问题描述

Android，Fragment使用AsyncHttpClient数据不显示

先贴代码：
NewsFragment.java

public class NewsFragment extends Fragment {    private final static String TAG = ""NewsFragment"";    Activity activity;    ArrayList<NewsEntity> newsList = new ArrayList<NewsEntity>();    HeadListView mListView;    NewsAdapter mAdapter;    int channel_id;    ImageView detail_loading;    public final static int SET_NEWSLIST = 0;    /** 此方法意思为fragment是否可见 可见时候加载数据 */    @Override    public void setUserVisibleHint(boolean isVisibleToUser) {   //onCreateView之前调用的        if (isVisibleToUser) {            System.out.println(""isVisibleToUser"");            System.out.println(channel_id);            if (channel_id == 0) {                channel_id = 1;            }            initData();            //fragment可见时加载数据            if(newsList !=null && newsList.size() !=0){                System.out.println(""newList not null"");                handler.obtainMessage(SET_NEWSLIST).sendToTarget();            }else{                System.out.println(""newList null"");                new Thread(new Runnable() {                    @Override                    public void run() {                        try {                            Thread.sleep(2);                        } catch (InterruptedException e) {                            e.printStackTrace();                        }                        handler.obtainMessage(SET_NEWSLIST).sendToTarget();                    }                }).start();            }        }else{            System.out.println(""isNotVisibleToUser"");            //fragment不可见时不执行操作        }        super.setUserVisibleHint(isVisibleToUser);    }//  OnPageChangeListener    @Override    public void onAttach(Activity activity) {        System.out.println(""news_frag_onAttach"");        this.activity = activity;        super.onAttach(activity);    }    @Override    public void onCreate(Bundle savedInstanceState) {        System.out.println(""news_frag_onCreate"");        Bundle args = getArguments();       //传值//      text = args != null ? args.getString(""text"") : """";        channel_id = args != null ? args.getInt(""id"" 0) : 0;        System.out.println(""NewsFragment_channel_id:""+channel_id);        if (getUserVisibleHint()) {            System.out.println(""onCreate_getUserVisibleHint"");        }        super.onCreate(savedInstanceState);    }    @SuppressLint(""InflateParams"")    @Override    public View onCreateView(LayoutInflater inflater ViewGroup container            Bundle savedInstanceState) {        System.out.println(""news_frag_onCreateView"");        View view = LayoutInflater.from(getActivity()).inflate(R.layout.news_fragment null);        mListView = (HeadListView) view.findViewById(R.id.mListView);        detail_loading = (ImageView)view.findViewById(R.id.detail_loading);        return view;    }    private void initData() {        //newsList.clear();        newsList = Constants2.getNewsList(channel_id);    }    @SuppressLint(""HandlerLeak"")    Handler handler = new Handler() {        @Override        public void handleMessage(Message msg) {            System.out.println(""handler:""+msg.what);            switch (msg.what) {            case SET_NEWSLIST:                detail_loading.setVisibility(View.GONE);                if(mAdapter == null){                    mAdapter = new NewsAdapter(activity newsList);                    //判断是不是城市的频道                    if(channel_id == Constants2.CHANNEL_CITY){                        //是城市频道                        mAdapter.setCityChannel(true);                        initCityChannel();                    }                }                mListView.setAdapter(mAdapter);                mListView.setOnScrollListener(mAdapter);                mListView.setPinnedHeaderView(LayoutInflater.from(activity).inflate(R.layout.list_item_section mListView false));                mListView.setOnItemClickListener(new OnItemClickListener() {                    @Override                    public void onItemClick(AdapterView<?> parent View view                            int position long id) {                        Intent intent = new Intent(activity DetailsActivity.class);                        if(channel_id == Constants2.CHANNEL_CITY){                            if(position != 0){                                intent.putExtra(""news"" mAdapter.getItem(position - 1));                                startActivity(intent);                                activity.overridePendingTransition(R.anim.slide_in_right R.anim.slide_out_left);                            }                        }else{                            intent.putExtra(""news"" mAdapter.getItem(position));                            startActivity(intent);                            activity.overridePendingTransition(R.anim.slide_in_right R.anim.slide_out_left);                        }                    }                });                break;            default:                break;            }            super.handleMessage(msg);        }    };    /* 初始化选择城市的header*/    @SuppressLint(""InflateParams"")    public void initCityChannel() {        View headview = LayoutInflater.from(activity).inflate(R.layout.city_category_list_tip null);        TextView chose_city_tip = (TextView) headview.findViewById(R.id.chose_city_tip);        chose_city_tip.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(activity CityListActivity.class);                startActivity(intent);            }        });        mListView.addHeaderView(headview);    }    /* 摧毁视图 */    @Override    public void onDestroyView() {        super.onDestroyView();        Log.d(""onDestroyView""channel_id = "" + channel_id);        mAdapter = null;    }    /* 摧毁该Fragment，一般是FragmentActivity 被摧毁的时候伴随着摧毁 */    @Override    public void onDestroy() {        super.onDestroy();        Log.d(TAGchannel_id = "" + channel_id);    }}

Contants2.java

 public class Constants2 {    public static final String GET_NEWS_URL = AppApplication.NEWS_URL+""/getNewsJSON.php"";    public static final String GET_Comment_URL = AppApplication.NEWS_URL+""/commentlist.php"";    static ArrayList<NewsEntity> newsList = new ArrayList<NewsEntity>();    static ArrayList<CommentEntity> commentList = new ArrayList<CommentEntity>();    static JSONArray jsonArray;    static JSONArray commentJsonArray;    /*     * 获取新闻列表     */    public static ArrayList<NewsEntity> getNewsList(int channel_id) {        AsyncHttpClient client = new AsyncHttpClient();        RequestParams params = new RequestParams();        params.add(""channel_id"" String.valueOf(channel_id));        System.out.println(""Constants2_channel_id:""+String.valueOf(channel_id));        client.post(GET_NEWS_URL params new AsyncHttpResponseHandler() {            @Override            public void onSuccess(int i Header[] handler byte[] bytes) {                String response = new String(bytes);                Log.e(""debug""response:""+response);                try {                    jsonArray = new JSONArray(response);                } catch (JSONException e) {                    System.err.println(""newslist_jsonArray_error"");                    e.printStackTrace();                }            }            @Override            public void onFailure(int arg0 Header[] arg1 byte[] arg2 Throwable arg3) {                System.out.println(""数据错误!!"");            }        });        if (jsonArray != null) {            System.out.println(""/////////////////////////"");            System.out.println(jsonArray.length());            newsList.clear();            for(int i =0 ; i < jsonArray.length() ; i++){                try {                    JSONObject obj = jsonArray.getJSONObject(i);                    NewsEntity news = new NewsEntity();                    news.setId(i);                    news.setNewsId(obj.getString(""newsId""));                    news.setCollectStatus(false);                    news.setCommentNum(i + 10);                    news.setInterestedStatus(true);                    news.setLikeStatus(true);                    news.setReadStatus(false);                    news.setNewsCategory(""推荐"");                    news.setNewsCategoryId(1);                    news.setSource_url("""");                    news.setTitle(obj.getString(""title""));                    List<String> url_list = new ArrayList<String>();                    news.setPicOne(obj.getString(""pic_url""));                    url_list.add(obj.getString(""pic_url""));                    news.setPicList(url_list);                    news.setReporter(obj.getString(""reporter""));                    news.setPublishTime(obj.getString(""time""));                    news.setReadStatus(false);                    news.setSource(""手机腾讯网"");                    news.setContent(obj.getString(""content""));                    news.setSummary(""腾讯数码讯（编译：Gin）谷歌眼镜可能是目前最酷的可穿戴数码设备，你可以戴着它去任何地方（只要法律法规允许或是没有引起众怒），作为手机的第二块“增强现实显示屏”来使用。另外，虽然它仍未正式销售，但谷歌近日在美国市场举行了仅限一天的开放购买活动，价格则为1500美元（约合人民币9330元），虽然仍十分昂贵，但至少可以满足一些尝鲜者的需求，也预示着谷歌眼镜的公开大规模销售离我们越来越近了。"");                    news.setMark(i);                    news.setIsLarge(false);                    if(i == 2){                        news.setComment(""评论部分，说的非常好。"");                    }//                  news.setPublishTime(Long.valueOf(obj.getString(""time"")));                    if(i <= 2){                        news.setPublishTime(DateTools.getTime());                    }else if(i >2 && i <= 5){                        news.setPublishTime(String.valueOf(Long.valueOf(DateTools.getTime()) - 86400));                    }else{                        news.setPublishTime(String.valueOf(Long.valueOf(DateTools.getTime()) - 86400 * 2));                    }                    newsList.add(news);                } catch (JSONException e) {                    e.printStackTrace();                }            }        }        return newsList;    }}

流程是这样：
当前fragment可视时通过initData()加载数据，就是调用Constants2的getNewsList(channel_id) 方法，_该方法执行异步任务返回一个newsList现在的问题是首次加载的时候数据显示，请问有什么解决方法？

解决方案

要能有数据就奇怪了，使用了多线程，不在网络线程执行完成后初始化数据，怎么跟主线程同步起来

解决方案二：
client.post(GET_NEWS_URL params new AsyncHttpResponseHandler()
这个是异步的，所 以你直接返回的肯定是空的值；
你需要在 success中处理把得到的值，直接给newsList 再进行adapter.notifyDataSetChanged()刷新就可以了；

mAdapter = null; 这个最好去掉，不需要，还有可能造成异常；