給定字符串時，JSONArray無法轉換為JSONObject

Question

我遇到了JSON請求的問題。 我正在嘗試讀取API並使用此代碼解析它（如下所示）。 我已經讓異步工作（到目前為止）一旦我得到這個我應該設置。 我得到的錯誤在日志中。

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;

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.util.Log;


public class jsonParser {

    //initialize
    static InputStream stream = null;
    static String result = " ";
    static JSONObject object =null;

    public jsonParser(){

    }

    public JSONObject getJSONfromURL (String url){
        //HTTP call
        try{
            URLConnection connection = new URL(url).openConnection();

            BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()), 2048 * 16);
            StringBuffer builder = new StringBuffer();
            String line;

            while ((line = reader.readLine()) != null) {
              builder.append(line).append("\n");
            }
            String blah = builder.toString();
            JSONObject jsonObj = new JSONObject(new String(blah));
            JSONArray data = jsonObj.getJSONArray("Categories");

            for(int i=0; i < data.length(); i++)
            {
                 object = data.getJSONObject(i);
                 String id = object.getString("id"); 
                 String value = object.getString("name"); 
                 Log.d("Item name: ", value);
            }




            } catch(Exception e){
                Log.e("Http Error","Error in http connection " + e.toString());

            }


        return object;
    }
}

錯誤日志如下

05-12 02:49:44.553: E/Http Error(19288): Error in http connection org.json.JSONException: Value ["Categories",[[{"id":"2","name":"Glass Repair"},{"id":"3","name":"Appliance Repair"},{"id":"4","name":"Air Conditioning"},{"id":"5","name":"Community Involvement"},{"id":"6","name":"Electrical"},{"id":"7","name":"Flooring"},{"id":"8","name":"Heating Repair"},{"id":"9","name":"Landscaping"},{"id":"10","name":"Plumbing"},{"id":"11","name":"Remodeling\/Renovation"},{"id":"12","name":"Window Coverings"}]]] of type org.json.JSONArray cannot be converted to JSONObject
05-12 02:49:44.553: W/dalvikvm(19288): threadid=1: thread exiting with uncaught exception (group=0x40fb6438)
05-12 02:49:44.563: E/AndroidRuntime(19288): FATAL EXCEPTION: main
05-12 02:49:44.563: E/AndroidRuntime(19288): java.lang.NullPointerException
05-12 02:49:44.563: E/AndroidRuntime(19288):    at com.example.hstnc_activity.DisplayServiceActivity$Request.onPostExecute(DisplayServiceActivity.java:116)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at com.example.hstnc_activity.DisplayServiceActivity$Request.onPostExecute(DisplayServiceActivity.java:1)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at android.os.AsyncTask.finish(AsyncTask.java:631)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at android.os.AsyncTask.access$600(AsyncTask.java:177)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at android.os.Handler.dispatchMessage(Handler.java:99)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at android.os.Looper.loop(Looper.java:137)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at android.app.ActivityThread.main(ActivityThread.java:4918)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at java.lang.reflect.Method.invokeNative(Native Method)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at java.lang.reflect.Method.invoke(Method.java:511)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771)
05-12 02:49:44.563: E/AndroidRuntime(19288):    at dalvik.system.NativeStart.main(Native Method)

這就是我應該通過服務器回來處理的問題

["Categories",[[{"id":"2","name":"Glass Repair"},{"id":"3","name":"Appliance Repair"},{"id":"4","name":"Air Conditioning"},{"id":"5","name":"Community Involvement"},{"id":"6","name":"Electrical"},{"id":"7","name":"Flooring"},{"id":"8","name":"Heating Repair"},{"id":"9","name":"Landscaping"},{"id":"10","name":"Plumbing"},{"id":"11","name":"Remodeling\/Renovation"},{"id":"12","name":"Window Coverings"}]]]

Answer 1

http://www.json.org/javadoc/org/json/JSONArray.html

嘗試

JSONArray jsonArray = new JSONArray(new String(blah));

代替

JSONObject jsonObj = new JSONObject(new String(blah));

您問題中的JSON示例實際上是一個JSON數組。

因此，它將會是

...
    public JSONObject getJSONfromURL (String url){
        //HTTP call
        try{
            URLConnection connection = new URL(url).openConnection();

            BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()), 2048 * 16);
            StringBuffer builder = new StringBuffer();
            String line;

            while ((line = reader.readLine()) != null) {
              builder.append(line).append("\n");
            }
            String blah = builder.toString();

            //Parsing string into JSONArray
            JSONArray data = new JSONArray(new String(blah));


            for(int i=0; i < data.length(); i++)
            {
                 object = data.getJSONObject(i);
                 String id = object.getString("id"); 
                 String value = object.getString("name"); 
                 Log.d("Item name: ", value);
            }




            } catch(Exception e){
                Log.e("Http Error","Error in http connection " + e.toString());

            }


        return object;
    }


..

---

以下是對JSON數據發生了什么的一些解釋。 目前它看起來像：

["Categories",[[{"id":"2","name":"Glass Repair"} ....

JSONObject jsonObj = new JSONObject(new String(blah));
JSONArray data = jsonObj.getJSONArray("Categories");

不會起作用，因為此JSON數據中沒有名為“Categories”的對象，而是具有值為“Categories”的String元素。

你真正應該做的是改進你的JSON表示

 {"Categories":[{"id":"2","name":"Glass Repair"} .... }

因此，解析器可以找出名為“Categories”的JSON對象。

以下是關於編寫JSON語法的建議。

http://en.wikipedia.org/wiki/JSON

此外，這里還有一個JSON驗證工具，可以快速調試/糾正JSON語法

http://jsonlint.com/

Answer 2

你必須考慮兩件事：

1. json響應對應於JSONArray而不是JSONObject 。
2. 根據您的響應格式，json響應中的"Categories"條目不是JSONArray 。

你應該試試這個。

JSONObject rawJson = new JSONObject ( jsonResponse );
JSONArray categories = rawJson.getJSONArray( "Categories" );

用這種json格式

{"Categories":[{"id":"2","name":"Glass Repair"},{"id":"3","name":"Appliance Repair"},{"id":"4","name":"Air Conditioning"},{"id":"5","name":"Community Involvement"},{"id":"6","name":"Electrical"},{"id":"7","name":"Flooring"},{"id":"8","name":"Heating Repair"},{"id":"9","name":"Landscaping"},{"id":"10","name":"Plumbing"},{"id":"11","name":"Remodeling\/Renovation"},{"id":"12","name":"Window Coverings"}]}