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我在片段中有一个列表视图。问题是每次我打开该片段时它都会重新加载。

我从网上的列表中获取信息，因此每次下载并构建列表都是一个真正的问题。

那是我的代码：

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import com.example.free.MainActivity.Load;

import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.Toast;

public class ListActivity extends ListFragment {

    public void ToastLoadShout(String msg) {
        Toast.makeText(getActivity(), msg.toString(), Toast.LENGTH_LONG).show();
    }
    private static View View;

    HttpClient client;
    HttpPost httppost;
    HttpGet httpget;
    JSONObject json;
    List<List<String>> items;
    List<item> markers = new ArrayList<item>();

    MobileArrayAdapter adapter;

    ListView list;
    ProgressBar listload;
    Button relist;

    Preferences pref;

    String datadata = "";

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        if (View != null) {
            ViewGroup parent = (ViewGroup) View.getParent();
            if (parent != null)
                parent.removeView(View);
        }
        View = inflater.inflate(R.layout.activity_list, container, false);

        return View;
    }

    @Override
    public void onStart() {
        super.onStart();

//      pref = new Preferences(getActivity());
//      
//      listload = (ProgressBar) getView().findViewById(R.id.listload);
//      
//      relist = (Button) getView().findViewById(R.id.relist);
//      relist.setOnClickListener(new OnClickListener() {
//          public void onClick(View v) {
//              listload.setVisibility(View.INVISIBLE);
//              if (adapter!=null)
//              adapter.deleteList();
//              HashMap<String, String> loc = pref.getData();
//              ToastLoadShout(loc.get(Preferences.LAT) + ","
//                      + loc.get(Preferences.LON));
//              if (loc.get(Preferences.LAT) != "0.0"
//                      && loc.get(Preferences.LAT) != null)
//                  new Load().execute();
//              else
//                  ToastLoadShout("Get Location First.");
//          }});

    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        try {
            pref = new Preferences(getActivity());
            list = (ListView) getView().findViewById(android.R.id.list);
            listload = (ProgressBar) getView().findViewById(R.id.listload);
            HashMap<String, String> loc = pref.getData();
            ToastLoadShout(loc.get(Preferences.LAT) + ","
                    + loc.get(Preferences.LON));
            if (loc.get(Preferences.LAT) != "0.0"
                    && loc.get(Preferences.LAT) != null)
                new Load().execute();
            else
                ToastLoadShout("Get Location First.");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {

        // get selected items
        //String selectedValue = (String) getListAdapter().getItem(position);
        String selectedValue = markers.get(position).getTitle();
        Toast.makeText(getActivity(), selectedValue, Toast.LENGTH_SHORT).show();

    }



    class Load extends AsyncTask<String, Integer, Boolean> {
        @Override
        protected void onPreExecute() {
            listload.setVisibility(View.VISIBLE);
        }

        @Override
        protected Boolean doInBackground(String... params) {

            try {
                items = DownloadList();
                if (items != null)
                    return true;

            } catch (Exception e) {
                e.printStackTrace();
                return false;
            }
            return false;
        }

        @Override
        protected void onPostExecute(Boolean res) {
            // TODO Auto-generated method stub
            if (res) {
                ArrangePutMarkers();
                adapter=new MobileArrayAdapter(getActivity(), markers);
                list.setAdapter(adapter);
//              ToastLoadShout(Integer.parseInt(items.get(0).get(0))/* id */+","+ items
//                      .get(1).get(0)/* title */+","+ Integer.parseInt(items
//                      .get(2).get(0))/* cat */+","+ Integer
//                      .parseInt(items.get(3).get(0))/* program */+","+
//              items.get(4).get(0)/* desc */+","+
//              items.get(5).get(0)/* pub */+","+ Integer.parseInt(items
//                      .get(6).get(0))/* view */+","+ Integer
//                      .parseInt(items.get(7).get(0))/* like */+","+ Integer
//                      .parseInt(items.get(8).get(0))/* upvote */+","+
//              Integer.parseInt(items.get(9).get(0))/* downvote */+","+
//              Double.parseDouble(items.get(10).get(0))/* lat */+","+
//              Double.parseDouble(items.get(11).get(0))/* lon */);
            } else {
                ToastLoadShout("Error");
                ToastLoadShout(datadata);
            }
            listload.setVisibility(View.INVISIBLE);
        }
    }

    public void ArrangePutMarkers() {
        if (items != null) {
            for (int i = 0; i < items.get(0).size(); i++) {
                markers.add(new item(
                        Integer.parseInt(items.get(0).get(i))/* id */, items
                                .get(1).get(i)/* title */, Integer.parseInt(items
                                .get(2).get(i))/* cat */, Integer
                                .parseInt(items.get(3).get(i))/* program */,
                        items.get(4).get(i)/* desc */,
                        items.get(5).get(i)/* pub */, Integer.parseInt(items
                                .get(6).get(i))/* view */, Integer
                                .parseInt(items.get(7).get(i))/* like */, Integer
                                .parseInt(items.get(8).get(i))/* upvote */,
                        Integer.parseInt(items.get(9).get(i))/* downvote */,
                        Double.parseDouble(items.get(10).get(i))/* lat */,
                        Double.parseDouble(items.get(11).get(i))/* lon */));

            }
        }
    }

    public void onBackPressed() {

    }

}

这里有什么问题？

4

1 回答 1

0

onActivityCreated()每次实例化 Fragment 时都会调用（以及当设备在横向和纵向之间旋转时）。您正在此方法中创建列表数据的新实例。

您应该在 Fragment 外部（可能在您的 Activity 中）保留对列表的静态引用，这样您就不会每次都生成新列表，而只是使用您已经创建的现有列表。

于 2013-10-21T19:59:04.840 回答