Fragment+ page adapter

///interface 

public interface FragmentViewInterface {
    void onViewCreated(View layout);
    void onResumeFragment();
    void onPauseFragment();
}

///in fragment
  public void onActivityCreated (Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        try {
            FragmentViewInterface callback = (FragmentViewInterface) getActivity();
            callback.onViewCreated(root);
        } catch (ClassCastException e) {
            Log.e("ERROR", getActivity().getCallingPackage()+" must implement FragmentViewInterface");
        }
    }
      @Override
    public void onViewCreated(View layout) {
        
    }
    
    @Override
    public void onResumeFragment() {
    
    }
    
    @Override
    public void onPauseFragment() {
        this.removeTextChangedListener();
        this.clearEditText();
        this.addTextChangeListener();
    }
    
///in main activity

private void init(){
        mPager = findViewById(R.id.containerForInputText);
        mPagerAdapter = new SlidePagerAdapter(getSupportFragmentManager());
        mPager.setAdapter(mPagerAdapter);
        mPager.setPagingEnabled(false);
        mPager.addOnPageChangeListener(pageChangeListener);
}

private class SlidePagerAdapter extends FragmentPagerAdapter {
        LeftUserFragment leftUserFragment = LeftUserFragment.newInstance();
        RightUserFragment rightUserFragment = RightUserFragment.newInstance();
                
        public SlidePagerAdapter(FragmentManager fm) {
            super(fm);
            leftUserFragment.leftUserFragmentPutData(listView, chatArrayAdapter);
            rightUserFragment.rightUserFragmentPutData(listView, chatArrayAdapter);
        }
                
        @Override
        public Fragment getItem(int position) {
            if (position == 0) {
                return leftUserFragment;
            } else {
                return rightUserFragment;
            }
        }
        
        @Override
        public int getCount() {
            return NUM_PAGES;
        }
    }
    private ViewPager.OnPageChangeListener pageChangeListener = new ViewPager.OnPageChangeListener() {
        
        int currentPosition = 0;
        
        @Override
        public void onPageSelected(int newPosition) {
            FragmentViewInterface fragmentToShow = (FragmentViewInterface)mPagerAdapter.getItem(newPosition);
            fragmentToShow.onResumeFragment();
    
            FragmentViewInterface fragmentToHide = (FragmentViewInterface)mPagerAdapter.getItem(currentPosition);
            fragmentToHide.onPauseFragment();
    
            currentPosition = newPosition;
        }
        
        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) { }
        
        public void onPageScrollStateChanged(int arg0) { }