Android Fragments: Text updating within Thread after switching the fragment

Question

I'am trying to build a little voice recording app with 3 Tabs as Fragments. I learned that 2 Tabs will be created with onCreateView when i start the app. At first i expected that onCreatView in PlaceHolderFragment will be called for the new Fragment to be displayed each time switching the Fragment. (It's the simple Fragment Acitivty Demo in Android Studio which i extended for voice recording).

        @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View rootView;

        Integer section = getArguments().getInt(ARG_SECTION_NUMBER);

        switch (section) {
            case 1:

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

                TextView textView = (TextView) rootView.findViewById(R.id.section_label);
                textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));

                final TextView timeView;
                timeView = (TextView) rootView.findViewById(R.id.timeView);

                //Button start_stop;
                final Button start_stop = (Button) rootView.findViewById(R.id.button);

                start_stop.setOnClickListener(new View.OnClickListener() {
                    public void onClick(View v) {

                        MainActivity mainAct = (MainActivity) getActivity();

                        if (recorder == null) {
                            recorder = new MediaRecorder();
                        }

                        if (mainAct.running) {

                            recorder.stop();
                            start_stop.setText("start recording");

                            mainAct.running = false;
                            mainAct.time = 0;

                        } else {

                            recorder.setAudioSource(MediaRecorder.AudioSource.MIC);
                            recorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
                            //recorder.setOutputFile(Environment.getExternalStorageDirectory().getAbsolutePath() + "/myrecording.mp3");
                            recorder.setOutputFile(getActivity().getApplicationContext().getFilesDir() + "/audio.mp3");
                            recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
                            try {
                                recorder.prepare();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }

                            recorder.start();
                            mainAct.running = true;
                            mainAct.initThread(timeView);

                            start_stop.setText("stop recording");
                        }

                    }
                });

                break;

            case 2:

                rootView = inflater.inflate(R.layout.fragment_sound, container, false);
                break;

            case 3:

                rootView = inflater.inflate(R.layout.fragment_pics, container, false);
                break;

            default:
                rootView = null;
                break;
        }

        return rootView;
    }`

The recorded duration will be displayed within a TextView. The time is updated within a new Thread.

    public void initThread(final TextView timeView) {
    refreshThread = new Thread(new Runnable() {
        public void run() {
            while (running) {
                time = time + 0.1;
                try {
                    Thread.sleep(100);
                } catch (InterruptedException ex) {
                    Logger.getLogger(MainActivity.class.getName()).log(Level.SEVERE, null, ex);
                }
                runOnUiThread(new Runnable() {
                    public void run() {
                        timeView.setText(getString(R.string.time_string, String.format("%.1f", time)));
                    }
                });

            }
        }
    });
    refreshThread.start();
}

so far everything works fine - recording is running when I'm on the first tab (which displays the duration) - even when i switch to the second tab. But when i switch to the third tab and go back to the first tab the duration isn't displayed any longer.

exact: When i got from Tab 1 to Tab 2 and back to Tab 1 time is still updating as expected. Going from Tab 1 to Tab 2 to Tab 3 and back to Tab 2 and to Tab 1 everything seems to be initial on this screen. Time won't be updated anye longer - the TextView has the inital text. I debugged the app, when going back from Tab 3 the Threat is still running, but the TextView won't get the current duration.

Can somebody please give me a hint for this behavior? I think when going to Tab 3 the fragment for Tab 1 will be destroyed - but it will be built again when switching to Tab 1.

How to solve this issue?

Thx