FragmentStatePagerAdapter的使用

1、两点

getItemPosition的覆写使notifyDataSetChanged();会根据数据源的变动更新，不过是全部重新加载，和ListView不一样

为了从外界(Activity)操作当前的fragment界面，使用了SparseArray<WeakReference<Fragment>>将当前的fragment实例存起来。

public class WillPagerAdapter extends FragmentStatePagerAdapter {
// SparseArray是Hashmap的改良品，其核心是折半查找函数（binarySearch）
SparseArray<WeakReference<Fragment>> registeredFragments = new SparseArray<WeakReference<Fragment>>();
private List<Will> mList;

public WillPagerAdapter(FragmentManager fm) {
super(fm);
}

public WillPagerAdapter(FragmentManager fm, List<Will> list) {
this(fm);
// TODO Auto-generated constructor stub
mList = list;
}

/*
* 生成新的 Fragment 对象。 .instantiateItem() 在大多数情况下，都将调用 getItem() 来生成新的对象
*/
@Override
public Fragment getItem(int position) {
// TODO Auto-generated method stub
WillFragment fragment = WillFragment.newInstance(mList.get(position));
return fragment;
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
// TODO Auto-generated method stub
// 得到缓存的fragment
WillFragment fragment = (WillFragment) super.instantiateItem(container,
position);
WeakReference<Fragment> weak = new WeakReference<Fragment>(fragment);
registeredFragments.put(position, weak);
return fragment;
}

@Override
public int getCount() {
// TODO Auto-generated method stub
return mList.size();
}

@Override
public void destroyItem(ViewGroup container, int position, Object object) {
// TODO Auto-generated method stub
registeredFragments.remove(position);

super.destroyItem(container, position, object);

}

/**
* 要求getItemPosition、FragmentStatePagerAdapter
*/
public void remove(int position) {
mList.remove(position);
notifyDataSetChanged();
}

@Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}public WillFragment getRegisteredFragment(int position) {
return (WillFragment) registeredFragments.get(position).get();
}
}

Done