另一个简单的解决方案:

    public class MyPagerAdapter extends FragmentPagerAdapter {
        private Fragment mCurrentFragment;

        public Fragment getCurrentFragment() {
            return mCurrentFragment;
        }
//...    
        @Override
        public void setPrimaryItem(ViewGroup container, int position, Object object) {
            if (getCurrentFragment() != object) {
                mCurrentFragment = ((Fragment) object);
            }
            super.setPrimaryItem(container, position, object);
        }
    }

在/values/integers.xml中创建整数资源id

<integer name="page1">1</integer>
<integer name="page2">2</integer>
<integer name="page3">3</integer>

然后在PagerAdapter中使用getItem函数:

public Fragment getItem(int position) {

        Fragment fragment = null;

        if (position == 0) {
            fragment = FragmentOne.newInstance();
            mViewPager.setTag(R.integer.page1,fragment);

        }
        else if (position == 1) {

            fragment = FragmentTwo.newInstance();
            mViewPager.setTag(R.integer.page2,fragment);

        } else if (position == 2) {

            fragment = FragmentThree.newInstance();
            mViewPager.setTag(R.integer.page3,fragment);

        }

        return fragment;
        }

然后在activity中写这个函数来获取片段引用:

private Fragment getFragmentByPosition(int position) {
    Fragment fragment = null;

    switch (position) {
        case 0:
            fragment = (Fragment) mViewPager.getTag(R.integer.page1);
            break;

        case 1:

            fragment = (Fragment) mViewPager.getTag(R.integer.page2);
            break;

        case 2:
            fragment = (Fragment) mViewPager.getTag(R.integer.page3);
            break;
            }

            return fragment;
    }

通过调用上面的函数来获取片段引用，然后将其转换为自定义片段:

Fragment fragment = getFragmentByPosition(position);

        if (fragment != null) {
                    FragmentOne fragmentOne = (FragmentOne) fragment;
                    }

你不需要在后面的阶段调用getItem()或其他方法来获取托管在ViewPager内部的Fragment的引用。如果你想在Fragment中更新一些数据，那么使用这种方法:动态更新ViewPager ?

关键是在Adaper中设置新数据并调用notifyDataSetChanged()，后者将调用getItemPosition()，传递给你Fragment的引用并让你有机会更新它。所有其他方法都需要你参考自己或其他方法，这不是一个好的解决方案。

@Override
public int getItemPosition(Object object) {
    if (object instanceof UpdateableFragment) {
        ((UpdateableFragment) object).update(xyzData);
    }
    //don't return POSITION_NONE, avoid fragment recreation. 
    return super.getItemPosition(object);
}

这是基于上面Steven的回答。这将返回已经附加到父活动的片段的实际实例。

FragmentPagerAdapter fragmentPagerAdapter = (FragmentPagerAdapter) mViewPager.getAdapter();
    for(int i = 0; i < fragmentPagerAdapter.getCount(); i++) {

        Fragment viewPagerFragment = (Fragment) mViewPager.getAdapter().instantiateItem(mViewPager, i);
        if(viewPagerFragment != null && viewPagerFragment.isAdded()) {

            if (viewPagerFragment instanceof FragmentOne){
                FragmentOne oneFragment = (FragmentOne) viewPagerFragment;
                if (oneFragment != null){
                    oneFragment.update(); // your custom method
                }
            } else if (viewPagerFragment instanceof FragmentTwo){
                FragmentTwo twoFragment = (FragmentTwo) viewPagerFragment;

                if (twoFragment != null){
                    twoFragment.update(); // your custom method
                }
            }
        }
    }

为了从ViewPager中获取当前可见片段。我用了这个简单的语句，效果很好。

      public Fragment getFragmentFromViewpager()  
      {
         return ((Fragment) (mAdapter.instantiateItem(mViewPager, mViewPager.getCurrentItem())));
      }

好的适配器FragmentStatePagerAdapter我基金一个解决方案:

在你的FragmentActivity:

ActionBar mActionBar = getSupportActionBar(); 
mActionBar.addTab(mActionBar.newTab().setText("TAB1").setTabListener(this).setTag(Fragment.instantiate(this, MyFragment1.class.getName())));
mActionBar.addTab(mActionBar.newTab().setText("TAB2").setTabListener(this).setTag(Fragment.instantiate(this, MyFragment2.class.getName())));
mActionBar.addTab(mActionBar.newTab().setText("TAB3").setTabListener(this).setTag(Fragment.instantiate(this, MyFragment3.class.getName())));

viewPager = (STViewPager) super.findViewById(R.id.viewpager);
mPagerAdapter = new MyPagerAdapter(getSupportFragmentManager(), mActionBar);
viewPager.setAdapter(this.mPagerAdapter);

在你的类FragmentActivity中创建一个方法——这样你就可以访问你的Fragment，你只需要给它你想要的Fragment的位置:

public Fragment getActiveFragment(int position) {
String name = MyPagerAdapter.makeFragmentName(position);
return getSupportFragmentManager().findFragmentByTag(name);
}

在适配器中:

public class MyPagerAdapter extends FragmentStatePagerAdapter {

private final ActionBar actionBar;
private final FragmentManager fragmentManager;

public MyPagerAdapter(FragmentManager fragmentManager, com.actionbarsherlock.app.ActionBarActionBar mActionBar) {super(fragmentManager);
this.actionBar = mActionBar;
this.fragmentManager = fragmentManager;
}

@Override
public Fragment getItem(int position) {
getSupportFragmentManager().beginTransaction().add(mTchatDetailsFragment, makeFragmentName(position)).commit();
return (Fragment)this.actionBar.getTabAt(position);
}

@Override
public int getCount() {
return this.actionBar.getTabCount();
}

@Override
public CharSequence getPageTitle(int position) {
return this.actionBar.getTabAt(position).getText();
}

private static String makeFragmentName(int viewId, int index) {
return "android:fragment:" + index;
}

}