Hi,
I am trying to solve unexpected problems when using MAUI application on Magic Leap 2 OS 1.6.0.
I prepared a minimalist demo to check the possibility of using Magic Leap 2 for our business, but I couldn't find a working constellation for ML2.
In order to eliminate third-party inadequacy, I used two different NuGet packages for working with OpenXR: Evergine and Silk.NET.
I don't get any data from OpenXR for this manifest on Android (On Windows 11 I got 24 items):
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
<application android:allowBackup="true" android:supportsRtl="true">
<!-- Our activity is the built-in NativeActivity framework class.
This will take care of integrating with our NDK code. -->
<activity android:name="android.app.NativeActivity"
android:configChanges="orientation|keyboardHidden"
android:launchMode="singleTask"
android:exported="true">
<!-- Tell NativeActivity the name of our .so -->
<!-- Java.Lang.RuntimeException <meta-data android:name="android.app.lib_name" android:value="hand_tracking" />-->
<!--<intent-filter>
<action android:name="android.intent.action.MAIN" />
--><!-- Display the application on the home launcher --><!--
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.LAUNCHER" />
--><!-- This category is defined by the OpenXR specification and is required for all OpenXR applications that run on HMD devices --><!--
<category android:name="org.khronos.openxr.intent.category.IMMERSIVE_HMD" />
</intent-filter>-->
</activity>
</application>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="org.khronos.openxr.permission.OPENXR_SYSTEM" />
<uses-permission android:name="com.magicleap.permission.HAND_TRACKING" />
<!-- Specify the requested API Level -->
<!--<uses-feature android:name="com.magicleap.api_level" android:version="20" />-->
<uses-sdk />
</manifest>
I don't get a working app for this manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android">
<application android:allowBackup="true" android:supportsRtl="true">
<!-- Our activity is the built-in NativeActivity framework class.
This will take care of integrating with our NDK code. -->
<activity android:name="android.app.NativeActivity"
android:configChanges="orientation|keyboardHidden"
android:launchMode="singleTask"
android:exported="true">
<!-- Tell NativeActivity the name of our .so -->
<meta-data android:name="android.app.lib_name" android:value="hand_tracking" />
<intent-filter>
<action android:name="android.intent.action.MAIN" />
Display the application on the home launcher
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.LAUNCHER" />
This category is defined by the OpenXR specification and is required for all OpenXR applications that run on HMD devices
<category android:name="org.khronos.openxr.intent.category.IMMERSIVE_HMD" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="org.khronos.openxr.permission.OPENXR_SYSTEM" />
<uses-permission android:name="com.magicleap.permission.HAND_TRACKING" />
<!-- Specify the requested API Level -->
<uses-feature android:name="com.magicleap.api_level" android:version="20" />
<uses-sdk />
</manifest>
In this second case I get an exception:
Java.Lang.RuntimeException
Message=Unable to start activity ComponentInfo{com.companyname.voyager2maui/android.app.NativeActivity}: java.lang.IllegalArgumentException: Unable to find native library main using classloader: dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.companyname.voyager2maui-dE9idSzyNW4_Sm6Pav5rTA==/base.apk"],nativeLibraryDirectories=[/data/app/com.companyname.voyager2maui-dE9idSzyNW4_Sm6Pav5rTA==/lib/x86_64, /data/app/com.companyname.voyager2maui-dE9idSzyNW4_Sm6Pav5rTA==/base.apk!/lib/x86_64, /system/lib64, /system/product/lib64, /vendor/lib64]]]
Creating an application is simple, based on the basic MAUI application in Visual Studio 2022.
Make sure you have installed all necessary components in the installer for your Studio, such as ".NET MAUI SDK Windows" and "Android SDK setup"...
In Visual Studio, use Create new Project and search for .NET MAUI App.
Add NuGet packages to the project:
Evergine.OpenXR
OpenXR.Loader
Silk.NET.OpenXR
Silk.NET.OpenXR.Extensions.KHR
Silk.NET.OpenXR.Extensions.MAGICLEAP
Silk.NET.OpenXR.Extensions.MSFT
In Properties of the project go to the Build and select Allow Unsafe code.
In the root of the project add file "libopenxr_loader.so".
You can get this file from the web
from file hello_xr-Vulkan-release-1.1.36.apk
if you rename it to the ZIP file and get the file from archive path \lib\x86_64.
In the project in the file "MainPage.xaml.cs" change the code to:
Add:
using Evergine.Bindings.OpenXR;
using Silk.NET.OpenXR;
Overvrite:
public partial class MainPage : ContentPage
{
public MainPage()
{
InitializeComponent();
}
private void OnCounterClicked(object sender, EventArgs e)
{
(uint evergineCount, uint silkCount) = GetExtensionProperties();
CounterBtn.Text = $"Evergine: {evergineCount}, Silk.NET: {silkCount}";
SemanticScreenReader.Announce(CounterBtn.Text);
}
private (uint evergineCount, uint silkCount) GetExtensionProperties()
{
// Evergine:
uint evergineCount;
unsafe
{
_ = OpenXRNative.xrEnumerateInstanceExtensionProperties(null, 0, &evergineCount, null);
}
// Silk.NET
XR xrApi = XR.GetApi();
uint silkCount = 0;
unsafe
{
_ = xrApi.EnumerateInstanceExtensionProperties((byte*)null, 0, &silkCount, null);
}
return (evergineCount, silkCount);
}
}
Source for Android Manifest changes:
I think this website is missing information about parameter.
android:exported="true"
If you run the application on Windows 11 and click the button in the application, the name of the button will change to Evergine: 24, Silk.NET: 24.
I couldn't find a working form of the AndroidManifest.xml file, either the app runs but doesn't return any OpenXR properties, or it throws an exception.
Actually, you don't have to worry about what I describe in this problem, just create a working example application in MAUI and describe it in the documentation or put it on GitHub.
Thank you very much, Magic Leap is a very interesting device, I would recommend you to make Magic Leap 3 one that combines the advantages of Magic Leap 2 and HoloLens 2, this will give you the best device on the market for clear AR 
(HoloLens 2, Vision Pro and Magic Leap 2 are on my desk.)
