1# //base/android 2 3This directory contains: 4 5* C++ APIs that are broadly useful and are unique to `target_os="android"`, and 6* Java APIs that are broadly useful, along C++ bindings when necessary. 7 8This directory does not contain Android-specific implementations / extensions 9to APIs declared directly in `//base`. Those live in `//base/*_android.cc`, or 10behind `#ifdef`s. 11 12## Adding New APIs 13 14The advice laid out in [//base/README.md] applies to this directory as well. 15The bars for what APIs should exist and for code quality are generally higher 16than for other directories. If you find yourself wanting to add a new API, you 17should expect that code reviews take multiple revisions and that they be met 18with (respectful) scrutiny. 19 20If you are not sure whether an API would make sense to add, you can ask via 21[email protected]. 22It is common to add APIs to `//chrome` (or elsewhere) first, and move them into 23`//base` after their usefulness has been proven. 24 25[//base/README.md]: /base/README.md 26 27### What Uses //base/android? 28 29The main two clients are Chrome and WebView, but it is also used by other 30Chromium-based apps, such as Chromecast and Chrome Remote desktop. Some 31`//base/android` classes are used by `//build` (this is a layering violation, 32tracked in [crbug/1364192] and [crbug/1377351]). 33 34Two considerations for WebView: 35 361. The application Context is that of the host app's. 372. The UI thread might be different from the main thread. 38 39[crbug/1364192]: https://crbug.com/1364192 40[crbug/1377351]: https://crbug.com/1377351 41 42 43### New API Checklist 44 45Here is a list of checks you should go through when adding a new API: 46 471. The functionality does not already exist in system libraries (Java APIs, 48 Android SDK) or in already adopted `third_party` libraries, such as AndroidX. 492. Reasonable effort has been made to ensure the new API is discoverable. E.g.: 50 Coordinate refactorings of existing patterns to it, add a [presubmit check], 51 to recommend it, etc. 523. Tests (ideally Robolectric) are added. 534. Thought has been put into API design. 54 * E.g. adding `@Nullable`, or `@DoNotMock` 55 * E.g. adding test helpers, such as `ForTesting()` methods or `TestRule`s 56 * E.g. adding asserts or comments about thread-safety 57 * E.g. could usage of the API be made harder to get wrong? 58 59[presumbit check]: https://chromium.googlesource.com/chromium/src/+/main/build/android/docs/java_toolchain.md#Static-Analysis-Code-Checks 60 61### Choosing a Reviewer 62 63All members of [`//base/android/OWNERS`] will be CC'ed on reviews through a 64[`//WATCHLIST`] entry. For new APIs, feel free to pick a reviewer at random. 65For modifying existing files, it is best to use a reviewer from prior changes to 66the file. 67 68[`//base/android/OWNERS`]: /base/android/OWNERS 69[`//WATCHLIST`]: /WATCHLIST 70