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Android Studio

[TOC]

Usage

Make sure you have followed android build instructions already.

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

The above commands create a project dir gradle under your output directory. Use --project-dir <project-dir> to change this.

To import the project:

  • Use "Import Project", and select the directory containing the generated project, e.g. out/Debug/gradle.

See android_test_instructions.md for more information about building and running emulators.

If you're asked to use Studio's Android SDK: No.

If you're asked to use Studio's Gradle wrapper: Yes.

You need to re-run generate_gradle.py whenever BUILD.gn files change, for example, when you add a new directory containing source files.

Since newer gradle versions are released regularly and it is not possible to set a gradle version in root.jinja that is the newest for each version of Android Studio, feel free to update the value in build.gradle locally when you see the "A newer version of gradle is available" notification. This will likely happen each time after generate_gradle.py runs.

  • After regenerating, Android Studio should prompt you to "Sync". If it doesn't, try some of the following options:
    • File -> "Sync Project with Gradle Files"
    • Button with two arrows on the right side of the top strip.
    • Help -> Find Action -> "Sync Project with Gradle Files"
    • After gn clean you may need to restart Android Studio.
    • File -> "Invalidate Caches / Restart..."

How It Works

By default, only an _all module containing all java apk targets is generated. If just one apk target is explicitly specified, then a single apk module is generated.

To see more detailed structure of gn targets, the --split-projects flag can be used. This will generate one module for every gn target in the dependency graph. This can be very slow.

Excluded Files

Gradle supports source directories but not source files. However, files in Chromium are used amongst multiple targets. To accommodate this, the script detects such targets and creates exclude patterns to exclude files not in the current target. The editor does not respect these exclude patterns, so the _all pseudo module is added which includes directories from all targets. This allows imports and refactoring to be across all targets.

Extracting .srcjars

Most generated .java files in GN are stored as .srcjars. Android Studio does not support them. The generator script builds and extracts them to extracted-srcjars/ subdirectories for each target that contains generated files. This is the reason that the _all pseudo module may contain multiple copies of generated files. It can be slow to build all these generated files, so if --fast is passed then the generator script skips building and extracting them.

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

Native Files

This option is no longer supported since Android Studio is very slow when editing in a code base with a large number of C++ files, and Chromium has a lot of C++ code. It is recommended to use VS Code to edit native files and stick to just editing java files in Android Studio.

If you still want to enable editing native C/C++ files with Android Studio, pass in any number of --native-target [target name] flags in order to use it. The target must be the full path and name of a valid gn target (no short-forms). This will require you to install cmake and ndk when prompted. Accept Android Studio's prompts for these SDK packages.

You need to disable a new gradle option in order to edit native files: File -> Settings -> Experimental -> Gradle and uncheck "Only resolve selected variants".

This is not necessary, but to avoid "This file is not part of the project...", you can either add an extra --native-target flag or simply copy and paste the absolute path to that file into the CMakeLists.txt file alongside the existing file paths. Note that changes to CMakeLists.txt will be overwritten on your next invocation of generate_gradle.py.

Example:

build/android/gradle/generate_gradle.py --native-target //chrome/android:libchrome

Tips

  • Use environment variables to avoid having to specify --output-directory.
    • Example: Append export CHROMIUM_OUT_DIR=out; export BUILDTYPE=Debug to your ~/.bashrc to always default to out/Debug.
  • Using the Java debugger is documented here.
  • 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 Chromium-specific style and inspections settings:
    • Help -> Find Action -> "Code Style" (settings) -> Java -> Scheme -> Import Scheme
      • Select tools/android/android_studio/ChromiumStyle.xml -> OK
    • Help -> Find Action -> "Inspections" (settings) -> Profile -> Import profile
      • Select tools/android/android_studio/ChromiumInspections.xml -> OK
  • Turn on automatic import:
    • Help -> Find Action -> "Auto Import"
      • Tick all the boxes under "Java" and change the dropdown to "All".
  • Turn on documentation on mouse hover:
    • Help -> Find Action -> "Show quick documentation on mouse move"
  • Turn on line numbers:
    • Help -> Find Action -> "Show line numbers"
  • Turn off indent notification:
    • Help -> Find Action -> "Show notifications about detected indents"
  • Format changed files (Useful for changes made by running code inspection):
    • Set up version control
      • File -> Settings -> Version Control
      • Add src directories
    • Commit changes and reformat
      • Help -> Find Action -> "Commit Changes"
      • Check "Reformat code" & "Optimize imports" and commit
  • Change theme from GTK+ to another one to avoid invisible menus.
    • Help -> Find Action -> "Theme: Settings > Appearance"

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)
  • F2: Find next error

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 using the gradlew script:
    • Add the line org.gradle.daemon=true to ~/.gradle/gradle.properties, creating it if necessary.

Status

What works

  • Android Studio v2021 & v2022.
  • Java editing.
    • Application code in main sourceset.
    • Instrumentation test code in androidTest sourceset.
  • Native code editing (deprecated, use VS Code instead).
  • Symlinks to existing .so files in jniLibs (doesn't generate them).
  • Editing resource xml files
  • Layout editor (limited functionality).
  • Java debugging (see here).
  • Import resolution and refactoring across java files.
  • Correct lint and AndroidManifest when only one target is specified.
  • Emulators (more docs coming soon).
  • Separate Android SDK for Android Studio.

What doesn't work

  • Gradle being aware of assets.
  • Having the "Make Project" button work correctly.
    • Stick to using autoninja to build targets and just use Android Studio for editing java source files.
  • No active work is underway or planned to expand Android Studio support.