Android Studio

Usage

build/android/gradle/generate_gradle.py --output-directory out-gn/Debug

This creates a project at out-gn/Debug/gradle. To create elsewhere:

build/android/gradle/generate_gradle.py --output-directory out-gn/Debug --project-dir my-project

By default, only common targets are generated. To customize the list of targets to generate projects for:

build/android/gradle/generate_gradle.py --output-directory out-gn/Debug --target //some:target_apk --target //some/other:target_apk

For first-time Android Studio users:

  • Avoid running the setup wizard.
    • The wizard will force you to download unwanted SDK components to //third_party/android_tools.
    • To skip it, select “Cancel” when it comes up.

To import the project:

  • Use “Import Project”, and select the directory containing the generated project.

You need to re-run generate_gradle.py whenever BUILD.gn files change.

  • After regenerating, Android Studio should prompt you to “Sync”. If it doesn't, use:
    • Help -> Find Action -> Sync Project with Gradle Files

How it Works

Android Studio integration works by generating build.gradle files based on GN targets. Each android_apk and android_library target produces a separate Gradle sub-project.

Symlinks and .srcjars

Gradle supports source directories but not source files. However, some java/src/ directories in Chromium are split amonst multiple GN targets. To accomodate this, the script detects such targets and creates a symlinked-java/ directory to point gradle at. Be warned that creating new files from Android Studio within these symlink-based projects will cause new files to be created in the generated symlinked-java/ rather than the source tree where you want it.

** TLDR:** Always create new files outside of Android Studio.

Most generated .java files in GN are stored as .srcjars. Android Studio does not have support for them, and so the generator script builds and extracts them all to extracted-srcjars/ subdirectories for each target that contains them.

** TLDR:** Always re-generate project files when .srcjars change (this includes R.java).

Android Studio Tips

  • Configuration instructions can be found here. One suggestions:
    • Launch it with more RAM: STUDIO_VM_OPTIONS=-Xmx2048m /opt/android-studio-stable/bin/studio-launcher.sh
  • If you ever need to reset it: rm -r ~/.AndroidStudio*/
  • Import Android style settings:
    • Help -> Find Action -> Code Style -> Java -> Manage -> Import
      • Select third_party/android_platform/development/ide/intellij/codestyles/AndroidStyle.xml

Useful Shortcuts

  • Shift - Shift: Search to open file or perform IDE action
  • Ctrl + N: Jump to class
  • Ctrl + Shift + T: Jump to test
  • Ctrl + Shift + N: Jump to file
  • Ctrl + F12: Jump to method
  • Ctrl + G: Jump to line
  • Shift + F6: Rename variable
  • Ctrl + Alt + O: Organize imports
  • Alt + Enter: Quick Fix (use on underlined errors)

Building from the Command Line

Gradle builds can be done from the command-line after importing the project into Android Studio (importing into the IDE causes the Gradle wrapper to be added). This wrapper can also be used to invoke gradle commands.

cd $GRADLE_PROJECT_DIR && bash gradlew

The resulting artifacts are not terribly useful. They are missing assets, resources, native libraries, etc.

  • Use a gradle daemon to speed up builds:
    • Add the line org.gradle.daemon=true to ~/.gradle/gradle.properties, creating it if necessary.

Status (as of Sept 21, 2016)

What works

  • Tested with Android Studio v2.2.
  • Basic Java editing and compiling works.

What doesn't work (yet) (crbug)

  • JUnit Test targets
  • Better support for instrumentation tests (they are treated as non-test .apks right now)
  • Make gradle aware of resources and assets
  • Make gradle aware of native code via pointing it at the location of our .so
  • Add a mode in which gradle is responsible for generating R.java
  • Add support for native code editing
  • Make the “Make Project” button work correctly