Android: How to open a specific folder via Intent and show its content in a file browser?

This should work:

Uri selectedUri = Uri.parse(Environment.getExternalStorageDirectory() + "/myFolder/");
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(selectedUri, "resource/folder");

if (intent.resolveActivityInfo(getPackageManager(), 0) != null)
{
    startActivity(intent);
}
else
{
    // if you reach this place, it means there is no any file 
    // explorer app installed on your device
}

Please, be sure that you have any file explorer app installed on your device.

EDIT: added a shantanu's recommendation from the comment.

LIBRARIES: You can also have a look at the following libraries https://android-arsenal.com/tag/35 if the current solution doesn't help you.

I finally got it working. This way only a few apps are shown by the chooser (Google Drive, Dropbox, Root Explorer, and Solid Explorer). It's working fine with the two explorers but not with Google Drive and Dropbox (I guess because they cannot access the external storage). The other MIME type like "*/*" is also possible.

public void openFolder(){
    Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
    Uri uri = Uri.parse(Environment.getExternalStorageDirectory().getPath()
         +  File.separator + "myFolder" + File.separator);
    intent.setDataAndType(uri, "text/csv");
    startActivity(Intent.createChooser(intent, "Open folder"));
}