title: how to open pdf, ppt, word, etc files in android?
body: <p>I am downloading certain types of files in my app (pdf, ppt, doc, mp4, etc). Right now I am launching these files in their default applications in the device.
  Is there any way that I might open these inside my own app?</p>
  
  <p>I have explored other similar questions, I am currently trying out apache poi api for my purpose but I am not sure it will work on all types of files.</p>
  
  <p>I want to know if I have to decode and render these formats in my own applications, what kind of an effort will that take?
  And also, since I don't know where to start, is there reference available from which I could get help?</p>
  
  <p>Thanks in advance.</p>