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