import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.view.ViewGroup;

import java.util.ArrayList;

public class adapter extends FragmentPagerAdapter
{
  private ArrayList<Fragment> fragmentList;
  public adapter(FragmentManager fm)
  {
    super(fm);
  }
  public adapter(FragmentManager fm, ArrayList<Fragment> fragmentList)
  {
    super(fm);
    this.fragmentList=fragmentList;
  }
  @Override
  public Fragment getItem(int position)
  {
    //在这里不处理position的原因是因为getItem方法在
    //instantiateItem方法中调用。只要在调用前处理
    //position即可，以免重复处理

    return fragmentList.get(position);
  }

  @Override
  public int getCount() 
  {
    return Integer.MAX_VALUE;
  }

  @Override
  public int getItemPosition(Object object) 
  {
    return super.getItemPosition(object);
  }

  @Override
  public Object instantiateItem(ViewGroup container, int position) 
  {
    //处理position。让数组下标落在[0,fragmentList.size)中，防止越界
    position = position % fragmentList.size();

    return super.instantiateItem(container, position);
  }

}

    Fragment a=new ReadFragment();
    Fragment b=new ReadFragment();
    Fragment c=new ReadFragment();
    Fragment d=new ReadFragment();

    list=new ArrayList<Fragment>();
    list.add(a);
    list.add(b);
    list.add(c);
    list.add(d);

    readViewPager.setAdapter(new adapter(getSupportFragmentManager(),list));

readViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener()
    {
      @Override
      public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
      {}

      @Override
      public void onPageSelected(int position)
      {
        //处理position。让position落在[0,fragmentList.size)中，防止数组越界
        position = position % list.size();
        ReadFragment fragment= (ReadFragment) list.get(position); //获得此时选中的fragment
        fragment.refreshState(); //翻页的时候每个页面需要改变的参数使用这个方法来实现，这个方法在ReadFragment里面，修饰器得使用public
        ...
      }

      @Override
      public void onPageScrollStateChanged(int state)
      {}
    });