Context#getFilesDir%28%29">getFilesDir()</a> 和 <a href="https://developer.android.com/reference/android/content/Context#getCacheDir%28%29">getCacheDir()</a></p><p>从外部存储，使用 <a href="https://developer.android.com/reference/android/content/Context#getExternalFilesDir%28java.lang.String%29">getExternalFilesDir()</a> 和 <a href="https://developer.android.com/reference/android/content/Context#getExternalCacheDir%28%29">getExternalCacheDir()</a></p> | <p>内部存储永远不需要权限</p><p>当应用在运行 Android 4.4（API 级别 19）或更高版本的设备上使用时，外部存储不需要权限</p>                                                                                                                                                                                            |
| [媒体](https://developer.android.com/training/data-storage/shared/media)                | 可共享的媒体文件（图像、音频文件、视频） | [MediaStore](https://developer.android.com/reference/android/provider/MediaStore) API                                                                                                                                                                                                                                                                                                                                                                                                                                                      | <p>在 Android 11（API 级别 30）或更高版本上访问其他应用的文件时需要 <strong>READ\_EXTERNAL\_STORAGE</strong></p><p>在 Android 10（API 级别 29）上访问其他应用的文件时需要 <strong>READ\_EXTERNAL\_STORAGE</strong> 或 <strong>WRITE\_EXTERNAL\_STORAGE</strong></p><p>在 Android 9（API 级别 28）或更低版本上访问所有文件都需要权限</p> |
| [文档和其他文件](https://developer.android.com/training/data-storage/shared/documents-files) | 其他类型的可共享内容，包括下载的文件   | 存储访问框架 (Storage Access Framework)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 无                                                                                                                                                                                                                                                                       |
| [应用首选项](https://developer.android.com/training/data-storage/shared-preferences)       | 键值对                  | [Jetpack Preferences](https://developer.android.com/guide/topics/ui/settings/use-saved-values) 库                                                                                                                                                                                                                                                                                                                                                                                                                                           | 无                                                                                                                                                                                                                                                                       |
| 数据库                                                                                   | 结构化数据                | [Room](https://developer.android.com/training/data-storage/room) 持久性库                                                                                                                                                                                                                                                                                                                                                                                                                                                                      | 无                                                                                                                                                                                                                                                                       |

## 参考资料

* [Android 开发者：数据和文件存储概览](https://developer.android.com/training/data-storage)


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