CODEWITHSUNDEEP
c#android.netxamarin.formsmaui
Julian
Julian

Reputation: 8924

How to correctly access existing files in the app data folder created with a Xamarin.Forms app inside a migrated MAUI app?

I am currently migrating an existing Xamarin.Forms app to .NET MAUI. The existing app uses an SQLite database to store some data.

The database path was set up as follows in the Xamarin.Forms app:

public static string DatabasePath
{
    get
    {
        var basePath = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
        return Path.Combine(basePath, "mydb.db3");
    }
}

In Xamarin.Forms, the resulting path on Android is:

/data/user/0/my.app/files/.local/share/mydb.db3

However, when using the exact same code as above in MAUI, the resulting path on Android is:

/data/user/0/my.app/files/mydb.db3

This creates the problem that existing data cannot be accessed in MAUI, unless I modify the code as follows in the migrated code:

public static string DatabasePath
{
    get
    {
        var basePath = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);

#if ANDROID
        var localShare = ".local/share";

        if (!basePath.Contains(localShare))
        {
            basePath = Path.Combine(basePath, localShare);
        }
#endif

        return Path.Combine(basePath, "mydb.db3");
    }
}

Now, this would solve my issue, but I don't think this is the right way. Does anyone know how to correctly migrate paths that were obtained using Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData) in order to access the exact same path as before?

This is important, because I need to be able to access and reuse the existing local database that was created with the Xamarin.Forms version from within the migrated MAUI app.

Note: I am aware that there are file system helpers for Xamarin.Forms and MAUI, but that doesn't help with this issue, because they weren't used when the Xamarin.Forms app was created.

Upvotes: 1

Views: 1594

Answers (2)

user2153142
user2153142

Reputation: 804

You may want to consider working at a lower level to get a better understanding of the Android file system.

The following will always return the folder of your app containing your data.

// the main data folder only available to your app
Java.IO.File folder = ContextCompat.GetExternalFilesDirs(Application.Context, null)[0];

In the debugger, you’ll see the string as “/storage/emulated/0/Android/data/packagename/files”, where your package name is in the usual format “com.companyname.appname”

You may have a subfolder created when first run the app where you keep specific data.

So, then you can get to the data via

string appDataFolder = System.IO.Path.Combine(folder.Path, GetString(Resource.String.your_app_data_folder));

I may want to debug the content of a user’s data file. The user sends me the file I can then access the data from the Assets folder of the project on my device, so I can then if necessary debug the problem on my device with the user’s data.

string filename = System.IO.Path.Combine(appDataFolder, diagnosticFileName);
using Stream asset = Assets!.Open(diagnosticFileName);

if (!File.Exists(filename))
{
    using FileStream fileStream = File.Create(filename);
    asset.CopyTo(fileStream);
}

Upvotes: 0

Leon Lu
Leon Lu

Reputation: 9244

I reproduced your problem. Exactly, after upgrading Xamarin to Maui, the path of Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData) method is missing the .local/share part. It is recommended to post this issue to github.

In addition, I found that the path to LocalApplicationData was mentioned in File Storage and Access with Xamarin.Android, but no documentation related to Maui was found.

So, in Maui, you can use the following method to refactor the code file path:

Path.Combine(Environment.GetFolderPath(Environment.SpecialFoler.Personal),".local/share/mydb.db3");

Although this is not much different from your solution, it is the officially used refactor the code path method.

Upvotes: 0

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