仅在选中时如何在 ViewPager 中加载片段

I'm using 3 Fragments inside a Viewpager, the problem is that I am loading big data in an Asynctask and loaders. On devices like HTC one, it works fine, however, on low-end devices, it takes a lot of time. This is mainly because when I implement the pagerAdapter, I put the Fragments inside an ArrayList, this force the fragments instantiate when the main activity is loaded. What I need is that it just "load" the first fragment (main) and when the user Swype, load the other fragment. its any way to achieve this? this is my pageAdapater

public class PagerAdapter extends FragmentPagerAdapter  {

    private final ArrayList<Fragment> mFragments = new ArrayList<Fragment>();
   // private final ArrayList<String> titulos = new ArrayList<String>();

   // private int NUM_PAGES =0;
    public PagerAdapter(FragmentManager manager,int num_pages) {
        super(manager);
     //   this.NUM_PAGES = num_pages;
    }


    public void addFragment(Fragment fragment,String title) {
        mFragments.add(fragment);
            notifyDataSetChanged();
    }

    @Override
    public int getCount() {
        //return NUM_PAGES;
       return mFragments.size();
    }

    @Override
    public Fragment getItem(int position) {
        return mFragments.get(position);

    }

} 

推荐答案

Sun 的上述方法对我不起作用(也许对你有用)，但我想我也会分享我对他方法的编辑.顺便说一句Sun，很好的方法！

private boolean _hasLoadedOnce= false; // your boolean field

@Override
public void setUserVisibleHint(boolean isFragmentVisible_) {
    super.setUserVisibleHint(true);


    if (this.isVisible()) {
        // we check that the fragment is becoming visible
        if (isFragmentVisible_ && !_hasLoadedOnce) {
            new NetCheck().execute();
            _hasLoadedOnce = true;
        }
    }
}