如何解析JSON对象并将其显示在列表视图中？

Question

以下是我遇到问题的代码。 php文件就像一个魅力一样，你可以看到你是否转到了url_all_dates变量所持有的值。这个类下面是list_item的.xml布局文件。该应用程序运行，但不会显示任何数据库：日期的

public class RequestTour extends ListActivity { 

    // Progress Dialog 
    private ProgressDialog pDialog; 

    // Creating JSON Parser object 
    JSONParser jParser = new JSONParser(); 

    ArrayList<HashMap<String, String>> datesList; 

    // url to get all dates list 
    private static String url_all_dates = "http://www.prayingmantesconcepts.com/androidfinal/get_all_avail_dates.php"; 

    // JSON Node names 
    private static final String TAG_SUCCESS = "success"; 
    private static final String TAG_DATES = "dates"; 
    private static final String TAG_DATEID = "dateID"; 
    private static final String TAG_DATE = "date"; 

    // dates JSONArray 
    JSONArray dates = null; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.dates);//put dates layout here. 

     // Hashmap for ListView 
     datesList = new ArrayList<HashMap<String, String>>(); 

     // Loading dates in Background Thread 
     new LoadAllDates().execute(); 

     // Get listview 
     ListView lv = getListView(); 

     // on seleting single date 
     // launching Book Tour Screen 
     lv.setOnItemClickListener(new OnItemClickListener() { 

      public void onItemClick(AdapterView<?> parent, View view, 
        int position, long id) { 
       // getting values from selected ListItem 
       String dateID = ((TextView) view.findViewById(R.id.dateID)).getText() 
         .toString(); 

       // Starting new intent 
       Intent in = new Intent(getApplicationContext(), 
         BookTour.class); 
       // sending dateID to next activity 
       in.putExtra(TAG_DATEID, dateID); 

       // starting new activity and expecting some response back 
       startActivityForResult(in, 100); 
      } 
     }); 

    } 

    // Response from Edit Product Activity 
    @Override 
    protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
     super.onActivityResult(requestCode, resultCode, data); 
     // if result code 100 
     if (resultCode == 100) { 
      // if result code 100 is received 
      // means user booked a tour 
      // reload this screen again 
      Intent intent = getIntent(); 
      finish(); 
      startActivity(intent); 
     } 

    } 

    /** 
    * Background Async Task to Load all dates by making HTTP Request 
    * */ 
    class LoadAllDates extends AsyncTask<String, String, String> { 

     /** 
     * Before starting background thread Show Progress Dialog 
     * */ 
     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      pDialog = new ProgressDialog(RequestTour.this); 
      pDialog.setMessage("Loading dates. Please wait..."); 
      pDialog.setIndeterminate(false); 
      pDialog.setCancelable(false); 
      pDialog.show(); 
     } 

     /** 
     * getting All dates from url 
     * */ 
     protected String doInBackground(String... args) { 
      // Building Parameters 
      List<NameValuePair> params = new ArrayList<NameValuePair>(); 
      // getting JSON string from URL 
      JSONObject json = jParser.makeHttpRequest(url_all_dates, "GET", params); 

      // Check your log cat for JSON response 
      Log.d("All Dates: ", json.toString()); 

      try { 
       // Checking for SUCCESS TAG 
       int success = json.getInt(TAG_SUCCESS); 

       if (success == 1) { 
        // found 
        // Getting Array of 
        dates = json.getJSONArray(TAG_DATES); 

        // looping through All Dates Available for Request 
        for (int i = 0; i < dates.length(); i++) { 
         JSONObject c = dates.getJSONObject(i); 

         // Storing each json item in variable 
         String id = c.getString(TAG_DATEID); 
         String date = c.getString(TAG_DATE); 

         // creating new HashMap 
         HashMap<String, String> map = new HashMap<String, String>(); 

         // adding each child node to HashMap key => value 
         map.put(TAG_DATEID, id); 
         map.put(TAG_DATE, date); 

         // adding HashList to ArrayList 
         datesList.add(map); 
        } 
       } else { 
        // no found 
        // Launch Add New product Activity 
        Intent i = new Intent(getApplicationContext(), 
          Main.class); 
        // Closing all previous activities 
        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 
        startActivity(i); 
       } 
      } catch (JSONException e) { 
       e.printStackTrace(); 
      } 

      return null; 
     } 

     /** 
     * After completing background task Dismiss the progress dialog 
     * **/ 
     protected void onPostExecute(String file_url) { 
      // dismiss the dialog after getting all 
      pDialog.dismiss(); 
      // updating UI from Background Thread 
      runOnUiThread(new Runnable() { 
       public void run() { 
        /** 
        * Updating parsed JSON data into ListView 
        * */ 
        ListAdapter adapter = new SimpleAdapter(
          RequestTour.this, datesList, 
          R.layout.list_item, new String[] { TAG_DATEID, 
            TAG_DATE}, 
          new int[] { R.id.dateID, R.id.date }); 
        // updating listview 
        setListAdapter(adapter); 
       } 
      }); 

     } 

    } 
} 


<!------------------------------------------------------------------------------------> 


list_item.xml: 

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:orientation="vertical" > 

    <!-- Date id (dateID) - will be HIDDEN - used to pass to other activity --> 
    <TextView 
     android:id="@+id/dateID" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:visibility="gone" /> 


    <!-- Date Label --> 
    <TextView 
     android:id="@+id/date" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:paddingTop="6dip" 
     android:paddingLeft="6dip" 
     android:textSize="17dip" 
     android:textStyle="bold" /> 

</LinearLayout> 

Answer 1

FIRST ISSUE： 这里

  // no found 
      // Launch Add New product Activity 
      Intent i = new Intent(getApplicationContext(), 
        Main.class); 
      // Closing all previous activities 
      i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 
      startActivity(i); 

您试图访问从后台线程.move UI元素在doInBackground完成之后，这些代码行用于onPostExecute用于从AsyncTask更新UI。

---

第二个问题：

这里

protected void onPostExecute(String file_url) { 
      // dismiss the dialog after getting all 
      pDialog.dismiss(); 
      // updating UI from Background Thread 
      runOnUiThread(new Runnable() { 
       public void run() { 
        /** 
        * Updating parsed JSON data into ListView 
        * */ 

       } 
      }); 

，因为我们能够访问UI元素的AsyncTaskonPostExecute方法，因此没有必要使用runOnUiThread针对你的情况更新中onPostExecute UI元素，比如你正尝试使用ListAdapter或ListView内runOnUiThreadonPostExecute

---

SOLUTION：

更改LoadAllDates代码，通过适当的方式使用AsyncTask：这里

class LoadAllDates extends AsyncTask<String, String, 
            ArrayList<HashMap<String, String>>> { 
    datesList=new ArrayList<HashMap<String, String>>; 
     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      //YOUR CODE HERE 
     } 


     protected ArrayList<HashMap<String, String>> 
           doInBackground(String... args) { 
     // Building Parameters 
     List<NameValuePair> params = new ArrayList<NameValuePair>(); 
     // getting JSON string from URL 
     JSONObject json = 
        jParser.makeHttpRequest(url_all_dates, "GET", params); 

      // Check your log cat for JSON response 
      Log.d("All Dates: ", json.toString()); 

      try { 
       // Checking for SUCCESS TAG 
       int success = json.getInt(TAG_SUCCESS); 

       if (success == 1) { 
        // found 
        // Getting Array of 
        dates = json.getJSONArray(TAG_DATES); 

        // looping through All Dates Available for Request 
        for (int i = 0; i < dates.length(); i++) { 
         JSONObject c = dates.getJSONObject(i); 

         // Storing each json item in variable 
         String id = c.getString(TAG_DATEID); 
         String date = c.getString(TAG_DATE); 

         // creating new HashMap 
         HashMap<String, String> map = 
            new HashMap<String, String>(); 

         // adding each child node to HashMap key => value 
         map.put(TAG_DATEID, id); 
         map.put(TAG_DATE, date); 

         // adding HashList to ArrayList 
         datesList.add(map); 
        } 
       } else { 
        // no found 

       } 
      } catch (JSONException e) { 
       e.printStackTrace(); 
      } 

      return ArrayList<HashMap<String, String>>; 
     } 

     /** 
     * After completing background task Dismiss the progress dialog 
     * **/ 
     protected void onPostExecute(
        ArrayList<HashMap<String, String>> file_url) { 
      // dismiss the dialog after getting all 
      pDialog.dismiss(); 
      // updating UI from Background Thread 

        if(file_url.size()>0) 
        { 
        ListAdapter adapter = new SimpleAdapter(
          RequestTour.this, file_url, 
          R.layout.list_item, new String[] { TAG_DATEID, 
            TAG_DATE}, 
          new int[] { R.id.dateID, R.id.date }); 
        // updating listview 
        setListAdapter(adapter); 
        } 
       else{ 
        // Launch Add New product Activity 
        Intent i = new Intent(getApplicationContext(), 
          Main.class); 
        // Closing all previous activities 
        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 
        startActivity(i); 
        } 


     } 

    } 

Answer 2

You have to use Gson Json parsing this is a good way to parse Json object 

eg: 

String json1 = "[{\"contactName\":\"3\",\"contactNumber\":\"3\"},{\"contactName\":\"4\",\"contactNumber\":\"4\"}]"; 

Gson gson = new Gson(); 
Type collectionType = new TypeToken<List<ContactDetail>>(){}.getType(); 
List<ContactDetail> details = gson.fromJson(json1, collectionType); 

Here ContactDetail class consists of String contactName and String contactNumber and their corresponding getters and setters. 
Note: make List<ContactDetail> details as a public static variable in your class and 
from your activity class pass this list object in your listview adapter. 

Answer 3

就是我的回答。希望能帮助到你。您也可以访问我解析的网址：http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.io.UnsupportedEncodingException; 
import java.net.URL; 
import java.util.ArrayList; 
import java.util.zip.GZIPInputStream; 

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

import android.app.Activity; 
import android.app.ListActivity; 
import android.graphics.Color; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.util.Log; 
import android.widget.ArrayAdapter; 
import android.widget.ListView; 

public class Courses extends Activity { 

    ArrayList<String> items = new ArrayList<String>(); 

    //URL requestUrl = new URL(url); 
    JSONArray courses = null; 
    //private static final String TAG_COURSES = "Courses"; 
    static JSONObject jObj = null; 
    static String json = ""; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.courses); 
     new MyTask().execute("http://redsox.tcs.auckland.ac.nz/734A/CSService.svc/courses"); 

    } 


    private class MyTask extends AsyncTask<String, Void, JSONObject> { 

     @Override 
     protected JSONObject doInBackground(String... urls) { 
      // return loadJSON(url); 
      String url = new String(urls[0]); 
      try { 

       // defaultHttpClient 
       DefaultHttpClient httpClient = new DefaultHttpClient(); 
       //HttpPost httpPost = new HttpPost(url); 
       HttpGet httpGet = new HttpGet(url); 
       HttpResponse httpResponse = httpClient.execute(httpGet); 

       HttpEntity httpEntity = httpResponse.getEntity(); 
       is = httpEntity.getContent(); 

      } catch (UnsupportedEncodingException e) { 
       e.printStackTrace(); 
      } catch (ClientProtocolException e) { 
       e.printStackTrace(); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
      try { 
      /*BufferedReader reader = new BufferedReader(new InputStreamReader(
        is, "UTF-8"), 8);*/ 
      InputStream inputStream = is; 
      GZIPInputStream input = new GZIPInputStream(inputStream); 
      InputStreamReader reader = new InputStreamReader(input); 
      BufferedReader in = new BufferedReader(reader); 
      StringBuilder sb = new StringBuilder(); 
      String line = null; 
      while ((line = in.readLine()) != null) { 
       sb.append(line); 
       //System.out.println(line); 
      } 
      is.close(); 
      json = sb.toString(); 
     } catch (Exception e) { 
      Log.e("Buffer Error", "Error converting result " + e.toString()); 
     } 

     // try parse the string to a JSON object 

     try { 

      JSONArray courses = new JSONArray(json); 
      //JSONArray people = new JSONArray(json); 
      for (int i = 0; i < courses.length(); i++) { 
       //System.out.println(courses.getJSONObject(i).toString()); 
       JSONObject c = courses.getJSONObject(i); 

       // Storing each json item in variable 
       String course_id = c.getString("codeField"); 
       String course_name = c.getString("titleField"); 
       String course_semester = c.getString("semesterField"); 

       items.add(course_id +"\n"+course_name+"\t"+course_semester); 

       /*Log.v("--", "Course:" + course_id + "\n Course Title: " + course_name 
         + "\n Semesters offered: " + course_semester);*/ 
      } 


      //jObj = new JSONObject(json); 
     } catch (JSONException e) { 
      Log.e("JSON Parser", "Error parsing data " + e.toString()); 
     } 


     // return JSON String 
     return jObj; 
     } 

     @SuppressWarnings("unchecked") 
     protected void onPostExecute(JSONObject json) { 
      ListView myListView = (ListView)findViewById(R.id.coursesList); 
      myListView.setAdapter(new ArrayAdapter(getApplicationContext(), android.R.layout.simple_list_item_1, items)); 

    } 
    } 




}