Android MVP with view pager

Question

I am trying to implement MVP in my android project. But I am getting difficulty when i implement MVP with viewPagerAdapter. To implement MVP, we used to create fragment/view and presenter instance in Activity class.Fragment/view and presenter both will communicate with each other using contract. In this way, we decoupled view with presenter and cover all business logic with Unit test. But in case when we have tablayout inside activity. We have initiated fragments inside fragmentPagerAdapter. I am not sure, how to provide tab-fragment/view reference to its corresponding presenter.If I initialize presenter inside fragmentPagerAdapter that would bleach SRP(Single responsibility principal). If we create presenter instance inside Fragment that would generate coupled code and then we don't need contact to establish communication between fragment and presenter. Please provide architectural solution, so that i can achieve same MVP with view pager along with adhering all clean code principal.

For reference, please find below my adapter code, where i am initializing fragments for tab:

  @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:
                return getConfigurationsTabFragment();
            case 1:
                return UpdateTabFragment.newInstance();
            case 2:
                return ServiceTabFragment.newInstance();
            default:
                return null;
        }
    }

score 2 · Accepted Answer · answered Feb 22 '18 at 08:46

private class MyAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();

        public MyAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }
        public void addFragement(Fragment fragment){
            mFragmentList.add(fragment);
        }
    }

use it in activity:

    MyAdapter adapter = new MyAdapter(getChildFragmentManager());
    Fragment fragment1 = EmptyFragment.newInstance("this is page 1");
    Fragment fragment2 = EmptyFragment.newInstance("this is page 2");
    presenter1.setxxx(fragment1);
    presenter2.setxxx(fragment2);
    adapter.addFragement(fragment1);
    adapter.addFragement(fragment2);
    viewPager.setAdapter(adapter);

score 0 · Answer 2 · answered Feb 16 '19 at 22:48

Inject the presenters to the view pagers adapter is not enough.

if the activity gets killed and recreated the fragments inside the view pager are restored but the presenters not.

U will have to attach the presenters again ( which is a little hacky ) by iterating on the fragments inside the fragment managers and attach them the presenters.

  Fragment fragment = getChildFragmentManager().findFragmentByTag("android:switcher:" 
  + mViewPager.getId() + ":" + {*position*});
    ((YourFragment)fragment).setPresenter(presenter)

Android MVP with view pager

2 Answers2