Call function in fragment from MainActivity

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fragment A with function A1
fragment B with function B1
Two tabs in main activity
tabA got fragment A
tabB got fragment B
my problem is : call function A1 from main activity

 //here i create taps and fragment into viewpaper

 private void setupViewPager(ViewPager viewPager){
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new OneFragment(),"ONE");
    adapter.addFragment(new TwoFragment(),"TWO");
    viewPager.setAdapter(adapter);
}



 class ViewPagerAdapter extends FragmentPagerAdapter{
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();
        @Nullable
        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }

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

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

@Override
public int getCount() {
    return mFragmentList.size();
}
public void addFragment(Fragment fragment,String tittle){
    mFragmentList.add(fragment);
    mFragmentTitleList.add(tittle);
}
 }

Answer 1

Based on the code you posted, you could just save an instance of the fragment directly in your Activity like this

private OneFragment f1;
private TwoFragment f2;

private void setupViewPager(ViewPager viewPager){
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    f1 = new OneFragment();
    f2 = new TwoFragment();
    adapter.addFragment(f1,"ONE");
    adapter.addFragment(f2,"TWO");
    viewPager.setAdapter(adapter);
}

then anywhere in your activity you want to use them just call

f1.myMethod();
f2.myMethod();

You could also just save your adapter and use it to access the Fragments, as in

private ViewPagerAdapter adapter;

private void setupViewPager(ViewPager viewPager){
    adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new OneFragment(),"ONE");
    adapter.addFragment(new TwoFragment(),"TWO");
    viewPager.setAdapter(adapter);
}

and to access them in the Activity call

OneFragment f1 = (OneFragment)adapter.getItem(0);
TwoFragment f2 = (TwoFragment)adapter.getItem(1);