Enable AR in your Android NDK app

Enable AR to use augmented reality features in your new or existing app.

Configure your app to be AR Required or AR Optional

To save space on individual devices, all AR features are stored in an app called Google Play Services for AR that is updated separately by the Play Store. Android apps that use AR features communicate with Google Play Services for AR using the ARCore SDK. An app that supports AR features can be configured in two ways: AR Required and AR Optional. This designation determines how the app interacts with the Google Play Services for AR app.

An AR Required app cannot function without ARCore. It requires an ARCore supported device that has installed Google Play Services for AR.

• The Google Play Store will only make AR Required apps available on devices that support ARCore.
• When users install an AR Required app, the Google Play Store will automatically install Google Play Services for AR on their device. However, your app must still perform additional runtime checks in case Google Play Services for AR is out of date or has been manually uninstalled.

An AR Optional app uses ARCore to enhance existing functionality. It has optional AR features which are only activated on ARCore supported devices that have installed Google Play Services for AR.

• AR Optional apps can be installed and run on devices that don’t support ARCore.
• When users install an AR Optional app, the Google Play Store will not automatically install Google Play Services for AR on the device.

To make your app AR Required or AR Optional, update your AndroidManifest.xml to include the following entries:

<uses-permission android:name="android.permission.CAMERA" />

<!-- Limits app visibility in the Google Play Store to ARCore supported devices
     (https://developers.google.com/ar/devices). -->
<uses-feature android:name="android.hardware.camera.ar" />

<application …>
    …

    <!-- "AR Required" app, requires "Google Play Services for AR" (ARCore)
         to be installed, as the app does not include any non-AR features. -->
    <meta-data android:name="com.google.ar.core" android:value="required" />
</application>

<uses-permission android:name="android.permission.CAMERA" />

<!-- If your app was previously AR Required, don't forget to remove the
     `<uses-feature android:name="android.hardware.camera.ar" />` entry, as
     this would limit app visibility in the Google Play Store to only
     ARCore supported devices. -->

<application …>
    …

    <!-- "AR Optional" app, contains non-AR features that can be used when
         "Google Play Services for AR" (ARCore) is not available. -->
    <meta-data android:name="com.google.ar.core" android:value="optional" />
</application>

Then, modify your app's build.gradle to specify a minSdkVersion of at least 24:

 android {
     defaultConfig {
         …
         minSdkVersion 24
     }
 }

Add build dependencies

1. Make sure your project's build.gradle file includes Google's Maven repository.

   allprojects {
       repositories {
           google()
           …
       }
   }
   

2. Add a custom task to your module's build.gradle file to extract included native libraries from the ARCore AAR file. This way, they can be referenced directly in a C or C++ project.

3. In the app/build directory, define a variable to the directory where the native libraries will be extracted to.

4. Create a Gradle configuration to hold the data and extraction tasks.

   /*
   The ARCore AAR library contains native shared libraries that are
   extracted before building to a temporary directory.
   */
   def arcore_libpath = "${buildDir}/arcore-native"
   
   // Create a configuration to mark which aars to extract .so files from
   configurations { natives }
   

5. Create a task to copy the native libraries from the AAR file, and add it to the build dependencies.

   // Extracts the shared libraries from AARs in the native configuration
   // so that NDK builds can access these libraries.
   task extractNativeLibraries() {
      // Extract every time.
      outputs.upToDateWhen { false }
   
      doFirst {
           configurations.natives.files.each { f ->
               copy {
                   from zipTree(f)
                   into arcore_libpath
                   include "jni/**/*"
               }
           }
       }
   }
   
   tasks.whenTaskAdded {
       task-> if (task.name.contains("external") && !task.name.contains("Clean")) {
           task.dependsOn(extractNativeLibraries)
       }
   }
   

6. Configure the native build flags to pass the locations to the external build tools.

   // From the sample app.
   externalNativeBuild {
       cmake {
           cppFlags "-std=c++11", "-Wall"
           arguments "-DANDROID_STL=c++_static",
                   "-DARCORE_LIBPATH=${arcore_libpath}/jni",
                   "-DARCORE_INCLUDE=${project.rootDir}/../../libraries/include"
       }
   }
   

7. Add the dependencies for both the Java and the native libraries.

   dependencies {
        ...
        // Add Java and native dependencies to the ARCore library.
        implementation 'com.google.ar:core:1.33.0'
        natives 'com.google.ar:core:1.33.0'
        ...
   }
   

8. Reference the native libraries in CMakeLists.txt.

   # Import the ARCore library.
   add_library(arcore SHARED IMPORTED)
   set_target_properties(arcore PROPERTIES IMPORTED_LOCATION
                 ${ARCORE_LIBPATH}/${ANDROID_ABI}/libarcore_sdk_c.so
                 INTERFACE_INCLUDE_DIRECTORIES ${ARCORE_INCLUDE}
   )
   

Perform runtime checks

During runtime, perform the following to ensure that AR features on your app run smoothly.

Check if ARCore is supported

An Android NDK app may use the Java ArCoreApk class to check compatibility and manage installation in the native C ARCore Session API. Depending on the structure of your app, this may be easier than using the ArCoreApk_ functions due to the large amount of error handling and user interface interaction involved.

void maybeEnableArButton(JNIEnv env, jobject context) {
  // Likely called from Activity.onCreate() of an activity with AR buttons.
  ArAvailability availability
  ArCoreApk_checkAvailability(env, context, &availability);
  if (availability == AR_AVAILABILITY_UNKNOWN_CHECKING) {
    // Set a timer to call maybeEnableArButton() again after about 200ms.
  }
  if (availability == AR_AVAILABILITY_SUPPORTED_NOT_INSTALLED ||
      availability == AR_AVAILABILITY_SUPPORTED_APK_TOO_OLD ||
      availability == AR_AVAILABILITY_SUPPORTED_INSTALLED) {
    // Show or enable the AR button.
  } else {
    // Hide or disable the AR button.
  }
}

ArCoreApk_checkAvailability() may need to query network resources to determine whether the device supports ARCore. During this time, it will return AR_AVAILABILITY_UNKNOWN_CHECKING. To reduce the perceived latency and pop-in, apps should call ArCoreApk_checkAvailability() once early in its life cycle to initiate the query, ignoring the returned value. This way, a cached result will be available immediately when an AR-entering UI element might be displayed.

Check if Google Play Services for AR is installed

Both AR Required and AR Optional apps must use ArCoreApk.requestInstall() before creating an ARCore session to check whether a compatible version of Google Play Services for AR is (still) installed and to ensure that all required ARCore device profile data has been downloaded.

// Tracks if an installation request has already been triggered.
bool install_requested_;

void nativeOnCreate() {
  // Do other setup here.

  install_requested_ = false;
}

void nativeOnResume(JNIEnv env, jobject activity) {
  if (ar_session_ == null) {
    bool user_requested_install = !install_requested_;

    ArInstallStatus install_status;
    // Ensure that Google Play Services for AR and ARCore device profile data are
    // installed and up to date.
    ArStatus error = ArCoreApk_requestInstall(
        env, activity, user_requested_install, &install_status);
    if (error != AR_SUCCESS) {
      // Inform user of error.
      return;
    }

    switch (install_status) {
      case AR_INSTALL_STATUS_INSTALLED:
        break;
      case AR_INSTALL_STATUS_INSTALL_REQUESTED:
        // When this method returns AR_INSTALL_STATUS_INSTALL_REQUESTED:
        // 1. This activity will be paused.
        // 2. The user is prompted to install or update Google Play
        //    Services for AR (market://details?id=com.google.ar.core).
        // 3. ARCore downloads the latest device profile data.
        // 4. This activity is resumed. The next invocation of
        //    ArCoreApk_requestInstall() will either return
        //    AR_INSTALL_STATUS_INSTALLED or throw an exception if the
        //    installation or update did not succeed.
        install_requested_ = true;
        return;
    }

    // Request camera permissions.

    error = ArSession_create(env, context, &ar_session_);
    if (error != AR_SUCCESS) {
      // Inform user of error.
      return;
    }

    // Configure the ARCore session.
  }

  // Normal onResume behavior.
}

Comply with User Privacy Requirements

To publish your app on the Play Store, make sure that your app complies with ARCore's User Privacy Requirements.

What’s next

• Learn how to configure an ARCore session.