Can't use json file from StreamingAssets on Android and iOS

Hello, everyone. Now I'm trying to implement localization in my small project by learning from Unity Live Training.

Unity Live Training: https://www.youtube.com/watch?v=5Kt9jbnqzKA&t=50s

It works fine in editor, but when I build and test run on an Android device, it can't find the right path and replace the text with the localized one. I researched a lot on the internet and tried to fix it by myself, but sadly it didn't work. (I have 0 experience on json and streaming assets.) The following is the script in my project. I'm really not sure how to fix it. I'll appreciate it if anyone could help me. Thank you.

 void LoadLocalizedText (string fileName) {
         localizedTextDictionary = new Dictionary<string, string> ();
         string dataAsJson;
 
         #if UNITY_EDITOR
         string filePath = Path.Combine (Application.streamingAssetsPath, fileName);
 
         #elif UNITY_IOS
         string filePath = Path.Combine (Application.streamingAssetsPath + "/Raw", fileName);
 
         #elif UNITY_ANDROID
         string filePath = Path.Combine ("jar:file://" + Application.streamingAssetsPath + "!assets/", fileName);
 
         #endif
 
         if (File.Exists (filePath)) {
 
             #if  UNITY_EDITOR || UNITY_IOS
             dataAsJson = File.ReadAllText (filePath);
 
             #elif UNITY_ANDROID
             WWW reader = new WWW (filePath);
             while (!reader.isDone) {
             }
             dataAsJson = reader.text;
             #endif
 
             LocalizationData loadedData = JsonUtility.FromJson<LocalizationData> (dataAsJson);
 
             for (int i = 0; i < loadedData.items.Length; i++) {
                 localizedTextDictionary.Add (loadedData.items [i].key, loadedData.items [i].value);
             }
             Debug.Log ("Data loaded, dictionary contains: " + localizedTextDictionary.Count + " entries");
         } else {
             Debug.LogError ("Cannot find file!");
         }
         isReady = true;
     }