How to open file with any exetension in Android?

Question

I have an app in which user can upload file with any exetention(.png,.mp3,.txt,.pdf

Answer 1

Pointing to the first part of your question:

try
{
  Intent intent = new Intent(Intent.ACTION_VIEW, uri);
  startActivity(intent);
}
catch (ActivityNotFoundException e)
{
  //tel the user to install viewer to perform this action
}

There's no need to specify the type. It will get it from the data URI.