ListView不显示JSON数据

我正在创建一个使用web服务的android应用程序，其中提供地名将搜索邮政编码并显示在ListView中。但我的ListView不显示来自服务器的JSON数据。请指点..ListView不显示JSON数据

MainActivity.java `

public class MainActivity extends AppCompatActivity { 
    private EditText etSearch; 
    private ListView lv; 
    private ProgressDialog progressDialog; 

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

     etSearch = (EditText) findViewById(R.id.editText); 
     lv = (ListView) findViewById(R.id.listView); 
    } 

    public void onClick(View view){ 
     String place = etSearch.getText().toString(); 
     if(place.length()>0){ 
      progressDialog = ProgressDialog.show(MainActivity.this,"Postal Code Search","Please Wait"); 
      SearchTask task = new SearchTask(); 
      task.execute(place); 
     }else { 
      Toast.makeText(this,"Please enter place Name",Toast.LENGTH_LONG).show(); 
     } 
    } 
    private ArrayList<String> searchResult = new ArrayList<>(); 

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

     @Override 
     protected JSONObject doInBackground(String... params) { 
      JSONObject result = null; 
      String placeName = params[0]; 

      try { 
       String urlS = "http://api.geonames.org/postalCodeSearchJSON?placename=" 
         + URLEncoder.encode(placeName, "UTF-8") 
         + "&maxRows=10&username=USERNAME"; 

       URL url = new URL(urlS); 
       HttpURLConnection connection = (HttpURLConnection) url.openConnection(); 
       connection.setReadTimeout(15000); 
       connection.setConnectTimeout(15000); 
       BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream())); 
       String resp = reader.readLine(); 
       Log.d("result",resp); 
       result = new JSONObject(resp); 
      } catch (Exception e){ 
       Log.e("SearchTask", "Error:"+e.getMessage()); 
      } 
      return result; 
     } 

     @Override 
     protected void onPostExecute(JSONObject response) { 
      progressDialog.cancel(); 
      searchResult.clear(); 
      if(response != null){ 
       try{ 
        JSONArray postalCodes = response.getJSONArray("postalCodes"); 
        for (int i=0;i<postalCodes.length();i++){ 
         JSONObject obj = postalCodes.getJSONObject(i); 
         String postalCode = obj.getString("postalCode"); 
         String placeName = obj.getString("placeName"); 
         searchResult.add("PlaceName: "+placeName+"\nPostalCode: "+postalCode); 
        } 
        if(searchResult.isEmpty()){ 
         searchResult.add("No postal code Found"); 
         ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,searchResult); 
         lv.setAdapter(adapter); 
         adapter.notifyDataSetChanged(); 
        } 
       } catch (JSONException je){ 
        Toast.makeText(MainActivity.this,"Parsing Error:"+je.getMessage(),Toast.LENGTH_LONG).show(); 
       } 
      } else { 
       Toast.makeText(MainActivity.this,"Couldn't Find",Toast.LENGTH_LONG).show(); 
      } 

     } 
    } 

} 
`

这是UI的一部分。 Activity.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    tools:context="com.example.priya.geocodeapp.MainActivity" 

    android:weightSum="1"> 

    <TextView 
     android:id="@+id/textView" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_weight="0.25" 
     android:text="Search Postal Code " 
     android:textAlignment="center" 
     android:textColor="@android:color/holo_blue_bright" 
     android:textSize="14sp" 
     android:textStyle="bold" 
     android:typeface="sans" /> 

    <EditText 
     android:id="@+id/editText" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_weight="0.07" 
     android:ems="10" 
     android:hint="Enter Place Name" 
     android:inputType="textPersonName" 
     android:textSize="14sp" 
     android:layout_marginTop="29dp" 
     android:layout_below="@+id/textView" 
     android:layout_alignParentEnd="true" /> 

    <Button 
     android:id="@+id/button" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_gravity="center" 
     android:layout_weight="0.05" 
     android:gravity="center" 
     android:onClick="onClick" 
     android:text="Search" 
     android:layout_marginTop="18dp" 
     android:layout_below="@+id/editText" 
     android:layout_centerHorizontal="true" /> 

    <ListView 
     android:id="@+id/listView" 
     android:layout_width="wrap_content" 
     android:layout_height="333dp" 

     android:layout_marginTop="34dp" 
     android:layout_below="@+id/button" 
     android:layout_alignParentStart="true" /> 


</RelativeLayout>`

JSON数据及其班加罗尔，例如，例如

{ 
    "postalCodes":[ 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore North", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.59443998336792, 
     "countryCode":"IN", 
     "postalCode":"560001", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Bangalore G.P.O.", 
     "lat":12.991448503615459 
     }, 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore North", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.59443998336792, 
     "countryCode":"IN", 
     "postalCode":"560001", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Bangalore Bazaar", 
     "lat":12.991448503615459 
     }, 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore North", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.59443998336792, 
     "countryCode":"IN", 
     "postalCode":"560001", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Rajbhavan (Bangalore)", 
     "lat":12.991448503615459 
     }, 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore South", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.59368896484375, 
     "countryCode":"IN", 
     "postalCode":"560002", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Bangalore Corporation Building", 
     "lat":12.97194016928975 
     }, 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore North", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.12604139137574, 
     "countryCode":"IN", 
     "postalCode":"560009", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Bangalore Dist Offices Bldg", 
     "lat":13.0642536587272 
     }, 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore North", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.54905700683594, 
     "countryCode":"IN", 
     "postalCode":"560010", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Industrial Estate (Bangalore)", 
     "lat":12.984736805762962 
     }, 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore South", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.5673389434814, 
     "countryCode":"IN", 
     "postalCode":"560018", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Chamrajpet (Bangalore)", 
     "lat":12.9603975402696 
     }, 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore North", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.54813032113138, 
     "countryCode":"IN", 
     "postalCode":"560024", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Anandnagar (Bangalore)", 
     "lat":12.971373314490803 
     }, 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore North", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.640380859375, 
     "countryCode":"IN", 
     "postalCode":"560038", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Indiranagar (Bangalore)", 
     "lat":12.974282086640057 
     }, 
     { 
     "adminCode2":"572", 
     "adminName3":"Bangalore North", 
     "adminCode1":"19", 
     "adminName2":"Bangalore", 
     "lng":77.32035308234025, 
     "countryCode":"IN", 
     "postalCode":"560040", 
     "adminName1":"Karnataka", 
     "ISO3166-2":"KA", 
     "placeName":"Vijayanagar (Bangalore)", 
     "lat":13.00637724835858 
     } 
    ] 
}

它应该在ListView中显示这个JSON数据。该程序运行良好，没有任何错误。 JSON数据显示在logcat中，但不显示在ListView中。我搜索了所有的stackoverflow解决方案，但没有为我工作。

来源

2017-03-22 Priyanka

你的逻辑错了，你正在检查你的数据是否为空。改变你的代码是这样的：

if(!searchResult.isEmpty()){ 

         ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,searchResult); 
         lv.setAdapter(adapter); 
         adapter.notifyDataSetChanged(); 
        }

使用“！”改变布尔值

来源

2017-03-22 13:14:58

您只能使用ArrayAdapter adapter = new ArrayAdapter （MainActivity.this，android.R.layout.simple_list_item_1，searchResult）; lv.setAdapter（adapter）;之后，你可以运行你的应用程序没有任何条件，如果工作，然后写任何条件。 –

其工作Luiz Fernando Salvaterra。但最后显示“找不到数据” – Priyanka

谢谢你Ranjeet。它在删除if块并仅使用ArrayAdapter之后工作。 – Priyanka

ListView不显示JSON数据

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