Unity/C# button callback utility to initiate APK download and installation on Meta Quest devices.

APKDownloader.cs

using System.Collections;
using System.IO;
using UnityEngine;
using UnityEngine.Networking;

public class ApkDownloaderInstaller : MonoBehaviour
{
    // Replace this with your real APK link (must be direct download)
    private const string ApkUrl = "https://github.com/Igalia/wolvic/releases/download/v1.8.2/Wolvic-oculusvr-arm64-gecko-metaStore-release.apk";
    private string localPath;

    // Called by your UI Button
    public void OnInstallButton()
    {
        StartCoroutine(DownloadAndInstall());
    }

    private IEnumerator DownloadAndInstall()
    {
        localPath = Path.Combine(Application.persistentDataPath, "MyApp.apk");
        Debug.Log($"[Installer] Downloading to: {localPath}");

        if (File.Exists(localPath))
            File.Delete(localPath);

        using (UnityWebRequest www = UnityWebRequest.Get(ApkUrl))
        {
            www.downloadHandler = new DownloadHandlerFile(localPath);
            yield return www.SendWebRequest();

            if (www.result != UnityWebRequest.Result.Success)
            {
                Debug.LogError("[Installer] Download failed: " + www.error);
                yield break;
            }
        }

        Debug.Log("[Installer] Download complete. Launching installer...");

#if UNITY_ANDROID && !UNITY_EDITOR
        TryInstallApk(localPath);
#else
        Debug.LogWarning("[Installer] Only works on Android device.");
#endif
    }

#if UNITY_ANDROID && !UNITY_EDITOR
    private void TryInstallApk(string apkPath)
    {
        using (var unityPlayer = new AndroidJavaClass("com.unity3d.player.UnityPlayer"))
        using (var currentActivity = unityPlayer.GetStatic<AndroidJavaObject>("currentActivity"))
        {
            try
            {
                // ---- STEP 1: Get File URI via FileProvider ----
                var file = new AndroidJavaObject("java.io.File", apkPath);
                var fileProvider = new AndroidJavaClass("androidx.core.content.FileProvider");
                var uri = fileProvider.CallStatic<AndroidJavaObject>(
                    "getUriForFile",
                    currentActivity,
                    currentActivity.Call<string>("getPackageName") + ".provider",
                    file
                );

                // ---- STEP 2: Build install Intent ----
                var intent = new AndroidJavaObject("android.content.Intent", "android.intent.action.VIEW");
                intent.Call<AndroidJavaObject>("setDataAndType", uri, "application/vnd.android.package-archive");

                int FLAG_GRANT_READ_URI_PERMISSION = 1;
                int FLAG_ACTIVITY_NEW_TASK = 0x10000000;
                intent.Call<AndroidJavaObject>("addFlags", FLAG_GRANT_READ_URI_PERMISSION);
                intent.Call<AndroidJavaObject>("addFlags", FLAG_ACTIVITY_NEW_TASK);

                // ---- STEP 3: Request permission if needed ----
                bool canInstall = false;
                int sdkInt = new AndroidJavaClass("android.os.Build$VERSION").GetStatic<int>("SDK_INT");

                if (sdkInt >= 26)
                {
                    var pkgManager = currentActivity.Call<AndroidJavaObject>("getPackageManager");
                    canInstall = pkgManager.Call<bool>("canRequestPackageInstalls");
                    if (!canInstall)
                    {
                        // open settings to grant permission
                        var settingsIntent = new AndroidJavaObject(
                            "android.content.Intent",
                            "android.settings.MANAGE_UNKNOWN_APP_SOURCES"
                        );

                        var uriClass = new AndroidJavaClass("android.net.Uri");
                        var pkgUri = uriClass.CallStatic<AndroidJavaObject>(
                            "parse",
                            "package:" + currentActivity.Call<string>("getPackageName")
                        );
                        settingsIntent.Call<AndroidJavaObject>("setData", pkgUri);
                        settingsIntent.Call<AndroidJavaObject>("addFlags", FLAG_ACTIVITY_NEW_TASK);
                        currentActivity.Call("startActivity", settingsIntent);
                        Debug.LogWarning("[Installer] Please enable 'Install unknown apps' and press the button again.");
                        return;
                    }
                }

                // ---- STEP 4: Launch the installer ----
                currentActivity.Call("startActivity", intent);
                Debug.Log("[Installer] Installer launched.");
            }
            catch (AndroidJavaException e)
            {
                Debug.LogError("[Installer] Exception: " + e.Message);
            }
        }
    }
#endif
}