Android Studio

Usage

Make sure you have followed android build instructions already.

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

Use the flag --sdk AndroidStudioDefault to create and use a custom sdk directory and avoid issues with gclient sync and to use emulators. This will become the default soon.

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

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

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

For first-time Android Studio users:

• Only run the setup wizard if you are planning to use emulators.
  • The wizard will force you to download SDK components that are only needed for emulation.
  • To skip it, select “Cancel” when it comes up.

To import the project:

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

If you‘re asked to use Studio’s Android SDK:

• No. (Always use your project's SDK configured by generate_gradle.py)

If you‘re asked to use Studio’s Gradle wrapper:

• Yes.

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

Pass --canary or --beta to avoid the “A newer version of gradle is available” notification.

• 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 when used with --all by default.

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. It is very slow to build all these generated files and they rarely change. The generator script does not do anything with them by default. If --full is passed then the generator script builds and extracts them all to extracted-srcjars/ subdirectories for each target that contains them. This is the reason that the _all pseudo module may contain multiple copies of generated files.

** TLDR:** Re-generate project files with --full when generated files change ( includes R.java) and to remove some red underlines in java files.

Native Files

A new experimental option is now available to enable editing native C/C++ files with Android Studio. Pass in any number of --native-target [target name] flags in order to try it out. The target must be the full path and name of a valid gn target (no shorthands). This will require you to install cmake and ndk when prompted. Accept Android Studio's prompts for these SDK packages.

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 these changes will be overwritten on your next invocation of generate_gradle.py.

Example:

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

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

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 (as of May 10, 2018)

What works

• Android Studio v3.0-v3.2.
• Java editing.
• Native code editing (experimental).
• Instrumentation tests included as androidTest.
• 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 (yet) (crbug)

• Gradle being aware of assets.
• Having the “Make Project” button work correctly.