Share file to another app (whatsapp, telegram, gmail)

Question

I'm developing an android app using Xamarin.Forms.

So far i did not found too much difficulties during the development, but now i think i'm missing something.

I would like to:

1. share a custom file (*.sl) from my app to any app that can handle Attachments (like whatsapp, telegram, gmail.. etc)
2. Open my custom file (*.sl) with my app

So, i digged a bit around the web and ended up with this;

In my AndroidManifest.xml to handle my custom file

   <intent-filter>
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.BROWSABLE" />
    <category android:name="android.intent.category.DEFAULT" />
    <data android:scheme="file" />
    <data android:host="*" />
    <data android:mimeType="*/*" />
    <data android:pathPattern=".*\.sl" />
  </intent-filter>
  <intent-filter>
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.BROWSABLE" />
    <category android:name="android.intent.category.DEFAULT" />
    <data android:scheme="content" />
    <data android:mimeType="application/octet-stream" />
    <data android:mimeType="application/sl" />
  </intent-filter>

And this class, used as a Service from my Xamarin.Forms pcl

public class ShareDroid : IShare
{
    private Context _context;
    private FileSystemExDroid _fsDroid;

    public ShareDroid()
    {
        _context = Android.App.Application.Context;
        _fsDroid = new FileSystemExDroid();
    }

    public void Show(string title, string message, string filePath)
    {
         if(!_fsDroid.FileExists(filePath))
            return;

        var extension = filePath.Substring(filePath.LastIndexOf(".", StringComparison.Ordinal) + 1).ToLower();
        var contentType = GetContentType(extension);

        var intent = new Intent(Intent.ActionSend);
        intent.SetType(contentType);
        intent.PutExtra(Intent.ExtraStream, Uri.Parse("file://" + filePath));
        intent.PutExtra(Intent.ExtraText, string.Empty);
        intent.PutExtra(Intent.ExtraSubject, message ?? string.Empty);

        var chooserIntent = Intent.CreateChooser(intent, title ?? string.Empty);
        chooserIntent.SetFlags(ActivityFlags.ClearTop);
        chooserIntent.SetFlags(ActivityFlags.NewTask);
        _context.StartActivity(chooserIntent);
    }

    private static string GetContentType(string extension)
    {
        string contentType;

        switch (extension)
        {
            case "pdf":
                contentType = "application/pdf";
                break;
            case "png":
                contentType = "image/png";
                break;
            case "sl":
                contentType = "application/sl";
                break;
            default:
                contentType = "application/octet-stream";
                break;
        }

        return contentType;
    }
}

And here i call the Show method of my share service

private void OnShare()
{
    var fileSystem = DependencyService.Get<IFileSystemEx>();
    var serializer = DependencyService.Get<ISerializer>();
    var share = DependencyService.Get<IShare>();
    var fileName = $"{Name}_{Id}.sl";
    var path = fileSystem.CreateFilePath(fileName, SpecialFolder.Personal);
    serializer.Save(path, Model);
    share.Show(Resources.ShareViaLabel, Resources.ShareViaMessage, path);
}

When i test the app on any device (not emulated) i get the same result.

• Gmail says "Permission denied for the attachment"
• WhatsApp and Telegram says "Attachment not supported"

The Resources.ShareViaMessage (which is a little description) gets printed in the target app without problem.

The custom file is actually a .txt file with a custom extension (.sl).

Anyone can help?

Answer 1

In the end i came up with a solution. I removed the intents from the manifest, and coded them in the main activity like this:

[IntentFilter(
new[] { Intent.ActionView }, 
Categories = new [] { Intent.CategoryBrowsable, Intent.CategoryDefault }, 
DataMimeType = "text/plain",
DataPathPatterns = new []
{
    @".*\\.sl",
    @".*\\..*\\.sl",
    @".*\\..*\\..*\\.sl",
    @".*\\..*\\..*\\..*\\.sl"
})]
[IntentFilter(
new[] { Intent.ActionSend },
Categories = new[] { Intent.CategoryBrowsable, Intent.CategoryDefault },
DataMimeType = "text/plain",
DataPathPatterns = new []
{
    @".*\\.sl",
    @".*\\..*\\.sl",
    @".*\\..*\\..*\\.sl",
    @".*\\..*\\..*\\..*\\.sl"
})]

also changed the Share.Show method to use the uri from the fileprovider:

public void Show(string title, string filePath)
    {
        if(!_fsDroid.FileExists(filePath))
            return;

        var fileUri = FileProvider.GetUriForFile(_context, "com.***********.******.fileprovider", new File(filePath));
        var intent = new Intent(Intent.ActionSend);
        intent.SetType("text/plain");
        intent.PutExtra(Intent.ExtraText, string.Empty);
        intent.PutExtra(Intent.ExtraStream, fileUri);
        intent.SetData(fileUri);
        intent.SetFlags(ActivityFlags.GrantReadUriPermission);
        intent.SetFlags(ActivityFlags.ClearTop);
        intent.SetFlags(ActivityFlags.NewTask);

        var chooserIntent = Intent.CreateChooser(intent, title ?? string.Empty);
        _context.StartActivity(chooserIntent);
    }

In the manifest, inside the application tag i added

  <provider android:name="android.support.v4.content.FileProvider" android:authorities="com.***********.******.fileprovider" android:exported="false" android:grantUriPermissions="true">
    <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/file_paths" />
  </provider>

and this is the content of my file_paths.xml

<paths xmlns:android="http://schemas.android.com/apk/res/android">
  <files-path name="exports" path="exports/"/>
</paths>

And now my application exports .sl file, and whatsapp, telegram, gmail and any other app that support text/plain file accepts the attachments.

Also, when opening/sending the .sl file my app is listed and usable as default for this kind of file.

Hope this helps out someone else in the future :)