mediapipe/docs/getting_started/android.md

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MediaPipe on Android

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Please follow instructions below to build Android example apps in the supported MediaPipe solutions. To learn more about these example apps, start from Hello World! on Android. To incorporate MediaPipe into an existing Android Studio project, see these instructions that use Android Archive (AAR) and Gradle.

Building Android example apps

Prerequisite

• Install MediaPipe following these instructions.
• Setup Java Runtime.
• Setup Android SDK release 28.0.3 and above.
• Setup Android NDK version between 18 and 21.

MediaPipe recommends setting up Android SDK and NDK via Android Studio (and see below for Android Studio setup). However, if you prefer using MediaPipe without Android Studio, please run setup_android_sdk_and_ndk.sh to download and setup Android SDK and NDK before building any Android example apps.

If Android SDK and NDK are already installed (e.g., by Android Studio), set $ANDROID_HOME and $ANDROID_NDK_HOME to point to the installed SDK and NDK.

export ANDROID_HOME=<path to the Android SDK>
export ANDROID_NDK_HOME=<path to the Android NDK>

In order to use MediaPipe on earlier Android versions, MediaPipe needs to switch to a lower Android API level. You can achieve this by specifying api_level = $YOUR_INTENDED_API_LEVEL in android_ndk_repository() and/or android_sdk_repository() in the WORKSPACE file.

Please verify all the necessary packages are installed.

• Android SDK Platform API Level 28 or 29
• Android SDK Build-Tools 28 or 29
• Android SDK Platform-Tools 28 or 29
• Android SDK Tools 26.1.1
• Android NDK 19c or above

Option 1: Build with Bazel in Command Line

Tip: You can run this script to build (and install) all MediaPipe Android example apps.

1. To build an Android example app, build against the corresponding android_binary build target. For instance, for MediaPipe Hands the target is handtrackinggpu in the BUILD file:

   Note: To reduce the binary size, consider appending --linkopt="-s" to the command below to strip symbols.

   bazel build -c opt --config=android_arm64 mediapipe/examples/android/src/java/com/google/mediapipe/apps/handtrackinggpu:handtrackinggpu
   

2. Install it on a device with:

   adb install bazel-bin/mediapipe/examples/android/src/java/com/google/mediapipe/apps/handtrackinggpu/handtrackinggpu.apk
   

Option 2: Build with Bazel in Android Studio

The MediaPipe project can be imported into Android Studio using the Bazel plugins. This allows the MediaPipe examples to be built and modified in Android Studio.

To incorporate MediaPipe into an existing Android Studio project, see these instructions that use Android Archive (AAR) and Gradle.

The steps below use Android Studio 3.5 to build and install a MediaPipe example app:

1. Install and launch Android Studio 3.5.

2. Select Configure -> SDK Manager -> SDK Platforms.

   • Verify that Android SDK Platform API Level 28 or 29 is installed.
   • Take note of the Android SDK Location, e.g., /usr/local/home/Android/Sdk.

3. Select Configure -> SDK Manager -> SDK Tools.

   • Verify that Android SDK Build-Tools 28 or 29 is installed.
   • Verify that Android SDK Platform-Tools 28 or 29 is installed.
   • Verify that Android SDK Tools 26.1.1 is installed.
   • Verify that Android NDK 19c or above is installed.
   • Take note of the Android NDK Location, e.g., /usr/local/home/Android/Sdk/ndk-bundle or /usr/local/home/Android/Sdk/ndk/20.0.5594570.

4. Set environment variables $ANDROID_HOME and $ANDROID_NDK_HOME to point to the installed SDK and NDK.

   export ANDROID_HOME=/usr/local/home/Android/Sdk
   
   # If the NDK libraries are installed by a previous version of Android Studio, do
   export ANDROID_NDK_HOME=/usr/local/home/Android/Sdk/ndk-bundle
   # If the NDK libraries are installed by Android Studio 3.5, do
   export ANDROID_NDK_HOME=/usr/local/home/Android/Sdk/ndk/<version number>
   

5. Select Configure -> Plugins to install Bazel.

6. On Linux, select File -> Settings -> Bazel settings. On macos, select Android Studio -> Preferences -> Bazel settings. Then, modify Bazel binary location to be the same as the output of $ which bazel.

7. Select Import Bazel Project.

   • Select Workspace: /path/to/mediapipe and select Next.
   • Select Generate from BUILD file: /path/to/mediapipe/BUILD and select Next.
   • Modify Project View to be the following and select Finish.

   directories:
     # read project settings, e.g., .bazelrc
     .
     -mediapipe/objc
     -mediapipe/examples/ios
   
   targets:
     //mediapipe/examples/android/...:all
     //mediapipe/java/...:all
   
   android_sdk_platform: android-29
   
   sync_flags:
     --host_crosstool_top=@bazel_tools//tools/cpp:toolchain
   

8. Select Bazel -> Sync -> Sync project with Build files.

   Note: Even after doing step 4, if you still see the error: "no such package '@androidsdk//': Either the path attribute of android_sdk_repository or the ANDROID_HOME environment variable must be set.", please modify the WORKSPACE file to point to your SDK and NDK library locations, as below:

   android_sdk_repository(
       name = "androidsdk",
       path = "/path/to/android/sdk"
   )
   
   android_ndk_repository(
       name = "androidndk",
       path = "/path/to/android/ndk"
   )
   

9. Connect an Android device to the workstation.

10. Select Run... -> Edit Configurations....

    • Select Templates -> Bazel Command.
    • Enter Target Expression: //mediapipe/examples/android/src/java/com/google/mediapipe/apps/handtrackinggpu:handtrackinggpu
    • Enter Bazel command: mobile-install.
    • Enter Bazel flags: -c opt --config=android_arm64.
    • Press the [+] button to add the new configuration.
    • Select Run to run the example app on the connected Android device.