The application's PagerAdapter changed the adapter's contents without calling notifyDataSetChanged

The application’s PagerAdapter changed the adapter’s contents without calling PagerAdapter#notifyDataSetChanged

今天开发的时候遇到如题所述的异常，找了一下在satckoverflow上看到一个比较靠谱的答案：

After ADT 22 the PagerAdapter has gotten very strict about calling notifyDataSetChanged() before calling getCount(). It evidently keeps track of what it thinks the count should be and if this is not the same as what getCount() returns it throws this exception. So the solution is simply to call notifyDataSetChanged() on the adapter every time the size of the data changes.

在adt22之后，PagerAdapter对于notifyDataSetChanged()和getCount()的执行顺序是非常严格的，系统跟踪count的值，如果这个值和getCount返回的值不一致，就会抛出这个异常。所以为了保证getCount总是返回一个正确的值，那么在初始化ViewPager时，应先给Adapter初始化内容后再将该adapter传给ViewPager，如果不这样处理，在更新adapter的内容后，应该调用一下adapter的notifyDataSetChanged方法。

在初始化ViewPager时，应先给Adapter初始化内容后再将该adapter传给ViewPager，如果不这样处理，在更新adapter的内容后，应该调用一下adapter的notifyDataSetChanged方法，否则在ADT22以上使用会报The application’s PagerAdapter changed the adapter’s contents without calling PagerAdapter#notifyDataSetChanged的异常，具体原因可参考：http://stackoverflow.com/questions/16756131/fragmentstatepageradapter-stopped-working-after-updating-to-adt-22

package com.itheima.zhbj52.base;

import java.util.ArrayList;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Color;
import android.os.Handler;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.text.TextUtils;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
import android.widget.TextView;
import android.widget.Toast;

import com.google.gson.Gson;
import com.itheima.zhbj52.NewsDetailActivity;
import com.itheima.zhbj52.R;
import com.itheima.zhbj52.domain.NewsData.NewsTabData;
import com.itheima.zhbj52.domain.TabData;
import com.itheima.zhbj52.domain.TabData.TabNewsData;
import com.itheima.zhbj52.domain.TabData.TopNewsData;
import com.itheima.zhbj52.global.GlobalContants;
import com.itheima.zhbj52.utils.CacheUtils;
import com.itheima.zhbj52.utils.PrefUtils;
import com.itheima.zhbj52.utils.bitmap.MyBitmapUtils;
import com.itheima.zhbj52.view.RefreshListView;
import com.itheima.zhbj52.view.RefreshListView.OnRefreshListener;
import com.lidroid.xutils.BitmapUtils;
import com.lidroid.xutils.HttpUtils;
import com.lidroid.xutils.ViewUtils;
import com.lidroid.xutils.exception.HttpException;
import com.lidroid.xutils.http.ResponseInfo;
import com.lidroid.xutils.http.callback.RequestCallBack;
import com.lidroid.xutils.http.client.HttpRequest.HttpMethod;
import com.lidroid.xutils.view.annotation.ViewInject;
import com.viewpagerindicator.CirclePageIndicator;

/**
 * 页签详情页
 * 
 * @author Kevin
 * 
 */
public class TabDetailPager extends BaseMenuDetailPager implements
        OnPageChangeListener {

    NewsTabData mTabData;
    private TextView tvText;

    private String mUrl;
    private TabData mTabDetailData;

    @ViewInject(R.id.vp_news)
    private ViewPager mViewPager;

    @ViewInject(R.id.tv_title)
    private TextView tvTitle;// 头条新闻的标题
    private ArrayList mTopNewsList;// 头条新闻数据集合

    @ViewInject(R.id.indicator)
    private CirclePageIndicator mIndicator;// 头条新闻位置指示器

    @ViewInject(R.id.lv_list)
    private RefreshListView lvList;// 新闻列表
    private ArrayList mNewsList; // 新闻数据集合
    private NewsAdapter mNewsAdapter;
    private String mMoreUrl;// 更多页面的地址

    private Handler mHandler;

    public TabDetailPager(Activity activity, NewsTabData newsTabData) {
        super(activity);
        mTabData = newsTabData;
        mUrl = GlobalContants.SERVER_URL + mTabData.url;
    }

    @Override
    public View initViews() {
        View view = View.inflate(mActivity, R.layout.tab_detail_pager, null);
        // 加载头布局
        View headerView = View.inflate(mActivity, R.layout.list_header_topnews,
                null);

        ViewUtils.inject(this, view);
        ViewUtils.inject(this, headerView);

        // 将头条新闻以头布局的形式加给listview
        lvList.addHeaderView(headerView);

        // 设置下拉刷新监听
        lvList.setOnRefreshListener(new OnRefreshListener() {

            @Override
            public void onRefresh() {
                getDataFromServer();
            }

            @Override
            public void onLoadMore() {
                if (mMoreUrl != null) {
                    getMoreDataFromServer();
                } else {
                    Toast.makeText(mActivity, "最后一页了", Toast.LENGTH_SHORT)
                            .show();
                    lvList.onRefreshComplete(false);// 收起加载更多的布局
                }
            }
        });

        lvList.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView parent, View view,
                    int position, long id) {
                System.out.println("被点击:" + position);
                // 35311,34221,34234,34342
                // 在本地记录已读状态
                String ids = PrefUtils.getString(mActivity, "read_ids", "");
                String readId = mNewsList.get(position).id;
                if (!ids.contains(readId)) {
                    ids = ids + readId + ",";
                    PrefUtils.setString(mActivity, "read_ids", ids);
                }

                // mNewsAdapter.notifyDataSetChanged();
                changeReadState(view);// 实现局部界面刷新, 这个view就是被点击的item布局对象

                // 跳转新闻详情页
                Intent intent = new Intent();
                intent.setClass(mActivity, NewsDetailActivity.class);
                intent.putExtra("url", mNewsList.get(position).url);
                mActivity.startActivity(intent);
            }
        });

        return view;
    }

    /**
     * 改变已读新闻的颜色
     */
    private void changeReadState(View view) {
        TextView tvTitle = (TextView) view.findViewById(R.id.tv_title);
        tvTitle.setTextColor(Color.GRAY);
    }

    @Override
    public void initData() {
        String cache = CacheUtils.getCache(mUrl, mActivity);

        if (!TextUtils.isEmpty(cache)) {
            parseData(cache, false);
        }

        getDataFromServer();
    }

    private void getDataFromServer() {
        HttpUtils utils = new HttpUtils();
        utils.send(HttpMethod.GET, mUrl, new RequestCallBack() {

            @Override
            public void onSuccess(ResponseInfo responseInfo) {
                String result = (String) responseInfo.result;
                System.out.println("页签详情页返回结果:" + result);

                parseData(result, false);

                lvList.onRefreshComplete(true);

                // 设置缓存
                CacheUtils.setCache(mUrl, result, mActivity);
            }

            @Override
            public void onFailure(HttpException error, String msg) {
                Toast.makeText(mActivity, msg, Toast.LENGTH_SHORT).show();
                error.printStackTrace();

                lvList.onRefreshComplete(false);
            }
        });
    }

    /**
     * 加载下一页数据
     */
    private void getMoreDataFromServer() {
        HttpUtils utils = new HttpUtils();
        utils.send(HttpMethod.GET, mMoreUrl, new RequestCallBack() {

            @Override
            public void onSuccess(ResponseInfo responseInfo) {
                String result = (String) responseInfo.result;

                parseData(result, true);

                lvList.onRefreshComplete(true);
            }

            @Override
            public void onFailure(HttpException error, String msg) {
                Toast.makeText(mActivity, msg, Toast.LENGTH_SHORT).show();
                error.printStackTrace();
                lvList.onRefreshComplete(false);
            }
        });
    }

    protected void parseData(String result, boolean isMore) {
        Gson gson = new Gson();
        mTabDetailData = gson.fromJson(result, TabData.class);
        System.out.println("页签详情解析:" + mTabDetailData);

        // 处理下一页链接
        String more = mTabDetailData.data.more;
        if (!TextUtils.isEmpty(more)) {
            mMoreUrl = GlobalContants.SERVER_URL + more;
        } else {
            mMoreUrl = null;
        }

        if (!isMore) {
            mTopNewsList = mTabDetailData.data.topnews;

            mNewsList = mTabDetailData.data.news;

            if (mTopNewsList != null) {
                mViewPager.setAdapter(new TopNewsAdapter());
                mIndicator.setViewPager(mViewPager);
                mIndicator.setSnap(true);// 支持快照显示
                mIndicator.setOnPageChangeListener(this);

                mIndicator.onPageSelected(0);// 让指示器重新定位到第一个点

                tvTitle.setText(mTopNewsList.get(0).title);
            }

            if (mNewsList != null) {
                mNewsAdapter = new NewsAdapter();
                lvList.setAdapter(mNewsAdapter);
            }

            // 自动轮播条显示
            if (mHandler == null) {
                mHandler = new Handler() {
                    public void handleMessage(android.os.Message msg) {
                        int currentItem = mViewPager.getCurrentItem();

                        if (currentItem < mTopNewsList.size() - 1) {
                            currentItem++;
                        } else {
                            currentItem = 0;
                        }

                        mViewPager.setCurrentItem(currentItem);// 切换到下一个页面
                        mHandler.sendEmptyMessageDelayed(0, 3000);// 继续延时3秒发消息,
                                                                    // 形成循环
                    };
                };

                mHandler.sendEmptyMessageDelayed(0, 3000);// 延时3秒后发消息
            }

        } else {// 如果是加载下一页,需要将数据追加给原来的集合
            ArrayList news = mTabDetailData.data.news;
            mNewsList.addAll(news);
            mNewsAdapter.notifyDataSetChanged();
        }
    }

    /**
     * 头条新闻适配器
     * 
     * @author Kevin
     * 
     */
    class TopNewsAdapter extends PagerAdapter {

        private BitmapUtils utils;

        public TopNewsAdapter() {
            utils = new BitmapUtils(mActivity);
            utils.configDefaultLoadingImage(R.drawable.topnews_item_default);// 设置默认图片
        }

        @Override
        public int getCount() {
            return mTabDetailData.data.topnews.size();//修改为mTopNewsList.size();
        }

        @Override
        public boolean isViewFromObject(View arg0, Object arg1) {
            return arg0 == arg1;
        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            ImageView image = new ImageView(mActivity);
            image.setScaleType(ScaleType.FIT_XY);// 基于控件大小填充图片

            TopNewsData topNewsData = mTopNewsList.get(position);
            utils.display(image, topNewsData.topimage);// 传递imagView对象和图片地址

            container.addView(image);

            image.setOnTouchListener(new TopNewsTouchListener());// 设置触摸监听

            return image;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((View) object);
        }
    }

    /**
     * 头条新闻的触摸监听
     * 
     * @author Kevin
     * 
     */
    class TopNewsTouchListener implements OnTouchListener {

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                System.out.println("按下");
                mHandler.removeCallbacksAndMessages(null);// 删除Handler中的所有消息
                // mHandler.postDelayed(new Runnable() {
                //
                // @Override
                // public void run() {
                //
                // }
                // }, 3000);
                break;
            case MotionEvent.ACTION_CANCEL:
                System.out.println("事件取消");
                mHandler.sendEmptyMessageDelayed(0, 3000);
                break;
            case MotionEvent.ACTION_UP:
                System.out.println("抬起");
                mHandler.sendEmptyMessageDelayed(0, 3000);
                break;

            default:
                break;
            }

            return true;
        }

    }

    /**
     * 新闻列表的适配器
     * 
     * @author Kevin
     * 
     */
    class NewsAdapter extends BaseAdapter {

        private BitmapUtils utils;

        // private MyBitmapUtils utils;

        public NewsAdapter() {
            utils = new BitmapUtils(mActivity);
            utils.configDefaultLoadingImage(R.drawable.pic_item_list_default);
            // utils = new MyBitmapUtils();
        }

        @Override
        public int getCount() {
            return mNewsList.size();
        }

        @Override
        public TabNewsData getItem(int position) {
            return mNewsList.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder holder;
            if (convertView == null) {
                convertView = View.inflate(mActivity, R.layout.list_news_item,
                        null);
                holder = new ViewHolder();
                holder.ivPic = (ImageView) convertView
                        .findViewById(R.id.iv_pic);
                holder.tvTitle = (TextView) convertView
                        .findViewById(R.id.tv_title);
                holder.tvDate = (TextView) convertView
                        .findViewById(R.id.tv_date);

                convertView.setTag(holder);
            } else {
                holder = (ViewHolder) convertView.getTag();
            }

            TabNewsData item = getItem(position);

            holder.tvTitle.setText(item.title);
            holder.tvDate.setText(item.pubdate);

            utils.display(holder.ivPic, item.listimage);

            String ids = PrefUtils.getString(mActivity, "read_ids", "");
            if (ids.contains(getItem(position).id)) {
                holder.tvTitle.setTextColor(Color.GRAY);
            } else {
                holder.tvTitle.setTextColor(Color.BLACK);
            }

            return convertView;
        }

    }

    static class ViewHolder {
        public TextView tvTitle;
        public TextView tvDate;
        public ImageView ivPic;
    }

    @Override
    public void onPageScrollStateChanged(int arg0) {

    }

    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {

    }

    @Override
    public void onPageSelected(int arg0) {
        TopNewsData topNewsData = mTopNewsList.get(arg0);
        tvTitle.setText(topNewsData.title);
    }
}

原因：在加载下一页的时候，mTabDetailData.data.topnews.size()会发生变化，即PagerAdapter的getCount()会发生变化；解决办法：在数据发生变化的时候调用PagerAdapter#notifyDataSetChanged()

TopNewsAdapter mTopNewsAdapter;
...
mViewPager.setAdapter(new TopNewsAdapter());
mIndicator.setViewPager(mViewPager);
...
ArrayList news = mTabDetailData.data.news;
mNewsList.addAll(news);
mNewsAdapter.notifyDataSetChanged();