Share single file between many android apps (Unity)

Unity Engine
,
1

Hi,
I have two apps (this same project) with two different package names:

com.app.test1
com.app.test2

And I have two methods:

    public void AddToFile(string value)
    {
        var path = Path.Combine(URL, fileName);

        using (var fs = new FileStream(path, FileMode.Append, FileAccess.Write, FileShare.ReadWrite))
        {
            using (var sw = new StreamWriter(fs))
            {
                sw.WriteLine(value);

                Debug.Log("AddToFile!");
            }
        }

        LoadFromFile();
    }


    public void LoadFromFile()
    {
        var path = Path.Combine(URL, fileName);

        if (!File.Exists(path))
        {
            Debug.Log("File not exists!");
            return;
        }

        using (var fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
        {
            using (var sr = new StreamReader(fs))
            {
                var text = sr.ReadToEnd();
                fileValue.text = text;

                Debug.Log("LoadFromFile!");
            }
        }
    }

And everything works fine for one app. I can load file I can add some text to existing file (or create new one), but when I try to open this same file from second app I have an error:

System.UnauthorizedAccessException - "Access to the path PATH is denied"

Unity Version: 2021.3.4f1
Target platform: Android 11

I also add permissions to the android manifest (read/write).
Any sugestions?

2

to what path you are saving?

if its some public path, like downloads/ or so, i think it should work.

3

Yes, It is a public folder:

    private string URL => Path.Combine(GetAndroidInternalFilesDir(), "Download");


//I found this solution in web:
    private static string GetAndroidInternalFilesDir()
    {
        string[] potentialDirectories = new string[]
        {
        "/mnt/sdcard",
        "/sdcard",
        "/storage/sdcard0",
        "/storage/sdcard1"
        };

        if (Application.platform == RuntimePlatform.Android)
        {
            for (int i = 0; i < potentialDirectories.Length; i++)
            {
                if (Directory.Exists(potentialDirectories[i]))
                {
                    return potentialDirectories[i];
                }
            }
        }

        Debug.LogError("Path not exists!");
        return "";
    }

As I said: If I use only one app - all works fine. But when I try to open this file via second app - I just see an error.

4

ah ok, not sure then, could try the force internal or force external player settings too, if any difference.
or maybe its more strict on the recent android versions?

5

Yes, I have few more lines in code:

        if (!hasExternalStorageRead)
            Permission.RequestUserPermission(Permission.ExternalStorageRead);

        if (!hasExternalStorageWrite)
            Permission.RequestUserPermission(Permission.ExternalStorageWrite);

        if (!hasManageExternalStorage)
            Permission.RequestUserPermission("android.permission.MANAGE_EXTERNAL_STORAGE");

In Android 11, they made life and access to such files difficult. As if files are protected for only one application.

6

could also check if this plugin somehow works from multiple apps
https://github.com/yasirkula/UnityNativeFilePicker

7

This works fine, but works with copies of the file. Which also boils down to the fact that I don’t have permission to delete the file and force me to create multiple copies. Additionally: However, it forces you to manually enter the path and select the file.

8

Probably due to the current security in Android 11 - this option is not available. If something changes, I will let you know or be ahead of my update :slight_smile:

9

Hey! Did you find a solution?

10

Newer versions of Android have introduced additional security measures for file access. This is not Unity’s fault. And unfortunately, I haven’t found any other solution than keeping access to the file in the cloud or the value in a database - on the network, anyway.

1 Like
11

Shame :frowning: I suppose the cloud option would be the most reliable anyways. Even if there was a method for sharing files locally on a device (I’m currently reading about Android’s ContentProvider, not sure ), who’s to say they won’t deprecate that in a future release, making your apps not work for your clients over night.