title: Android Storage Access Framework - start picker for custom file type
body: <p>I am trying to use the SAF picker in my application to look for my custom file types. Doing this is easy enough when the file has a mime type by calling setType("text/plain") or similar.</p>
  
  <p>What would the call look like if I wanted to look for, say, all files with the '.blah' extension?</p>
  
  <p><strong>Edit</strong>: more information: the file type is actually a plain text file with a changed extension. In the file, some text exists which I parse to create some data structure from it. However, when the user looks for the file of the specific extension, I would like them to see only my custom files, not all text files.</p>