com.unity.uiwidgets/com.unity.uiwidgets/Runtime/engine2/AndroidPlatformUtil.cs

#if !UNITY_EDITOR && UNITY_ANDROID
using UnityEngine;
using AOT;
using System;
using System.IO;
using System.Runtime.InteropServices;
using NativeBindings = Unity.UIWidgets.ui.NativeBindings;
namespace Unity.UIWidgets.engine2 {
    public static class AndroidPlatformUtil {
        [DllImport(NativeBindings.dllName)]
        internal static extern void InitUnpackFile(UnpackFileCallback unpack);

        internal delegate string UnpackFileCallback(string file);

        [MonoPInvokeCallback(typeof(UnpackFileCallback))]
        internal static string unpackFile(string file) {
            var dir = Application.temporaryCachePath + "/";
            if (!File.Exists(dir + file)) {
                WWW unpackerWWW = new WWW("jar:file://" + Application.dataPath + "!/assets/" + file);
                while (!unpackerWWW.isDone) {
                } // This will block in the webplayer.

                if (!string.IsNullOrEmpty(unpackerWWW.error)) {
                    Debug.Log("Error unpacking 'jar:file://" + Application.dataPath + "!/assets/" + file +
                              "'");
                    dir = "";
                    return dir + file;
                }
                System.IO.FileInfo fileInfo = new System.IO.FileInfo(dir + file);
                fileInfo.Directory.Create();
                System.IO.File.WriteAllBytes(fileInfo.FullName,  unpackerWWW.bytes);
            }

            return dir + file;
        }
        
        [DllImport(NativeBindings.dllName)]
        static extern System.IntPtr GetUnityContextEventFunc();

        public static void Init() {
            InitUnpackFile(unpackFile);
            GL.IssuePluginEvent(GetUnityContextEventFunc(), 1);
        }
    }
}
#endif