Detect that the user is swiping away from the fragment in a viewpager

Question

I have a survey app which is implemented using a viewpager and an arraylist of fragments. The fragments have different view types, some have radio buttons, some input boxes. I want the save the entered data to a shared variable in the parent activity when the user navigates from one fragment to another. When the user reaches the last fragment i want to display the summary of the data. i was thinking of saving the data when the user navigates from one fragment to the next. Also not sure if it is the best way to go about it.

    List<Question> questions = new SurveyServiceImpl(getApplicationContext()).getSurveyQuestions(1);
    ArrayList<Fragment> questionFragments = new ArrayList<>();
    questionFragments.add(HomeFragment.newInstance("", ""));
    for (int i = 0; i < questions.size(); i++) {
        switch (questions.get(i).getQuestionType()) {
            case SELECT:
                if (questions.get(i).getMaximumOptionsRequired() == 1)
                    questionFragments.add(QuestionTypeSelect.newInstance("", questions.get(i)));
                else
                    questionFragments.add(QuestionTypeCheckBox.newInstance("", questions.get(i)));
                break;
            case INPUT:
                questionFragments.add(QuestionTypeInput.newInstance("", questions.get(i)));
                break;
            default:
        }
    }
    questionFragments.add(EndFragment.newInstance("", ""));
    final ViewPager pager = (ViewPager) findViewById(R.id.viewPager);
    pager.setAdapter(new MyPagerAdapter(getSupportFragmentManager(), questionFragments));

score 1 · Answer 1 · answered Sep 29 '17 at 17:43

Use OnPageChangeListener for: all scrolls; page centered; page scroll changes (start drag, finish center animation)

pager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { }
        @Override public void onPageSelected(int position) { }
        @Override
        public void onPageScrollStateChanged(int state) {
            if (state == ViewPager.SCROLL_STATE_DRAGGING) {
//User started moving current page
}});

score 0 · Answer 2 · answered Sep 29 '17 at 17:38

Off the top of my head: Save the data as soon as it is changed in each fragment :
For EditTexts, use TextWatcher : (example) to save the text when it changes in afterTextChanged().
For RadioButtons, use radioButton.setOnClickListener(/**Save data in onClick*/), or radioGroup.setOnCheckedChangeListener if you're using a RadioGroup (example).
Might not be the most efficient solution, but works :) .

score 0 · Answer 3 · answered Sep 29 '17 at 17:45

Hmm. Well unless you are doing some sort of save checkmarks along the wizard flow that you want to represent that all data for that page was saved, I would not go that route personally. You can easily just recognize pageChanged listener

      vpMain.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            //Generated method stub
        }

        @Override
        public void onPageSelected(int position) {
            setCurrentPage(position);
            PAGE_TO_RETURN_TO = position;
            vpMain.setCurrentItem(PAGE_TO_RETURN_TO);
            validate data and allow to scroll or save
        }

        @Override
        public void onPageScrollStateChanged(int state) {
            //Generated Method Stub
        }
    });

but I would prefer to see onPause() of the parent activity handle saving the data personally. But it really depends on your need for the app.

Detect that the user is swiping away from the fragment in a viewpager

3 Answers3