Question

I’d like to call a method that is declared in a class, but the class that contains that method is instantiated by a fragment:

 protected void setupViewPager() {

    List<Fragment> fragments = new Vector<Fragment>();

    fragments.add(Fragment.instantiate(this, AFTab1.class.getName()));
    fragments.add(Fragment.instantiate(this, AFTab2.class.getName()));
    fragments.add(Fragment.instantiate(this, AFTab3.class.getName()));

    this.mPagerAdapter  = new PagerAdapter(super.getSupportFragmentManager(), fragments);
    this.mViewPager = (ViewPager)super.findViewById(R.id.viewpager);
    this.mViewPager.setAdapter(this.mPagerAdapter);
    this.mViewPager.setOnPageChangeListener(this);
}

So for example, if I want to call AFTab1’s method, how can I go about doing that?

Answer 1

There are several options for you. You can store a reference to the fragment returned by instantiate(), you can give the fragment an id, and you can give it a tag (and I bet there are more options). In your case I would store a reference like this:

protected void setupViewPager() {

    List<Fragment> fragments = new Vector<Fragment>();

    AFTab1 tab1 = (AFTab1) Fragment.instantiate(this, AFTab1.class.getName());
    AFTab2 tab2 = (AFTab2) Fragment.instantiate(this, AFTab2.class.getName());
    AFTab3 tab3 = (AFTab3) Fragment.instantiate(this, AFTab3.class.getName());

    fragments.add(tab1);
    fragments.add(tab2);
    fragments.add(tab3);

    tab1.aMethod();

    ...

You can of course store the reference for later use but beware of leakage.

Update: Note that you can create a fragment in many ways as well, for example using its constructor. You don’t have to use instantiate().