Android: unable to retrieve data from json

问题:

I am getting one id of some event from the previous activity to this activity and passing this id to the url in current activity to get cityname present in that url. My code is..

String s = getIntent().getStringExtra("ar");

try{          
    HttpPost hpost = new HttpPost("xxxxxxxxxxxxxxxxx/id");
    HttpResponse response = login.client.execute(hpost);
    List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(1);
    nameValuePairs.add(new BasicNameValuePair("id", s));
    hpost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
    String re = EntityUtils.toString(response.getEntity());
    System.out.print(re);

    JSONObject root = new JSONObject(re);  
    eveState.setText(root.getString("cityname"));  
}
catch(Exception e){
    Log.e("exvcx", "error getting data" +e.toString());
}

The exception I am getting is that no value for cityname. I think I am unable to pass the id to this url..Please tell is this the right method? If yes please provide solution to the problem otherwise please correct me where I am doing wrong. Thanks.

{"status":1,"response":[{"id":"73","name":"Dangerous","address":"Rydgggh","location":"Entry try","phnumber":"2467568","createdate":"2012-07-11 06:24:31","image":"4ffd626f021487.45227344.jpg","block":"n","deleted":"n","cityname":"Juneau","statename":"Alaska","interestname":"Comedy","username":"princeb","eventdate":"2012-07-13 15:45:29","formatteddate":"July 13, 2012"}],"imageWidth":1024,"imageHeight":1024}

回答1:

Please refer this answer i have given in below question

https://stackoverflow.com/a/11260845/1441666

I have this array

{
"result": "success",
"countryCodeList":
[
  {"countryCode":"00","countryName":"World Wide"},
  {"countryCode":"kr","countryName":"Korea"}
] 
}

Here below I am fetching country details

JSONObject json = new JSONObject(jsonstring);
JSONArray nameArray = json.names();
JSONArray valArray = json.toJSONArray(nameArray);

JSONArray valArray1 = valArray.getJSONArray(1);

valArray1.toString().replace("[", "");
valArray1.toString().replace("]", "");

int len = valArray1.length();

for (int i = 0; i < valArray1.length(); i++) {

 Country country = new Country();
 JSONObject arr = valArray1.getJSONObject(i);
 country.setCountryCode(arr.getString("countryCode"));                        
 country.setCountryName(arr.getString("countryName"));
 arrCountries.add(country);
}

回答2:

problems i noticed are :

• you set the id parameter after executing the HTTPPost request.
• not reading the response from the server input stream. have you tried to print the read data to console and verified it is the correct one.

use the read function below

public static JSONObject read(String url, String id){

    InputStream is = null;
    String result = "";
    // http post
    try {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(url);

        List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(1);
        nameValuePairs.add(new BasicNameValuePair("id", id));
        httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
        HttpResponse response = httpclient.execute(httppost);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();

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

    // convert response to string
    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();
        result = sb.toString();

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

    JSONObject jsonObject=null;
    try {
        jsonObject = new JSONObject(result);
    } catch (JSONException e) {
        e.printStackTrace();
    }

    return jsonObject;
}

• now you will get the JSON string wrapped in a JSONObject
• now traverse this object to get the cityname

code sample

try {
    JSONObject jsonObject = new JSONObject(json);
    JSONArray jsonArray = jsonObject.optJSONArray("response");
    String cityName = ((JSONObject)jsonArray.get(0)).getString("cityname");
    System.out.println("Cityname : "+cityName);
} catch (JSONException e2) {
    e2.printStackTrace();
}