Null pointer Exception on file- URI?

Question

In my app a capture button is there to capture an image using device camera,so I have used a method captureImage() on the click event of that button.When I click the button

Answer 1

File mediaStorageDir = new File(
            Environment
                  .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
            Config.IMAGE_DIRECTORY_NAME);

I directly copied to code from Android getting started page. My problem was I was running it on emulator. Therefore I think the code above that I used could not assess my file system.