FileWatcher.cs

using System.Collections.Generic;
using UnityEngine;
using System.IO;
using UnityEngine.Networking;
using UniRx.Async;

public class FileWatcher : MonoBehaviour
{
    static readonly string watchFolderPath = Application.streamingAssetsPath;

    [SerializeField] List<Texture> textures = new List<Texture>();
    
    FileSystemWatcher watcher;



    void Awake()
    {
        Clear();
    }

    void Start()
    {
        watcher = new FileSystemWatcher();

        watcher.Path = watchFolderPath;
        watcher.Filter = "*.jpg";
        watcher.NotifyFilter = NotifyFilters.FileName | NotifyFilters.DirectoryName | NotifyFilters.LastWrite;
        watcher.IncludeSubdirectories = false;

        watcher.Created += new FileSystemEventHandler(WatcherChanged);
        watcher.EnableRaisingEvents = true;
    }

    private void OnDestroy()
    {
        if (watcher == null) return;

        watcher.EnableRaisingEvents = false;
        watcher.Dispose();
        watcher = null;
    }

    async void WatcherChanged(System.Object _, FileSystemEventArgs e)
    {
        switch (e.ChangeType)
        {
            case WatcherChangeTypes.Created:
                Debug.Log($"File created : {e.FullPath}");

                var texture = await LoadTextureAsync(e.FullPath);

                if(texture)
                    textures.Add(texture);

                break;
        }
    }

    async UniTask<Texture> LoadTextureAsync(string url)
    {
        Debug.Log($"Load start : {url}");

        var request = UnityWebRequestTexture.GetTexture($"{url}");
        await request.SendWebRequest();

        if (request.isNetworkError || request.isHttpError)
        {
            Debug.LogError(request.error);
            return null;
        }
        else
        {
            Texture tex = DownloadHandlerTexture.GetContent(request);
            Debug.Log($"Loaded : {tex.name}");
            return tex;
        }

    }

    public void Clear()
    {
        textures.Clear();
    }
}