Question

我正在使用Android工作室安装android项目我正在使用Web服务我在从数据库中获取数据并显示此数据时遇到问题（测试我使用后端，我有“getProspectServlet” 所以我有一个名为prospecti的表需要获取潜在客户列表并在展开的列表中显示潜在客户，这是从数据库中获取潜在客户并将其存储在“liste”列表中的类的代码

import android.app.Activity;
import android.content.Context;
import android.os.AsyncTask;
import android.util.Log;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.Toast;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

/**
 * Created by DKTIQUE on 19/05/2016.
 */
public class getProspect extends AsyncTask<Void,Void,String> {
    private Context context;
    List<Prospect> liste;

    public List<Prospect> getListe() {
        return liste;
    }
    // ProgressBar pb;

    public getProspect(Context context) {
        this.context = context;
    }



  /*  public getProspect(Context context, List<Prospect> liste) {
        this.context = context;
        this.liste = liste;
    }*/

    /*  @Override
    protected void onPreExecute() {
        pb = (ProgressBar) ((Activity)context).findViewById(R.id.progressBar);
        pb.setVisibility(View.VISIBLE);
    }*/

    @Override
    protected String doInBackground(Void... params) { // c un tableau

        String data;
        StringBuilder result= new StringBuilder();

        try {
           // URL url = new URL ("http://10.0.2.163:8080/Prospects/GET");
           URL url = new URL ("http://192.168.43.249:8080/getProspect");

          //  URL url = new URL ("http://10.0.19.196:8080/getProspect");

           // URL url = new URL ("http:// 10.0.19.196:8080/Prospects/GET");


            HttpURLConnection httpURLConnection=(HttpURLConnection) url.openConnection();
            httpURLConnection.setConnectTimeout(5000);
            InputStream is = httpURLConnection.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
            while ((data = reader.readLine()) != null) {
                result.append(data);
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
       Log.v("resut", result.toString());
        return result.toString();
    }

    @Override
    protected void onPostExecute(String s) {//afficher le resultat
       // List<Prospect>
                liste = new ArrayList<>();
//        pb.setVisibility(View.VISIBLE);

        // Gson gson = new Gson();
        // if (!s.equals("")) {

        try {
            JSONArray jsonArray = new JSONArray(s);

            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject jsonObject = jsonArray.getJSONObject(i);
                Prospect prospect= new Prospect();
                prospect.setNom(jsonObject.get("nom").toString());
                prospect.setPrenom(jsonObject.get("prenom").toString());
               // prospect.setTitle(jsonObject.get("idProspect").toString());

               ListeProspect.listee.add(prospect);
               liste.add(prospect);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }


        if (ListeProspect.listee.size()==0){Toast.makeText(context,"emptyyyyyyyyyyy",Toast.LENGTH_SHORT).show();}
        // TextView textView = (Activity)context.findViewbyId();
    /*  for(int i=0;i<liste.size();i++){

           Toast.makeText(context,liste.get(i).getNom(), Toast.LENGTH_SHORT).show();
        }*/
    }

    //   }
}

我想得到这个列表对象并在这个列表中显示它们但是我在ListProspect中有一个空列表在getProspect中列表不是空的（我用吐司测试）但是当我尝试在ListProspect中获取列表时一无所获你可以看到我也使用了ListProspect中的静态列表来获取前景，但它也是空的我也使用了getListe（）这里是listView的代码

public class ListeProspect extends AppCompatActivity {

    static List<Prospect> listee = new ArrayList();

        ExpandableListAdapter listAdapter;
        ExpandableListView expListView;
        List<String> listDataHeader;
        HashMap<String, List<String>> listDataChild;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_liste_prospect);
//******************************************************

       // getProspect p= new getProspect(this).execute();
       // getProspect p= new getProspect(this);

     new getProspect(this).execute();
         //p = new getProspect(this);
        // p.execute();
       // p.onPostExecute();

        if (ListeProspect.listee.size()==0){Toast.makeText(this,"empty",Toast.LENGTH_SHORT).show();}

        else{Toast.makeText(this,"not empty",Toast.LENGTH_SHORT).show();
            for(int i=0;i<ListeProspect.listee.size();i++){

                Toast.makeText(this,ListeProspect. listee.get(i).getPrenom(), Toast.LENGTH_SHORT).show();
            }


        }





// get the listview
        expListView = (ExpandableListView) findViewById(R.id.lvExp);

        // preparing list data
        prepareListData();

        listAdapter = new ExpandableListAdapter(this, listDataHeader, listDataChild);

        // setting list adapter
        expListView.setAdapter(listAdapter);

        // Listview Group click listener
        expListView.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {

            @Override
            public boolean onGroupClick(ExpandableListView parent, View v,
                                        int groupPosition, long id) {
                // Toast.makeText(getApplicationContext(),
                // "Group Clicked " + listDataHeader.get(groupPosition),
                // Toast.LENGTH_SHORT).show();
                return false;
            }
        });

        // Listview Group expanded listener
        expListView.setOnGroupExpandListener(new ExpandableListView.OnGroupExpandListener() {

            @Override
            public void onGroupExpand(int groupPosition) {
                Toast.makeText(getApplicationContext(),
                        listDataHeader.get(groupPosition) + " Expanded",
                        Toast.LENGTH_SHORT).show();
            }
        });

        // Listview Group collasped listener
        expListView.setOnGroupCollapseListener(new ExpandableListView.OnGroupCollapseListener() {

            @Override
            public void onGroupCollapse(int groupPosition) {
                Toast.makeText(getApplicationContext(),
                        listDataHeader.get(groupPosition) + " Collapsed",
                        Toast.LENGTH_SHORT).show();

            }
        });

        // Listview on child click listener
        expListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {

            @Override
            public boolean onChildClick(ExpandableListView parent, View v,
                                        int groupPosition, int childPosition, long id) {
                // TODO Auto-generated method stub
                Toast.makeText(
                        getApplicationContext(),
                        listDataHeader.get(groupPosition)
                                + " : "
                                + listDataChild.get(
                                listDataHeader.get(groupPosition)).get(
                                childPosition), Toast.LENGTH_SHORT)
                        .show();
                return false;
            }
        });
    }

    /*
     * Preparing the list data
     */
    private void prepareListData() {
        listDataHeader = new ArrayList<String>();
        listDataChild = new HashMap<String, List<String>>();

        // Adding child data
        listDataHeader.add("Prospect 1");
        listDataHeader.add("Prospect 2");
        listDataHeader.add("Prospect 3");

        // Adding child data
        List<String> top250 = new ArrayList<String>();
        top250.add("Age1");
        top250.add("Assuré1");
        top250.add("Type de stomie1");
        top250.add("Nombre de poche par jour");


        List<String> nowShowing = new ArrayList<String>();
        nowShowing.add("Age2");
        nowShowing.add("Assuré");
        nowShowing.add("Type de stomie");
        nowShowing.add("Nombre de poche par jour");


        List<String> comingSoon = new ArrayList<String>();
        comingSoon.add("Age");
        comingSoon.add("Assuré");
        comingSoon.add("Type de stomie");
        comingSoon.add("Nombre de poche par jour");


        listDataChild.put(listDataHeader.get(0), top250); // Header, Child data
        listDataChild.put(listDataHeader.get(1), top250); // Header, Child data
        listDataChild.put(listDataHeader.get(2), top250); // Header, Child data
      //  listDataChild.put(listDataHeader.get(1), nowShowing);
       // listDataChild.put(listDataHeader.get(2), comingSoon);
    }
}

我怎么能解决这个问题就像我在课堂上说的“getProspect”我可以在祝酒词中展示我的前景但是当我去“ListeProspect”时我有空列表

Answer 1

检查它时列表显示为空的原因是因为您在后台线程上运行的asyncTask中填充它，并在调用主线程上的asyncTask后立即检查它。因此，在您尝试显示或打印出来之前，您无需让后台任务完成填充列表。 onPostExecute在主线程上运行，并在doInBackground完成后运行，因此在后台任务完成onPostExecute后，您可以执行任何操作。

Cricket也是正确的，使用静态变量来做这样的事情是没有必要的。如果您需要从另一个活动访问列表值，则通过意图传递它们。

在ListView中显示数据库中的数据

1 个答案: