Q:

Returning to wrong activity when back pressed from URI launched PDF

Im hoping this is simple, but im fairly confused as to what is going on.   I am launching a PDF from an Imagebutton in an android activity using a piece of code I copied from elsewhere in my app.   
if (v==imagebutton20) {

                File file = new File("/sdcard/documents/20.pdf");
                  if (file.exists()) {
                        Uri path = Uri.fromFile(file);
                        Intent intent = new Intent(Intent. ACTION_VIEW);
                        intent.setDataAndType(path, "application/pdf");
                        intent.setFlags(Intent. FLAG_ACTIVITY_CLEAR_TOP);

                        try {
                            startActivity(intent);
                            overridePendingTransition(R.anim.zoom_enter, R.anim.zoom_exit);
                        } 
                        catch (ActivityNotFoundException e) {

                        }
                  }
            }   //end of   load

The pdf loads fine but when i press back the activity that launched the pdf isnt show, instead it returns to the activity before.   I have tried commenting out the 
     intent.setFlags(Intent. FLAG_ACTIVITY_CLEAR_TOP);

but the same effect.   What am i missing?   Sorry but i couldnt make sense of the official android guide, must be having a thick day! 

Even more confused as I have checked the manifest file, the .xml for the activity (Brain) and yet each time i load the pdf using the code above back takes me back to the wrong activity (main) in my app.   I am calling the Brain activity from Main via an imageview, but that works fine.   When i launch the PDF above from Brain the back button takes me to Main and not the launching activity Brain. 
I am using the code above elsewhere in 2 other activites in my app and the back key behaves exactly as you want / expect.   Thats why i started checking the mainfest file, but no idea what im missing.   
ANY help would be ace please! 
Thanks. 

A:

I cannot explain why the following worked, but in case anyone else has a similar issue I solved the problem by:

Creating a new Android activity in eclipse. 
Copying the code from the misbehaving activity. 
Pasting the code in the newly created activity. 

Simple and not really sure why it worked, but it did.