Use custom manifest file and permission in Unity?

As of Unity 2018, you must implement an interface IPostGenerateGradleAndroidProject

that will allow you to edit the android manifest after Unity has created it. In the code below, I've added methods to set microphone resolution, hardware acceleration, and set the app theme (replace SetMicrophonePermission()

with your preferred method that's called when Unity calls OnPostGenerateGradleAndroidProject()

).

Add the following code to Assets/Editor/ModifyUnityAndroidAppManifestSample.cs

using System.IO;
using System.Text;
using System.Xml;
using UnityEditor.Android;

public class ModifyUnityAndroidAppManifestSample : IPostGenerateGradleAndroidProject
{

    public void OnPostGenerateGradleAndroidProject(string basePath)
    {
        // If needed, add condition checks on whether you need to run the modification routine.
        // For example, specific configuration/app options enabled

        var androidManifest = new AndroidManifest(GetManifestPath(basePath));

        androidManifest.SetMicrophonePermission();

        // Add your XML manipulation routines

        androidManifest.Save();
    }

    public int callbackOrder { get { return 1; } }

    private string _manifestFilePath;

    private string GetManifestPath(string basePath)
    {
        if (string.IsNullOrEmpty(_manifestFilePath))
        {
            var pathBuilder = new StringBuilder(basePath);
            pathBuilder.Append(Path.DirectorySeparatorChar).Append("src");
            pathBuilder.Append(Path.DirectorySeparatorChar).Append("main");
            pathBuilder.Append(Path.DirectorySeparatorChar).Append("AndroidManifest.xml");
            _manifestFilePath = pathBuilder.ToString();
        }
        return _manifestFilePath;
    }
}


internal class AndroidXmlDocument : XmlDocument
{
    private string m_Path;
    protected XmlNamespaceManager nsMgr;
    public readonly string AndroidXmlNamespace = "http://schemas.android.com/apk/res/android";
    public AndroidXmlDocument(string path)
    {
        m_Path = path;
        using (var reader = new XmlTextReader(m_Path))
        {
            reader.Read();
            Load(reader);
        }
        nsMgr = new XmlNamespaceManager(NameTable);
        nsMgr.AddNamespace("android", AndroidXmlNamespace);
    }

    public string Save()
    {
        return SaveAs(m_Path);
    }

    public string SaveAs(string path)
    {
        using (var writer = new XmlTextWriter(path, new UTF8Encoding(false)))
        {
            writer.Formatting = Formatting.Indented;
            Save(writer);
        }
        return path;
    }
}


internal class AndroidManifest : AndroidXmlDocument
{
    private readonly XmlElement ApplicationElement;

    public AndroidManifest(string path) : base(path)
    {
        ApplicationElement = SelectSingleNode("/manifest/application") as XmlElement;
    }

    private XmlAttribute CreateAndroidAttribute(string key, string value)
    {
        XmlAttribute attr = CreateAttribute("android", key, AndroidXmlNamespace);
        attr.Value = value;
        return attr;
    }

    internal XmlNode GetActivityWithLaunchIntent()
    {
        return SelectSingleNode("/manifest/application/activity[intent-filter/action/@android:name='android.intent.action.MAIN' and " +
                "intent-filter/category/@android:name='android.intent.category.LAUNCHER']", nsMgr);
    }

    internal void SetApplicationTheme(string appTheme)
    {
        ApplicationElement.Attributes.Append(CreateAndroidAttribute("theme", appTheme));
    }

    internal void SetStartingActivityName(string activityName)
    {
        GetActivityWithLaunchIntent().Attributes.Append(CreateAndroidAttribute("name", activityName));
    }


    internal void SetHardwareAcceleration()
    {
        GetActivityWithLaunchIntent().Attributes.Append(CreateAndroidAttribute("hardwareAccelerated", "true"));
    }

    internal void SetMicrophonePermission()
    {
        var manifest = SelectSingleNode("/manifest");
        XmlElement child = CreateElement("uses-permission");
        manifest.AppendChild(child);
        XmlAttribute newAttribute = CreateAndroidAttribute("name", "android.permission.RECORD_AUDIO");
        child.Attributes.Append(newAttribute);
    }
}