Android startCamera gives me null Intent and ... does it destroy my global variable?

I have the next problem:

when I try to start my camera, I can take the picture, even save it on my sdcard, but when I'm going to get the path for showing it on my device I get errors.

My global variables are 2 (I used 1 but 2 are better for making sure it's a strange error):

    private File photofile;
private Uri mMakePhotoUri;

and this is my start-camera function:

@SuppressLint("SimpleDateFormat")
public void farefoto(int num){
// For naming the picture
    SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd_HHmmss");
    String n = sdf.format(new Date());
    String fotoname = "Immagine-"+ n +".jpg";

//Going through files and  folders
    File photostorage = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
    File photostorage2 = new File(photostorage, "Immagini");
    System.out.println(photostorage+"\n"+photostorage2);
    photostorage2.mkdirs();
// My file (global)
    photofile = new File(photostorage2, fotoname);
    Intent i = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); //intent to start camera
// My URI (global)
    mMakePhotoUri = Uri.fromFile(photofile);
    new Bundle(); // I took this code from internet, but if I remove this line, it's the same
    i.putExtra(MediaStore.EXTRA_OUTPUT, mMakePhotoUri);
    startActivityForResult(i, num); //num would be 1 on calling function
}

and my activityresult:

   @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        // TODO Auto-generated method stub
        if (requestCode == 1){

            try{ // tring my global URI
                photo = f.decodeAndResizeFile(new File(mMakePhotoUri.getPath()));
            }
            catch(NullPointerException ex){
                System.out.println("fail");
                ex.printStackTrace();
                try{ // Trying my global FILE
                photo = BitmapFactory.decodeFile(photofile.getAbsolutePath());
                } catch (Exception e){
                    e.printStackTrace();
                    Toast.makeText(this, "C'è stato un errore. Riprova a scattare la foto.", Toast.LENGTH_LONG).show();
                }

......
......
.......
}

Always getting NullPointerException

But... if I take the picture again, IT WORKS!!.

I've read everything I could here... but it doesn't have logic when I modify a global variable and I cannot take it again...

Thanks in advance. Cheers.

SOLUTION

As Alex Cohn said, my problem was that I was calling onCreate before onActivityResult because of a probably push out of memory (because sometimes doesn't do it), so I wanted to have my app "healthy" and I tried some try / catch and so I get the data even if it's calling onCreate or onActivityResult for the first call, and I wrote that data in a Bundle like explained in the link of restoring our state.

Thanks!.