Set up your environment - Android

These instructions explain how to set up Cobalt for your workstation and Android device. The package being built here is referred to as CoAT (Cobalt on Android TV).

Preliminary Setup

  1. Download 'depot_tools', which is used to build the Cobalt code. An easy option is to put them in ~/depot_tools. Clone the tools, by running the following command:

    cd ~/
    git clone
  2. Add your 'depot_tools' directory to the end of your PATH variable. We recommend adding something like this to your .bashrc or .profile file:

  3. Download and install Android Studio.

  4. Run cobalt/build/gyp_cobalt android-x86 to configure the Cobalt build, which also installs the SDK and NDK. (This step will have to be repeated with 'android-arm' or 'android-arm64' to target those architectures.) The SDK and NDK will be downloaded and installed into a starboard-toolchains directory as needed. If prompted, read and accept the license agreement to proceed forward.

    Note: If you have trouble building with an error referencing the debug.keystore you may need to set one up on your system:

    keytool -genkey -v -keystore ~/.android/debug.keystore -storepass android -alias androiddebugkey -keypass android -keyalg RSA -keysize 2048 -validity 10000

Setup your device

Configure your device to be in developer mode:

  1. From Settings, in the Device row, select About.
  2. Scroll down to and click on Build several times until a toast appears with the message, "You are now a developer."
  3. In the newly added "developer options" settings menu, make sure USB debugging is enabled.

Setup your workstation environment

For manually installing Android Studio and the SDK.

Note: Instructions moving forward are assuming a Linux environment.

  1. Complete the Preliminary Setup above.
  2. Launch Android Studio.
  3. Android Studio may still prompt to install an SDK if this is the very first time you've run it. Go ahead and click 'yes' to open the SDK manager to install the following:
    • Edit "Android SDK location" and set the path to: $HOME/starboard-toolchains/AndroidSdk
      • NOTE: We use the same SDK for the IDE and the gyp/ninja build. This directory will already exist since you've already run gyp_cobalt for an android target, so you'll see a warning in the setup wizard that an SDK was detected, which is okay.
        • The path may also be $HOME/cobalt-toolchains/AndroidSdk if you previously had an older environment configured on your machine - this is okay.
      • Select both Android SDK and Android SDK Platform (whatever current version is presented should be fine)
    • On the SDK Platforms tab select:
      • Android API 28 (or whatever was already installed by default)
    • On the "SDK Tools" tab select (most of these should already be installed since you already ran gyp):
      1. Android SDK Build-Tools (e.g. 28.0.3)
      2. CMake
      3. LLDB
      4. Android Emulator
      5. Android SDK Platform-Tools
      6. Android SDK Tools
      7. NDK
      8. Support Repository > Android Support Repository
      9. Support Repository > Google Repository
  4. At the welcome screen, choose to open an existing Android Studio project, and choose the project in your Cobalt repo at starboard/android/apk (just select the directory). This is "coat" (Cobalt On Android TV).
    • NOTE: Do not let it update the 'Android Gradle Plugin' if it prompts for that, use the 'Don't remind me again' button. If you inadvertently let it upgrade, you can just revert the change to build.gradle in your git repo.
  5. You may see a popup "Unregistered VCS roots detected" indicating that it has detected the cobalt git repo. If you want to use git integration in Android Studio, you can add the roots, or if not then choose to ignore them.
  6. If you didn't already get prompted to install the SDK, do it now by going to Tools -> SDK Manager (or ) on the toolbar) and making the same choices as shown in step 4.
  7. Make a new virtual device (= emulator) via Tools -> AVD Manager (or on the toolbar).
    • Category: TV -> Android TV (720p)
    • System image: Pie (API 28) x86 (you'll have to download the image) (The code should work on any API 21+, but there's a bug in the emulator preventing API 21 from working, but it does work on API 21 hardware)
    • You may be prompted to install some Intel virtualization drivers and/or change some BIOS settings to enable it, which will require you to reboot your machine.
  8. Run this AVD device. You can keep it running. Remember to restart it if your machine reboots. (Or you can start it when prompted for the target device if launching the app from Android Studio.)

Basic Build, Install, and Run (command-line based)

  1. Complete the Preliminary Setup above
  2. Generate the cobalt.apk by building the "cobalt_deploy" target

    ninja -C out/android-x86_gold cobalt_deploy

    Output can be found in the corresponding out/android-x86_gold directory.

    Note: If you have trouble building with an error referencing the debug.keystore you may need to set one up on your system:

    keytool -genkey -v -keystore ~/.android/debug.keystore -storepass android -alias androiddebugkey -keypass android -keyalg RSA -keysize 2048 -validity 10000
  3. Install the resulting APK into your test device with adb:

    adb install out/android-x86_gold/cobalt.apk
  4. Start the application with:

    adb shell am start dev.cobalt.coat/
  5. For command line parameters use the --esa flag to specify the "args" array as comma-separated values (with characters backslash-escaped as needed to make it through both the shell on your workstation and the shell on the device), e.g.:

    adb shell am start --esa args --flag_arg --value_arg=something dev.cobalt.coat
  6. To monitor log output, watch logcat in another shell with a filter for starboard messages:

    adb logcat -s starboard:*
  7. To kill any existing running application process (even if it's no longer the active app) use:

    adb shell am force-stop dev.cobalt.coat

Building/running/debugging (Android Studio IDE)

  1. Manually run cobalt/build/gyp_cobalt android-x86 in a shell. (You should do this after each time you sync your repo)
  2. From the initial setup above, you should have opened the Android Studio project checked in at starboard/android/apk.
  3. In the sidebar on the left, you should see app appear as bolded top-level item. If you don't see this, restart Android Studio.
  4. If you didn't install your Cobalt depot_tools in the standard location ($HOME/depot_tools), then make starboard/android/apk/app/.cobaltrc and set the DEPOT_TOOLS envvar to the path to where you installed them (or make a symlink in the standard location to where you have them).
  5. To run the app and attach the debugger: Run -> Debug 'app' (or in the toolbar)
  6. If it's taking awhile, it's probably the ninja build. You can see that it is still processing by looking for a rotating spinner labeled "Gradle Build Running" on the bottom bar.

    Note: If you have trouble building with an error referencing the debug.keystore you may need to set one up on your system:

    keytool -genkey -v -keystore ~/.android/debug.keystore -storepass android -alias androiddebugkey -keypass android -keyalg RSA -keysize 2048 -validity 10000
  7. To add command line parameters add --esa to specify the "args" array as comma-separated values (with characters like '&' backslash-escaped to make it through the launch command) under:

    Run -> Edit Configurations… -> "app" -> General -> Launch Options -> Launch Flags

    e.g. To run with a different URL: --esa args --url=<DIFFERENT_URL>

  8. To monitor log output, see the Logcat on the bottom-left of the IDE. You can enter "starboard" in the search bubble to filter the output.

  9. To kill the app go to Run -> Stop, or click the red square stop button either on the top toolbar, or in the debugger on the bottom-left of the IDE.

  10. To set breakpoints in native code, just open the relevant source file with File -> Open… (sorry, files outside the apk project can't appear in the Project panel of the IDE) and click in the gutter of the relevant line. (Once you have one C++ file open, the path breadcrumbs at the top are useful to open other nearby files.)

Running Tests

The test target itself (e.g. nplb) just builds an .so file (e.g. To run that on a device, it needs to be packaged into an APK, which is done by the associated "deploy" target (e.g. nplb_deploy). The Starboard test runner does all this for you, so just use that to build and run tests. For example, to build and run "devel" NPLB on an ARM64 device, from the top 'src' directory:

starboard/tools/testing/ -p android-arm64 -c devel -b -r -t nplb

If you want to debug a test, you can run it from Android Studio. Edit build.gradle in the 'app' module (not to the one in the top 'apk' module) to change DEFAULT_COBALT_TARGET to be the name of the test you want to debug instead of 'cobalt'. Then you can set breakpoints, etc. in the test the same as when debugging Cobalt.

Removing the Cobalt Android Environment

  1. Unset ANDROID_HOME and or ANDROID_NDK_HOME in your shell and in .bashrc
  2. Delete the SDK:

    rm -rf ~/starboard-toolchains/AndroidSdk
  3. Delete NDK toolchains:

    rm -rf  ~/starboard-toolchains/android*
  4. Delete cached Android files:

    rm -rf ~/.android

    NOTE: Removing this directory will remove all signing keys even for different projects, so only delete this if you truly want to remove the entire Cobalt and Android Studio environment.