# Checking out and building Chromium for Android There are instructions for other platforms linked from the [get the code](get_the_code.md) page. ## Instructions for Google Employees Are you a Google employee? See [go/building-android-chrome](https://goto.google.com/building-android-chrome) instead. [TOC] ## System requirements * A 64-bit Intel machine running Linux with at least 8GB of RAM. More than 16GB is highly recommended. * At least 100GB of free disk space. * You must have Git and Python installed already. Most development is done on Ubuntu. Other distros may or may not work; see the [Linux instructions](linux/build_instructions.md) for some suggestions. Building the Android client on Windows or Mac is not supported and doesn't work. ## Install depot\_tools Clone the `depot_tools` repository: ```shell git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git ``` Add `depot_tools` to the end of your PATH (you will probably want to put this in your `~/.bashrc` or `~/.zshrc`). Assuming you cloned `depot_tools` to `/path/to/depot_tools`: ```shell export PATH="$PATH:/path/to/depot_tools" ``` ## Get the code Create a `chromium` directory for the checkout and change to it (you can call this whatever you like and put it wherever you like, as long as the full path has no spaces): ```shell mkdir ~/chromium && cd ~/chromium fetch --nohooks android ``` If you don't want the full repo history, you can save a lot of time by adding the `--no-history` flag to `fetch`. Expect the command to take 30 minutes on even a fast connection, and many hours on slower ones. If you've already installed the build dependencies on the machine (from another checkout, for example), you can omit the `--nohooks` flag and `fetch` will automatically execute `gclient runhooks` at the end. When `fetch` completes, it will have created a hidden `.gclient` file and a directory called `src` in the working directory. The remaining instructions assume you have switched to the `src` directory: ```shell cd src ``` ### Converting an existing Linux checkout If you have an existing Linux checkout, you can add Android support by appending `target_os = ['linux', 'android']` to your `.gclient` file (in the directory above `src`): ```shell echo "target_os = [ 'android' ]" >> ../.gclient ``` Then run `gclient sync` to pull the new Android dependencies: ```shell gclient sync ``` (This is the only difference between `fetch android` and `fetch chromium`.) ### Install additional build dependencies Once you have checked out the code, run ```shell build/install-build-deps-android.sh ``` to get all of the dependencies you need to build on Linux, *plus* all of the Android-specific dependencies (you need some of the regular Linux dependencies because an Android build includes a bunch of the Linux tools and utilities). ### Run the hooks Once you've run `install-build-deps` at least once, you can now run the Chromium-specific hooks, which will download additional binaries and other things you might need: ```shell gclient runhooks ``` *Optional*: You can also [install API keys](https://www.chromium.org/developers/how-tos/api-keys) if you want your build to talk to some Google services, but this is not necessary for most development and testing purposes. ## Setting up the build Chromium uses [Ninja](https://ninja-build.org) as its main build tool along with a tool called [GN](https://gn.googlesource.com/gn/+/main/docs/quick_start.md) to generate `.ninja` files. You can create any number of *build directories* with different configurations. To create a build directory which builds Chrome for Android, run `gn args out/Default` and edit the file to contain the following arguments: ```gn target_os = "android" target_cpu = "arm64" # See "Figuring out target_cpu" below ``` * You only have to run this once for each new build directory, Ninja will update the build files as needed. * You can replace `Default` with another name, but it should be a subdirectory of `out`. * For other build arguments, including release settings, see [GN build configuration](https://www.chromium.org/developers/gn-build-configuration). The default will be a debug component build. * For more info on GN, run `gn help` on the command line or read the [quick start guide](https://gn.googlesource.com/gn/+/main/docs/quick_start.md). Also be aware that some scripts (e.g. `tombstones.py`, `adb_gdb.py`) require you to set `CHROMIUM_OUTPUT_DIR=out/Default`. ### Figuring out target\_cpu The value of [`target_cpu`](https://gn.googlesource.com/gn/+/main/docs/reference.md#var_target_cpu) determines what instruction set to use for native code. Given a device (or emulator), you can determine the correct instruction set with `adb shell getprop ro.product.cpu.abi`: | `getprop ro.product.cpu.abi` output | `target_cpu` value | |-------------------------------------|--------------------| | `arm64-v8a` | `arm64` | | `armeabi-v7a` | `arm` | | `x86` | `x86` | | `x86_64` | `x64` | *** promo `arm` and `x86` may optionally be used instead of `arm64` and `x64` for non-WebView targets. This is also allowed for Monochrome, but only when not set as the WebView provider. *** ## Build Chromium Build Chromium with Ninja using the command: ```shell autoninja -C out/Default chrome_public_apk ``` (`autoninja` is a wrapper that automatically provides optimal values for the arguments passed to `ninja`.) You can get a list of all of the other build targets from GN by running `gn ls out/Default` from the command line. To compile one, pass the GN label to Ninja with no preceding "//" (so, for `//chrome/test:unit_tests` use `autoninja -C out/Default chrome/test:unit_tests`). ### Multiple Chrome Targets The Google Play Store allows apps to send customized `.apk` or `.aab` files depending on the version of Android running on a device. Chrome uses this feature to package optimized versions for different OS versions. 1. `chrome_modern_public_bundle` (ChromeModernPublic.aab) * `minSdkVersion=21` (Lollipop). * Uses [Crazy Linker](https://cs.chromium.org/chromium/src/base/android/linker/BUILD.gn?rcl=6bb29391a86f2be58c626170156cbfaa2cbc5c91&l=9). * Stores native library with "crazy." prefix to prevent extraction. * WebView packaged independently (`system_webview_bundle`). 2. `monochrome_public_bundle` (MonochromePublic.aab) * `minSdkVersion=24` (Nougat). * Contains both Chrome and WebView (to save disk space). * Does not use Crazy Linker (WebView requires system linker). 3. `trichrome_chrome_bundle` (TrichromeChrome.aab) * `minSdkVersion=29` (Android 10). * Native code shared with WebView through a "Static Shared Library APK": `trichrome_library_apk` * Corresponding WebView target: `trichrome_webview_bundle` 4. `chrome_public_apk` (ChromePublic.apk) * Used for only local development and tests (simpler than using bundle targets). * Same configuration as chrome_modern_public_bundle, except without separating things into modules. *** note **Notes:** * These instructions use `chrome_public_apk`, but any of the other targets can be substituted. * For more about bundles, see [android_dynamic feature modules.md](android_dynamic_feature_modules.md). * For more about native library packaging & loading, see [android_native_libraries.md](android_native_libraries.md). * There are closed-source equivalents to these targets (for Googlers), which are identical but link in some extra code. *** ## Updating your checkout To update an existing checkout, you can run ```shell $ git rebase-update $ gclient sync ``` The first command updates the primary Chromium source repository and rebases any of your local branches on top of tip-of-tree (aka the Git branch `origin/main`). If you don't want to use this script, you can also just use `git pull` or other common Git commands to update the repo. The second command syncs dependencies to the appropriate versions and re-runs hooks as needed. ## Installing and Running Chromium on a device ### Plug in your Android device Make sure your Android device is plugged in via USB, and USB Debugging is enabled. To enable USB Debugging: * Navigate to Settings \> About Phone \> Build number * Click 'Build number' 7 times * Now navigate back to Settings \> Developer Options * Enable 'USB Debugging' and follow the prompts You may also be prompted to allow access to your PC once your device is plugged in. You can check if the device is connected by running: ```shell third_party/android_sdk/public/platform-tools/adb devices ``` Which prints a list of connected devices. If not connected, try unplugging and reattaching your device. ### Enable apps from unknown sources Allow Android to run APKs that haven't been signed through the Play Store: * Enable 'Unknown sources' under Settings \> Security In case that setting isn't present, it may be possible to configure it via `adb shell` instead: ```shell third_party/android_sdk/public/platform-tools/adb shell settings put global verifier_verify_adb_installs 0 ``` ### Build the full browser ```shell autoninja -C out/Default chrome_public_apk ``` And deploy it to your Android device: ```shell out/Default/bin/chrome_public_apk install ``` The app will appear on the device as "Chromium". ### Build Content shell Wraps the content module (but not the /chrome embedder). See [https://www.chromium.org/developers/content-module](https://www.chromium.org/developers/content-module) for details on the content module and content shell. ```shell autoninja -C out/Default content_shell_apk out/Default/bin/content_shell_apk install ``` this will build and install an Android apk under `out/Default/apks/ContentShell.apk`. ### Build WebView [Android WebView](https://developer.android.com/reference/android/webkit/WebView.html) is a system framework component. Since Android KitKat, it is implemented using Chromium code (based off the [content module](https://dev.chromium.org/developers/content-module)). If you want to build the complete Android WebView framework component and test the effect of your chromium changes in Android apps using WebView, you should follow the [Android AOSP + chromium WebView instructions](https://www.chromium.org/developers/how-tos/build-instructions-android-webview) ### Running For Content shell: ```shell out/Default/bin/content_shell_apk launch [--args='--foo --bar'] http://example.com ``` For Chrome public: ```shell out/Default/bin/chrome_public_apk launch [--args='--foo --bar'] http://example.com ``` ### Logging and debugging Logging is often the easiest way to understand code flow. In C++ you can print log statements using the LOG macro. In Java, refer to [android_logging.md](android_logging.md). You can see these log via `adb logcat`, or: ```shell out/Default/bin/chrome_public_apk logcat ``` Logcat supports an additional feature of filtering and highlighting user-defined patterns. To use this mechanism, define a shell variable: `CHROMIUM_LOGCAT_HIGHLIGHT` and assign your desired pattern. The pattern will be used to search for any substring (ie. no need to prefix or suffix it with `.*`), eg: ```shell export CHROMIUM_LOGCAT_HIGHLIGHT='(WARNING|cr_Child)' out/Default.bin/chrome_public_apk logcat # Highlights messages/tags containing WARNING and cr_Child strings. ``` Note: both _Message_ and _Tag_ portion of logcat are matched against the pattern. To debug C++ code, use one of the following commands: ```shell out/Default/bin/content_shell_apk gdb out/Default/bin/chrome_public_apk gdb ``` See [Android Debugging Instructions](android_debugging_instructions.md) for more on debugging, including how to debug Java code. ### Testing For information on running tests, see [Android Test Instructions](/testing/android/docs/README.md) ### Faster Edit/Deploy #### GN Args Args that affect build speed: * `is_component_build = true` *(default=`is_debug`)* * What it does: Uses multiple `.so` files instead of just one (faster links) * `is_java_debug = true` *(default=`is_debug`)* * What it does: Disables ProGuard (slow build step) * `treat_warnings_as_errors = false` *(default=`true`)* * Causes any compiler warnings or lint checks to not fail the build. * Allows you to iterate without needing to satisfy static analysis checks. * `android_static_analysis = "build_server"` *(default=`"on"`)* * Offloads static analysis steps to the build server. Explained below. * Set this to `"off"` if you want to turn off static analysis altogether. * `incremental_install = true` *(default=`false`)* * Makes build and install quite a bit faster. Explained in a later section. #### Running static analysis with the build server Normally analysis build steps like lint and errorprone will run in parallel with the rest of the build. The build will then wait for all analysis steps to complete successfully. By offloading analysis build steps to a separate build server to be run lazily at a low priority when the machine is idle, the actual build can complete up to 50-80% faster. There are **two** steps to using the build server. 1. Add the gn arg `android_static_analysis = "build_server"` 2. Run the script at [//build/android/fast_local_dev_server.py][fast_local_dev] All your local builds will now forward analysis steps to this server, including android lint, errorprone, bytecode processor. If you run (2) in a terminal, the output of the checks will be displayed there. Alternatively, you can set up the server as a Linux service, so it runs on the background and starts on boot. If you're using systemd: Save the following as /etc/systemd/user/fast-local-dev-server.service. ``` [Unit] Description=Chrome server for android build static analysis [Service] Type=simple ExecStart= Restart=always [Install] WantedBy=default.target ``` Then ```bash systemctl --user daemon-reload systemctl --user enable fast-local-dev-server systemctl --user start fast-local-dev-server ``` The output can be inspected with ``` journalctl --user -e -u fast-local-dev-server ``` **Note**: Since the build completes before the analysis checks finish, the build will not fail if an analysis check fails. Make sure to check the terminal that the server is running in at regular intervals to fix outstanding issues caught by these analysis checks. [fast_local_dev]: https://source.chromium.org/chromium/chromium/src/+/main:build/android/fast_local_dev_server.py #### Incremental Install [Incremental Install](/build/android/incremental_install/README.md) uses reflection and sideloading to speed up the edit & deploy cycle (normally < 10 seconds). The initial launch of the apk will be a lot slower on older Android versions (pre-N) where the OS needs to pre-optimize the side-loaded files, but then be only marginally slower after the first launch. To enable Incremental Install, add the gn args: ```gn incremental_install = true ``` Some APKs (e.g. WebView) do not work with `incremental install = true` and are always built as normal APKs. This behavior is controlled via `never_incremental = true`. ## Installing and Running Chromium on an Emulator Running on an emulator is the same as on a device. Refer to [android_emulator.md](android_emulator.md) for setting up emulators. ## Tips, tricks, and troubleshooting ### Rebuilding libchrome.so for a particular release These instructions are only necessary for Chrome 51 and earlier. In the case where you want to modify the native code for an existing release of Chrome for Android (v25+) you can do the following steps. Note that in order to get your changes into the official release, you'll need to send your change for a codereview using the regular process for committing code to chromium. 1. Open Chrome on your Android device and visit chrome://version 2. Copy down the id listed next to "Build ID:" 3. Go to [http://storage.googleapis.com/chrome-browser-components/BUILD\_ID\_FROM\_STEP\_2/index.html](http://storage.googleapis.com/chrome-browser-components/BUILD_ID_FROM_STEP_2/index.html) 4. Download the listed files and follow the steps in the README.