How can I show a progress bar when I click a button during the creation of a PDF file and hide it when I finished creating the file?

```
  public class TwoFragment extends android.support.v4.app.Fragment {

    private View v;
    Intent chooser=null;
    String myInt="";
    String ciao="";
    private String string="";
    private ProgressBar pdfProgress;
    ProgressTask task;

    public TwoFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        View rootView = inflater.inflate(R.layout.fragment_two, container, false);

        Button mButton = (Button) rootView.findViewById(R.id.newbutton);
        mButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {

                //sendemail();
               // pdfProgress.setVisibility(View.GONE);

               /* pdfProgress.setVisibility(View.VISIBLE);
                createPDF();
                pdfProgress.setVisibility(View.GONE);
                viewPDF();*/
                /*MyAsyncTask myTask = new MyAsyncTask();
                myTask.execute();
*/
                showProgress();

            }
        });
        TextView titolo3 = (TextView)rootView.findViewById(R.id.result);
        TextView titolo2 = (TextView)rootView.findViewById(R.id.result2);
        TextView titolo4 = (TextView)rootView.findViewById(R.id.resultpizze);
        pdfProgress = (ProgressBar)rootView.findViewById(R.id.progressbar);
        pdfProgress.setVisibility(View.GONE);

        //pdfProgress.setVisibility(View.INVISIBLE);

        //TextView titolo = (TextView)rootView.findViewById(R.id.quantità3);
     /*  class MyAsyncTask extends AsyncTask<Void, Void, Void> {
            @Override
            protected Void doInBackground(Void... params) {
                // This runs in new thread!!!
                // Always run long operations in another thread, so GUI will never be blocked
                createPDF();

                return null;
            }

            @Override
            protected void onPostExecute(Void v) {
                // This runs in MAIN thread, after the job's done.
                // You always have to update gui from main thread
                pdfProgress.setVisibility(View.GONE);
                viewPDF();
            }
        }
*/
  Bundle bundle2=getArguments();
        if(bundle2 != null){
             string = bundle2.getString("scelta2");
            titolo3.setText(string);

        }

    /*    Bundle bundle2=getArguments();
        if(bundle2 != null){
           //  myInt = bundle2.getString("scelta2",myInt);
            cacca=bundle2.getString("result",null);

            //cacca=myInt;
           // Log.d("ciao",cacca);
           titolo3.setText(cacca);
        }*/

        //titolo3.setText(myInt);

    /*    Bundle bundle3=getArguments();
        if(bundle3 != null){
           // String myInt3 = bundle3.getString("totalebirre", null);
           //  cazzo2=Integer.parseInt(myInt3);
           int cazzo2=bundle3.getInt("totalebirre");
            titolo2.setText(String.valueOf(cazzo2));

        }
        Bundle bundle=getArguments();
        if(bundle != null){
            // String myInt2 = bundle2.getString("totalepizze", null);
            //   cazzo=Integer.parseInt(myInt2);
            //titolo2.setText(myInt2);
            String string=bundle.getString("scelta3", null);
             titolo4.setText(string);

        }
*/

        return rootView;
    }

/* public void sendemail(){

        Intent intent = new Intent(Intent.ACTION_SEND);
        intent.setData(Uri.parse("mailto:"));
        String[] to={"marco_marcoletto@hotmail.it"};
        intent.putExtra(Intent.EXTRA_EMAIL,to);
        intent.putExtra(Intent.EXTRA_SUBJECT, "ciao");
        intent.putExtra(Intent.EXTRA_TEXT, "zao");
        intent.setType("message/rfc822");
        chooser=intent.createChooser(intent,"manda email");
        startActivity(chooser);
    }*/

   //@TargetApi(Build.VERSION_CODES.M)
    public void createPDF() {

       Document doc = new Document();

       try {
           String path = Environment.getExternalStorageDirectory()
                   .getAbsolutePath() + "/droidText";

           File dir = new File(path);
           if (!dir.exists())
               dir.mkdirs();

           Log.d("PDFCreator", "PDF Path: " + path);

           //File file = new File(dir, "sample.pdf");
           File file = new File(dir, "salve.pdf");

           FileOutputStream fOut = new FileOutputStream(file);

           PdfWriter.getInstance(doc, fOut);

           // open the document
           doc.open();
           ByteArrayOutputStream stream = new ByteArrayOutputStream();
           Bitmap bitmap = BitmapFactory.decodeResource(getContext()
                   .getResources(), R.drawable.androtuto);
           bitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
           Image myImg = Image.getInstance(stream.toByteArray());
           myImg.setAlignment(Image.MIDDLE);

           // add image to document
           doc.add(myImg);
           Paragraph p1 = new Paragraph(string);
           Font paraFont = new Font(Font.COURIER);
           p1.setAlignment(Paragraph.ALIGN_CENTER);
           p1.setFont(paraFont);

           // add paragraph to document
           doc.add(p1);

           Paragraph p2 = new Paragraph("Bonjour Android Tuto");

           Font paraFont2 = new Font(Font.COURIER, 14.0f, Color.GREEN);
           p2.setAlignment(Paragraph.ALIGN_CENTER);
           p2.setFont(paraFont2);

           doc.add(p2);

           stream = new ByteArrayOutputStream();
           bitmap = BitmapFactory.decodeResource(getContext()
                   .getResources(), R.drawable.android);
           bitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
           myImg = Image.getInstance(stream.toByteArray());
           myImg.setAlignment(Image.MIDDLE);

           // add image to document
           doc.add(myImg);

           // set footer
           Phrase footerText = new Phrase("Pied de page ");
           HeaderFooter pdfFooter = new HeaderFooter(footerText, false);
           doc.setFooter(pdfFooter);

       } catch (DocumentException de) {
          // Log.e("PDFCreator", "DocumentException:" + de);
           Log.e("PDFCreator", "DocumentException:" + de.getMessage());
       } catch (IOException e) {
         //  Log.e("PDFCreator", "ioException:" + e);
           Log.e("PDFCreator", "DocumentException:" + e.getMessage());

       } finally {
           doc.close();
       }

   }
    public void viewPDF(){
        String path = "/sdcard/droidText/salve.pdf";

        File targetFile = new File(path);
        Uri targetUri = Uri.fromFile(targetFile);

        Intent intent;
        intent = new Intent(Intent.ACTION_VIEW);
        intent.setDataAndType(targetUri, "application/pdf");

        startActivity(intent);
    }
    private class ProgressTask extends AsyncTask<Integer,Integer,Void> {

        protected void onPreExecute() {
            pdfProgress.setMax(100); // set maximum progress to 100.
        }

        protected void onCancelled() {
            pdfProgress.setMax(0); // stop the progress
        }
        protected Void doInBackground(Integer... params) {
            int start=params[0];
            for(int i=start;i<=100;i+=5){
                try {
                    boolean cancelled=isCancelled();
                    if(!cancelled) {
                        publishProgress(i);
                        Log.v("Progress","increment " + i);
                        //onProgressUpdate(i);
                        SystemClock.sleep(1000);
                    }
                    createPDF();
                } catch (Exception e) {
                    Log.e("Error", e.toString());
                }
            }
            return null;
        }
        protected void onProgressUpdate(Integer... values) {

            // increment progress bar by progress value
            //setProgress(10);
        }
        protected void onPostExecute(Void result) {
            // async task finished
            Log.v("Progress", "Finished");
            viewPDF();
        }

    }
    public void showProgress() {
        task = new ProgressTask();
        // start progress bar with initial progress 10
        ///////////////////task.execute(10,10,null);
        task.execute(10);

    }
}

```