如何使用emply list加載Android中的listview，稍後內容將會下載？

Question

我需要加載列表中的加載文本，但首先它應該加載一個空列表，在那段時間它應該顯示一個進度條。我從JSON進紙器獲取所有內容。但是我堅持在進程處於背景時如何加載空列表。

/** 
* This class loads MainScreen in ListView 
*/ 
package com.smartmedia.salonaudi; 

import java.io.BufferedReader; 
import java.io.InputStreamReader; 
import java.net.HttpURLConnection; 
import java.net.URL; 
import java.util.ArrayList; 
import java.util.Arrays; 
import java.util.Comparator; 
import java.util.HashMap; 
import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 

import android.app.ListActivity; 
import android.app.ProgressDialog; 
import android.content.Context; 
import android.content.Intent; 
import android.net.ConnectivityManager; 
import android.net.NetworkInfo; 
import android.net.Uri; 
import android.os.Bundle; 
import android.os.Handler; 
import android.util.Log; 
import android.view.View; 
import android.view.Window; 
import android.widget.AdapterView; 
import android.widget.AdapterView.OnItemClickListener; 
import android.widget.Button; 
import android.widget.ListAdapter; 
import android.widget.ListView; 
import android.widget.SimpleAdapter; 

import com.smartmedia.salonaudi.map.GoogleMapActivityClass; 

/** 
* 
* 
* 
*/ 
public class SalonAudiActivity extends ListActivity { 

    Button map; 
    Button left; 
    Button about; 
    final Handler uiThreadCallback = new Handler(); 
    Runnable runInUIThread; 
    // WebView about; 

    ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>(); 
    ArrayList<HashMap<String, String>> mylistCopy = mylist; 
    ArrayList<String> latitude = new ArrayList<String>(); 
    ArrayList<String> longitude = new ArrayList<String>(); 

    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     requestWindowFeature(Window.FEATURE_NO_TITLE); 
     setContentView(R.layout.listplaceholder); 
     //processDialog = ProgressDialog.show(this, "", getString(R.string.loading), true); 
     // getDetails(); 
     // Map Button Click 
     map = (Button) findViewById(R.id.seeonmap); 

     map.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 

       Intent intent = new Intent(SalonAudiActivity.this, 
         GoogleMapActivityClass.class); 


       intent.putExtra("latitude", latitude); 
       intent.putExtra("longitude", longitude); 
       startActivity(intent); 
      } 
     }); 

     // Live Button Click 
     about = (Button) findViewById(R.id.about); 

     about.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Intent intent = new Intent(Intent.ACTION_VIEW, Uri 
         .parse("http://google.com")); 
       startActivity(intent); 

      } 
     }); 

     JSONObject json = JSONfunctions 
        .getJSONfromURL("http://audi.smart-media.no/api/getEvents.php"); 

      try { 

       JSONObject es = json.getJSONObject("events"); 
       JSONArray event = es.getJSONArray("event"); 
       JSONObject[] events = new JSONObject[es.length()]; 

       for (int i = 0; i < event.length(); i++) { 

        HashMap<String, String> map = new HashMap<String, String>(); 
        JSONObject e = event.getJSONObject(i); 
        map.put("id", String.valueOf(i)); 
        map.put("Time", "" + e.getString("startTime").split(" ")[0]); 
        map.put("startTime", 
          "" 
            + e.getString("startTime").split(" ")[1] 
              .substring(0, 5) 
            + " @ Olympic Stadium"); 

        map.put("title", "" + e.getString("title")); 
        System.out.println("title" + e.getString("title")); 
        map.put("ingress", "" + e.getString("ingress")); 
        map.put("description", 
          "" 
            + e.getString("description").replaceAll(
              "\\<[^>]*>", "")); 
        map.put("image", "" + e.getString("image")); 
        map.put("latitude", "" + e.getString("latitude")); 
        map.put("longitude", "" + e.getString("longitude")); 

        System.out.println("latitude" + e.getString("latitude")); 
        mylist.add(map); 

       } 

      } 

      catch (JSONException e) { 
       Log.e("log_tag", "Error parsing data " + e.toString()); 
      } 



     ListAdapter adapter = new SimpleAdapter(this, mylist, R.layout.main, 
       new String[] { "startTime", "title", "description" }, 
       new int[] { R.id.time, R.id.title, R.id.description }); 

     setListAdapter(adapter); 

     final ListView lv = getListView(); 

     lv.setTextFilterEnabled(true); 
     lv.setOnItemClickListener(new OnItemClickListener() { 
      @Override 
      public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, 
        long arg3) { 

       Intent intent = new Intent(); 
       intent.setClassName(SalonAudiActivity.this, 
         "com.smartmedia.salonaudi.DetailView"); 

       HashMap<String, String> map = mylistCopy.get(arg2); 
       intent.putExtra("title", map.get("title")); 
       intent.putExtra("image", map.get("image")); 
       intent.putExtra("startTime", map.get("startTime")); 
       intent.putExtra("ingress", map.get("ingress")); 
       intent.putExtra("description", map.get("description")); 
       startActivity(intent); 
      } 

     }); 

     for (int i = 0; i < mylist.size(); i++) { 
      HashMap<String, String> e = mylist.get(0); 
      latitude.add(e.get("latitude")); 
      longitude.add(e.get("longitude")); 
     } 
    } 

    public boolean isConnected() { 
     Context context = getApplicationContext(); 
     ConnectivityManager connectivity = (ConnectivityManager) context 
       .getSystemService(Context.CONNECTIVITY_SERVICE); 
     if (connectivity == null) { 

     } else { 
      NetworkInfo[] info = connectivity.getAllNetworkInfo(); 
      if (info != null) { 
       for (int i = 0; i < info.length; i++) { 
        if (info[i].getState() == NetworkInfo.State.CONNECTED) { 
         return true; 
        } 
       } 
      } 
     } 
     return false; 
    } 

} 

Answer 1

在列表中加載數據時，您必須使用AsyncTask來顯示對話框。

無疑這將解決你的問題

有代碼...這將幫助你做你的工作......

在doInBackground方法加載所有烏爾JSON數據到數組或ArrayList和設置成在adpater

在PostExecute方法，設置適配器列表..如果可能的

private class LoadingData extends AsyncTask<String, Void, String> { 

     private ProgressDialog Dialog = new ProgressDialog(getParent()); 

     @Override 
     protected String doInBackground(String... params) { 
     // perform long running operation operation 
     //Here you have to do your network operations.. 

     return null; 
     } 


     @Override 
     protected void onPostExecute(String result) { 
     // execution of result of Long time consuming operation 

     try 
      { 
        if(Dialog.isShowing()) 
        { 
         Dialog.dismiss(); 
        } 
        // do your Display and data setting operation here 
      } 
      catch(Exception e) 
      { 

      } 
     //Here depending upon your validation, display appropriate message. 
      } 

     @Override 
      protected void onPreExecute() { 
      Dialog.setMessage("Loading Data....."); 
      Dialog.show(); 

     // Things to be done before execution of long running operation. For example showing ProgessDialog 

     } 

     @Override 
     protected void onProgressUpdate(Void... values) { 
     // Things to be done while execution of long running operation is in progress. For example updating ProgessDialog 
     } 
    }