获取ViewPager当前展示的Fragment

转自：http://tamsler.blogspot.com/2011/11/android-viewpager-and-fragments-part-ii.html

What are the different ways to get a reference to the currently visible fragment page in a ViewPager?

First Solution

You can set a unique tag on each fragment page:

getSupportFragmentManager().beginTransaction().add(myFragment, "Some Tag").commit();

... and then retrieve the fragment page via:

getSupportFragmentManager().findFragmentByTag("Some Tag");

Using this approach, you need to keep track of the string tags and associate them with all the fragment pages. You could use a map to store each tag along with the current page index, which is set at the time when
the fragment page is instantiated.

MyFragment myFragment = MyFragment.newInstance();

mPageReferenceMap.put(index, "Some Tag");
getSupportFragmentManager().beginTransaction().add(myFragment, "Some Tag").commit();

To get the tag for the currently visible page, you then call:

int index = mViewPager.getCurrentItem();

String tag = mPageReferenceMap.get(index);

... and then get the fragment page:

Fragment myFragment = getSupportFragmentManager().findFragmentByTag(tag);

Second Solution

Similar to the first solution, you keep track of all the "active" fragment pages. In this case, you keep track of the fragment pages in the FragmentStatePagerAdapter, which is used by the ViewPager.

public Fragment getItem(int index) {

Fragment myFragment = MyFragment.newInstance();

mPageReferenceMap.put(index, myFragment);

return myFragment;

}

To avoid keeping a reference to "inactive" fragment pages, we need to implement the FragmentStatePagerAdapter's destroyItem(...) method:

public void destroyItem(View container, int position, Object object)
{

super.destroyItem(container, position, object);

mPageReferenceMap.remove(position);
}

... and when you need to access the currently visible page, you then call:

int index = mViewPager.getCurrentItem();

MyAdapter adapter = ((MyAdapter)mViewPager.getAdapter());
MyFragment fragment = adapter.getFragment(index);

... where the MyAdapter's getFragment(int) method looks like this:

public MyFragment getFragment(int key) {

return mPageReferenceMap.get(key);
}

I am using the second solution in my project,
and it's working quite well. Here is the reference to the fullsource
code.