如何从URL获取JSON

Question

我从url获取Json文件，并希望逐个节点显示来自json文件的数据，然后将数据保存到DATABASE中。我正在使用下面的代码，但不工作，请帮助我找到错误。我已经提到了清单文件中的Internet权限。我也加入我的LOGCAT。谢谢。

我的主要活动：

public class MainActivity extends Activity { 
    String url="maps.google.com/maps/api/geocode/json?latlng="+31.5279024+","+74.3495554; 
    JSONArray user = null; 
    private static final String TAG_USER = "results"; 
    private static final String TAG_address = "address_components" ; 
    private static final String TAG_addressLName = "long_name"; 
    private static final String TAG_addressSName= "short_name" ; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 

    // Creating new JSON Parser 
    JsonParser jParser = new JsonParser(); 

    // Getting JSON from URL 
    JSONObject json = jParser.getJSONFromUrl(url); 
    try { 
     // Getting JSON Array 
     user = json.getJSONArray(TAG_USER); 
     JSONObject c = user.getJSONObject(0); 
     // Storing JSON item in a Variable 
     String id = c.getString(TAG_address); 
     String name = c.getString(TAG_addressLName); 
     String email = c.getString(TAG_addressSName); 
     //Importing TextView 
     final TextView uid = (TextView)findViewById(R.id.uid); 
     final TextView name1 = (TextView)findViewById(R.id.name1); 
     final TextView email1 = (TextView)findViewById(R.id.email); 
     //Set JSON Data in TextView 
     uid.setText(id); 
     name1.setText(name); 
     email1.setText(email); 
    } catch (JSONException e) { 
    e.printStackTrace(); 
    } 
    } 


    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.main, menu); 
    return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 
    if (id == R.id.action_settings) { 
     return true; 
    } 
    return super.onOptionsItemSelected(item); 
    } 
} 

我的JSON类

包com.parsep.parse;

public class JsonParser { 

    static InputStream is = null; 
    static JSONObject jObj = null; 
    static String json = ""; 

    public JsonParser(){ 

    } 
    public JSONObject getJSONFromUrl(String url) 
    { 
     try 
     { 
      DefaultHttpClient httpClient= new DefaultHttpClient(); 
      HttpGet httpPost = new HttpGet(url); 
     // httpPost.setEntity(new UrlEncodedFormEntity(params)); 

      HttpResponse httpResponse = httpClient.execute(httpPost); 
      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, "iso-8859-1"), 8); 
      StringBuilder sb = new StringBuilder(); 
      String line = null; 
      while ((line = reader.readLine()) != null) { 
       sb.append(line + "\n"); 
      } 
      is.close(); 
      json = sb.toString(); 
      Log.e("JSON", json); 
     } catch (Exception e) { 
      Log.e("Buffer Error", "Error converting result " + e.toString()); 
     } 

     // try parse the string to a JSON object 
     try { 
      jObj = new JSONObject(json);    
     } catch (JSONException e) { 
      Log.e("JSON Parser", "Error parsing data " + e.toString()); 
     } 
     return jObj; 
    } 
    } 

我的logcat：

11-05 14:45:29.790: E/AndroidRuntime(533): FATAL EXCEPTION: main 
    11-05 14:45:29.790: E/AndroidRuntime(533): java.lang.RuntimeException: Unable to start activity    
    ComponentInfo{com.parsep.parse/com.parsep.parse.MainActivity}:    java.lang.IllegalStateException:  
    Target host must not be null, or set in parameters. scheme=null, host=null,    path=maps.google.com/maps/api/geocode/json 
    11-05 14:45:29.790: E/AndroidRuntime(533): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at android.app.ActivityThread.access$600(ActivityThread.java:123) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at android.os.Handler.dispatchMessage(Handler.java:99) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at android.os.Looper.loop(Looper.java:137) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at android.app.ActivityThread.main(ActivityThread.java:4424) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at java.lang.reflect.Method.invokeNative(Native Method) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at java.lang.reflect.Method.invoke(Method.java:511) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at dalvik.system.NativeStart.main(Native Method) 
    11-05 14:45:29.790: E/AndroidRuntime(533): Caused by: java.lang.IllegalStateException: Target host must not be null, or set in parameters. scheme=null, host=null, path=maps.google.com/maps/api/geocode/json 
    11-05 14:45:29.790: E/AndroidRuntime(533): at org.apache.http.impl.client.DefaultRequestDirector.determineRoute(DefaultRequestDirector.java:591) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:293) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at com.parsep.parse.JsonParser.getJSONFromUrl(JsonParser.java:40) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at  com.parsep.parse.MainActivity.onCreate(MainActivity.java:29) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at android.app.Activity.performCreate(Activity.java:4465) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 
    11-05 14:45:29.790: E/AndroidRuntime(533): at    android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920) 
    11-05 14:45:29.790: E/AndroidRuntime(533): ... 11 more 
    11-05 14:45:30.010: I/dalvikvm(533): threadid=3: reacting to signal 3 
    11-05 14:45:30.049: I/dalvikvm(533): Wrote stack traces to '/data/anr/traces.txt' 
    11-05 14:45:30.350: I/dalvikvm(533): threadid=3: reacting to signal 3 
    11-05 14:45:30.360: I/dalvikvm(533): Wrote stack traces to '/data/anr/traces.txt' 

Answer 1

我想你要的 “http：//” 添加到您的网址得到它的工作。

Answer 2

只需更换您的code.It以下行可能会有所帮助

public class MainActivity extends Activity { 
    String url="http://maps.google.com/maps/api/geocode/json?latlng="+31.5279024+","+74.3495554"; 
    JSONArray user = null; 

Answer 3

尝试用这种方式：

new AsyncTaskParseJson().execute(); // write this in onCreate(); method. 

    public class AsyncTaskParseJson extends AsyncTask<String, String, String> { 

      final String TAG = "AsyncTaskParseJson.java"; 

      // set your json string url here 
      String yourJsonStringUrl = "http://maps.google.com/maps/api/geocode/json?latlng="+31.5279024+","+74.3495554;; 

      // contacts JSONArray 
      JSONArray dataJsonArr = null; 

      @Override 
      protected void onPreExecute() {} 

      @Override 
      protected String doInBackground(String... arg0) { 

       try { 

        // instantiate our json parser 
        JsonParser jParser = new JsonParser(); 

        // get json string from url 
        JSONObject json = jParser.getJSONFromUrl(yourJsonStringUrl); 
        //Below parsing is just for your reference, do your task here. 
        // get the array of users 
        dataJsonArr = json.getJSONArray("Users"); 

        // loop through all users 
        for (int i = 0; i < dataJsonArr.length(); i++) { 

         JSONObject c = dataJsonArr.getJSONObject(i); 

         // Storing each json item in variable 
         String firstname = c.getString("firstname"); 
         String lastname = c.getString("lastname"); 
         String username = c.getString("username"); 

         // show the values in our logcat 
         Log.e(TAG, "firstname: " + firstname 
           + ", lastname: " + lastname 
           + ", username: " + username); 

        } 

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

       return null; 
      } 

      @Override 
      protected void onPostExecute(String strFromDoInBg) {} 
     } 
    } 

Answer 4

如果只想地址列表从LAT-长然后使用反向地理编码。

以这种方式调用下面的方法并获取数据。

Address address=getAddressListFromLatLong(YOUR LATITUDE, YOUR LONGITUDE); 
String country=address.getCountryName(); 
String address1=address.getAddressLine(1); 
Strin address2=address.getAddressLine(2); 
String postalCode=address.getPostalCode(); 

public static List<Address> getAddressListFromLatLong(double lat, double lng) { 
     geocoder = new Geocoder(YOUR ACTIVITY.this); 

     List<Address> list = null; 
     try { 
      list = geocoder.getFromLocation(lat, lng, 10); //10 is for results, you can use 1 if you want 1 result only. 
     } catch (Throwable e) { 
      e.printStackTrace(); 
     } 
     return list; 
    }