Android：更新标签内容

Question

I am new to Android development. I have a ViewPager which holds TabLayout (that has fixed number of tabs). The ViewPager has SectionPagerAdapter (that has a fragment corresponding to tabs).

Now, I want to update tab content when user selects the tab and as it becomes visible (or when user wants to refresh the content).

But I am not sure which is correct way I can do this.

So far till now I found two solutions:

1) Add listener to TabLayout :

tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() 
{
    @Override
    public void onTabSelected(TabLayout.Tab tab) 
    {
        mViewPager.setCurrentItem(tab.getPosition());
        // Update tab containts here
    }

    @Override
    public void onTabUnselected(TabLayout.Tab tab) 
    {

    }

    @Override
    public void onTabReselected(TabLayout.Tab tab) 
    {

    }
});

2) Use ViewPager.OnPageChangeListener to get callbacks for when a page fragment (inside Tab) becomes visible:

viewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() 
{
    @Override
    public void onPageSelected(int position) 
    {
        // Update tab containts here
    } 
});

Can someone expert in this please advice me?

Answer 1

The way a viewpager adapter works (with tabs) is that once you add your fragments to the viewpager, then you basically need to add content to your fragments and let the adapter manage which fragment is visible when a given tab is selected.

So, by simply using : OnTabSelectedListener interface on your tabLayout, all you need to do is `setCurrentItem(tab.getPosition()); on your viewPager reference (from your layout).

You can have a method like this to add fragments to your viewPagerAdapter:

private void setupViewPager(ViewPager viewPager){
    //then create an instance of your ViewPagerAdapter class here
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());

    //then add fragments for each TAB here
    //by calling a method inside your Adapter like this
    adapter.addFrag(new FragmentOne(), "TITLE HERE");
    adapter.addFrag(new FragmentTwo(), "TITLE TWO");

    //Now set your adapter here
    viewPager.setAdapter(adapter);
}

Now in your fragments, you can show different content accordingly.

I hope this helps!