When new Android versions become available, the following steps should be taken in order to fully support the new API version in the Flutter engine. These steps only change the engine to build against and target the new API and do not guarantee that everything works with the changes in the new Android API.

Update the Buildroot: ​

In build/config/android/config.gni, edit default_android_sdk_version and default_android_sdk_build_tools_version to the new Android version.

NOTE: There is an ongoing effort to move the flutter/buildroot repo into the flutter/engine repo, so this file may have moved by the time you are following these instructions.

Upload new SDK and other dependencies to CIPD: ​

Flutter now includes a script to download, package, and upload the Android SDK to CIPD. These CIPD packages are then used as dependencies by the Flutter engine and recipes (go/flutter-luci-recipes) so that there is a stable archived version of the Android SDK to depend on. The script is located in the Flutter engine repo under tools/android-sdk/create_cipd_packages.sh.

To upload packages to CIPD (either with the script or manually), the flutter-cipd-writers role is required in order to complete this operation. Googlers can apply for access here. Once this role is granted, cipd auth-login must be run in order for cipd to update the user's available roles.

Edit tools/android-sdk/packages.txt to refer to the updated versions you want. The format for each line in packages.txt is <package_name>:<subdirectory_to_upload>. Typically, each <package_name> should be updated to the latest available version which can be found with the sdkmanager --list --include_obsolete. sdkmanager can be found in your commandline-tools package of the android sdk. Additionally, set the ANDROID_SDK_ROOT environment variable to your local Android SDK installation.

The script must be run on a Linux or Mac host. Run:

`$ cd tools/android-sdk && ./create_cipd_packages.sh <new_version_tag> <path_to_your_local_android_sdk>`

This script will download and re-upload the entire SDK, so it may take a long time to complete. cmdline-tools should be installed in your local SDK as the script uses sdkmanager. Once the CIPD packages are finished uploading, you can update the SDK version tag used in .ci.yaml, DEPS, and elsewhere as described below.

It is no longer recommended to upload CIPD Android SDK packages manually, but if it must be done, run the following commands to zip and upload each package to CIPD:

`$ cipd create -in <your-android-dir>/Android/sdk/<some_package> -name flutter/android/sdk/<some_package> -tag version:<new-version-tag>`

Typically, <your-android-dir> is in your home directory under ~/Library/Android. The <new-version-tag> is what you will use to specify the new package you uploaded in the Flutter engine DEPS file.

Update the Engine: ​

Update the compile and target SDK versions we use ​

Modify the following files as described:

• DEPS: Roll buildroot hash to that of the PR you used to update the buildroot
• DEPS: Change the version parameter under flutter/android/sdk/all/$ to the newly uploaded CIPD version tag, e.g. 'version': 'version:30r2'
• tools/javadoc/gen_javadoc.py: Bump the reference to android-XX in classpath to the latest version.
• tools/cipd/android_embedding_bundle/build.gradle: Bump compileSdkVersion XX to the latest version.
• shell/platform/android/test_runner/build.gradle: Bump compileSdkVersion XX to the latest version.
• shell/platform/android/AndroidManifest.xml: Bump android:targetSdkVersion=XX to the latest version.
• testing/android/native_activity/native_activity.gni: Bump the reference to build-tools/XX in android_buildtools to the latest build-tools version and the reference to android-XX in android_jar to the latest version.
• testing/scenario_app/android/app/build.gradle: Upgrade buildToolsVersion to the latest build-tools version and the compileSdkVersion and targetSdkVersion to the latest version.
• In all other android projects in testing: Upgrade the compileSdkVersion and targetSdkVersion in android/app/build.gradle.

This list may become outdated, so be sure to change any references to the old SDK version to the latest version in build.gradle files across the repo.

Update our android_virtual_device dependency ​

1. Locate the desired Android Virtual Device (AVD) from https://chrome-infra-packages.appspot.com/p/chromium/tools/android/avd/linux-amd64/. You should look at the most recently updated AVD and verify that it has the desired generic_android<API#>.textpb for the API version that you are modifying the engine to support. Then, determine its build_id number by clicking on the AVD instance you would like to use and looking for the build_id tag.
2. In each of the engine builders (at the time of writing: ci/builders/linux_android_emulator_skia.json & ci/builders/linux_android_emulator.json), find the android_virtual_device and avd_cipd_version depedency entries and update them to the versions you desire, e.g.

{
    "dependency": "android_virtual_device",
    "version": "android_<API#>_google_apis_x64.textpb"
},
{
    "dependency": "avd_cipd_version",
    "version": "build_id:<build_id>"
}

Next Steps: Update the Framework, Examples and Samples ​

• Templates in the framework: Change targetSdkVersion in various build.gradle.tmpl files to use the new API version
• Examples and samples: Change targetSdkVersion in android/app/build.gradle for each project to the new API version.