Android在View Pager的父活动中设置片段视图

Question

I have an activity which uses ViewPager and FragmentPagerAdapter to setup three fragments. Now when the activity loads, I issue a network request and plan to update the views in three fragments on reply from network. Now I am having difficulty to set those views from the main activity. Things I have tried (and spectacularly failed) are :

• Create a setter in Fragment Class to set the view data. In the fragment onViewCreated method I am saving global view references of textviews, and then try to call that setter from Activity on network load. The textviews are NULL, ie not even instantiated when setter is called.
• Create a getter in Activity to get the data from Fragments onViewCreated method.But in this case, the getter wont find the values as network request is not complete!

Any tips how to proceed? I have three fragments with related data and want to control their view settings from a single point. I dont want to make separate network calls from each Fragment.

Answer 1

• Create a setter in Fragment Class to set the view data. In the fragment onViewCreated method I am saving global view references of textviews, and then try to call that setter from Activity on network load. The textviews are NULL, ie not even instantiated when setter is called.

You're doing it right.

Why do those textviews have NULL value is all about a fragment reference you use when you call the setter method.

In short: add this function to your FragmentPagerAdapter implementation

public Fragment getFragmentByPositionUsingTag(int position) {
    Fragment fragment = fm.findFragmentByTag("android:switcher:" + R.id.viewPager + ":" + position);

    return fragment;
}

and try to use the reference it returns to call the method. (For more information there are many great answers on SO).