求助一个比较难的问题

package com.gift.android.travel.fragment;



import java.util.ArrayList;



import java.util.List;

import android.content.Context;

import android.os.Bundle;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.MotionEvent;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

import android.widget.GridView;

import android.widget.ImageView;

import com.gift.android.R;

import com.gift.android.Utils.HttpUtils;

import com.gift.android.Utils.ImageCache;

import com.gift.android.Utils.Utils;

import com.gift.android.travel.fragment.base.BaseTravelFragment;

import com.gift.android.travel.model.PhotoWallJson;

import com.gift.android.travel.model.PhotoWallList;



import com.gift.android.widget.pulltorefreshlistview.PullToRefreshBase;

import com.gift.android.widget.pulltorefreshlistview.PullToRefreshBase.OnRefreshListener2;

import com.gift.android.widget.pulltorefreshlistview.PullToRefreshGridView;

import com.google.gson.Gson;



/**

 * 目的地 -照片墙

 * 

 * @author duanzheng

 * 

 */



public class microtravelDetailiInfoPhotoWallFragment extends BaseTravelFragment

		implements OnRefreshListener2<GridView> {

	private LayoutInflater inflater;

	private View mtdipw;

	private PullToRefreshGridView gv;



	private int pageIndex = 1;

	private int pageSize = 15;



	private gvadapter adapter;

	private PhotoWallJson photoWallJson;

	private List<PhotoWallList> list;



	@Override

	public View onCreateView(LayoutInflater inflater, ViewGroup container,

			Bundle savedInstanceState) {

		// TODO Auto-generated method stub

		this.inflater = inflater;

		mtdipw = inflater.inflate(

				R.layout.microtravel_detaili_info_photowall_fragment, null);

		return super.onCreateView(inflater, container, savedInstanceState);

	}



	@Override

	public void onViewCreated(View view, Bundle savedInstanceState) {

		// TODO Auto-generated method stub

		setContentView(mtdipw);

		findbyid();

		initView();

		getDate(true);

		super.onViewCreated(view, savedInstanceState);

	}



	private void getDate(boolean isStartAnimator) {

		String args = String.format("&destId=%s&version=%s", "3559", "1.0.0");

		if (isStartAnimator) {

			loading.doGet(

					"http://192.168.0.64/api/router/rest.do?method=api.com.trip.dest.pic"

							+ args, "api.com.trip.dest.pic", 0, "", this);

		} else {

			HttpUtils.getInstance().doGet(

					"http://192.168.0.64/api/router/rest.do?method=api.com.trip.dest.pic"

							+ args, "api.com.trip.dest.pic", 0, "", this);

		}



	}



	public void requestFinished(String response, String method) {

		Log.i("test", "response:" + response);



		Gson gson = new Gson();

		photoWallJson = gson.fromJson(response, PhotoWallJson.class);



		if (photoWallJson.code == 1) {

			if (photoWallJson.data != null && photoWallJson.data.list != null

					&& photoWallJson.data.list.size() > 0) {

				

				Log.i("test", "更新前list:" + list.size());

				//for(int i=0;i<30;i++){

				list.addAll(photoWallJson.data.list);

				//}

				Log.i("test", "更新后list:--->" + list.size());

				gv.setLastPage(photoWallJson.data.hasNext);

				if (!photoWallJson.data.hasNext) {

					pageIndex++;

				}

				Log.i("test", "开始更新数据");

				adapter.notifyDataSetChanged();//这一行执行后不会更新，list已经改变

			}

		}



		gv.onRefreshComplete();

	}



	public void requestFailure(Throwable t, String method) {

		if (gv != null) {

			gv.onRefreshComplete();

		}

		Utils.showToast(getActivity(), R.drawable.face_fail,

				"哎呀，网络不给力\n请稍后再试试吧", 0);

	}



	private void initView() {

		list = new ArrayList<PhotoWallList>();



		adapter = new gvadapter(getActivity(), list);

		gv.setAdapter(adapter);



		gv.setOnRefreshListener(this);



	}



	private void findbyid() {

		gv = (PullToRefreshGridView) mtdipw.findViewById(R.id.gv);

	}



	class gvadapter extends BaseAdapter {

		private Context mContext;

		// private List<PhotoWallList> list = new ArrayList<PhotoWallList>();



		/*

		 * public List<PhotoWallList> getList() { return list; }

		 */

		private List<PhotoWallList> mList;



		public gvadapter(Context context, List<PhotoWallList> list) {

			super();

			Log.i("test", "进来:" + list.size());

			this.mContext = context;

			this.mList = list;

			// TODO Auto-generated constructor stub

		}



		@Override

		public int getCount() {

			// TODO Auto-generated method stub

			//return (mList != null ? mList.size() : 0);

			return (mList != null && mList.size()>0 ? 20 : 0);

		}



		@Override

		public Object getItem(int position) {

			// TODO Auto-generated method stub

			return mList.get(position);

		}



		@Override

		public long getItemId(int position) {

			// TODO Auto-generated method stub

			return 0;

		}



		@Override

		public View getView(int position, View convertView, ViewGroup parent) {

			ViewHolder holder;

			if (convertView == null) {

				holder = new ViewHolder();

				convertView = View.inflate(mContext,

						R.layout.microtravel_detaili_info_photowall_item, null);

				holder.iv = (ImageView) convertView.findViewById(R.id.iv);

				convertView.setTag(holder);

			} else {

				holder = (ViewHolder) convertView.getTag();

			}



			/*ImageCache

					.display(

							"http://s0.hao123img.com/res/r/image/2014-09-23/0e348339febbb4eb0c3ceeba26067a1b.jpg",

							holder.iv, R.drawable.coverdefault);*/

			

			holder.iv.setBackgroundResource(R.drawable.coverdefault_170);



			

			return convertView;

		}



	}



	class ViewHolder {

		ImageView iv;

	}



	@Override

	public void onPullDownToRefresh(PullToRefreshBase<GridView> refreshView) {

		// TODO Auto-generated method stub

		getDate(false);

		pageIndex = 1;

	}



	@Override

	public void onPullUpToRefresh(PullToRefreshBase<GridView> refreshView) {

		// TODO Auto-generated method stub

		if (gv.isLastPage()) {

			gv.onRefreshComplete();

		} else {

			getDate(false);

		}

	}



}

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical" >



    <View

        android:layout_width="fill_parent"

        android:layout_height="1dp"

        android:background="#F1F1F1" />



    <com.gift.android.widget.pulltorefreshlistview.PullToRefreshGridView xmlns:ptr="http://schemas.android.com/apk/res/com.gift.android"

        android:id="@+id/gv"

        android:layout_width="fill_parent"

        android:layout_height="fill_parent"

        android:gravity="center"

        android:horizontalSpacing="5dp"

        android:listSelector="@null"

        android:numColumns="3"

        android:scrollbars="none"

        android:verticalSpacing="5dp"

        ptr:ptrMode="both" >

    </com.gift.android.widget.pulltorefreshlistview.PullToRefreshGridView>



</LinearLayout>