无法将 JSON 解析为 ListView

Question

我正在尝试

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我想深入了解 JSON。为此，我为我的 Youtube 频道创建了一个应用程序。首先，我在此网站上创建了我的频道的 JSON 文件：GData Youtube 和创建了此 JSON 文件：频道的 JSON< /a>.

之后，我开始使用本教程创建我的频道应用程序： JSON 教程，我对其进行了一些更改，它“应该”与我的 Channel-JSON-File 一起使用，但它就是不起作用，我真的不明白为什么，这是我总是出现的错误消息 得到。 11-22 08:35:37.932: E/CANT READ DATA(15923): 解析数据时出错 org.json.JSONException: java.lang.String 类型的值响应无法转换为 JSONObject

是 JSONfunction.java 的代码适用于教程，但这里不是，所以 main.java 中一定有问题，但我不明白什么是错误的。！！！ :(

问题

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我需要在 Main.java 中更改什么才能使我的代码正常工作。如果您有针对我遇到的问题的教程，或者非常好的代码示例，我也会很高兴。 频道中的 JSON 文件如下所示： JSON-结构 您可以在此处找到代码和错误日志：

代码

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JSONfunction.java

package de.stepforward;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
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 JSONfunction {

    public static JSONObject getJSONfromURL(String url){
        InputStream is = null;
        String result = "";
        JSONObject jArray = null;

        //http post
        try{
                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost(url);
                HttpResponse response = httpclient.execute(httppost);
                HttpEntity entity = response.getEntity();
                is = entity.getContent();

        }catch(Exception e){
                Log.e("NO CONNECTION", "Error in http connection "+e.toString());
        }

      //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){
                Log.e("CANT CONVERT DATA", "Error converting result "+e.toString());
        }

        try{

            jArray = new JSONObject(result);            
        }catch(JSONException e){
                Log.e("CANT READ DATA", "Error parsing data "+e.toString());
        }

        return jArray;
    }
}

ShowChannel.java

    package de.stepforward;

import java.util.ArrayList;
import java.util.HashMap;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.ListActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;


public class ShowChannel  extends ListActivity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();

        JSONObject json = JSONfunction.getJSONfromURL("http://gdata.youtube.com/feeds/mobile/users/TheStepForward/uploads?alt=json&format=1");

        try{
        JSONObject feed = json.getJSONObject("feed");   
        JSONArray entry = feed.getJSONArray("entry");

        for(int i=0;i<entry.length();i++){                      
            HashMap<String, String> map = new HashMap<String, String>();    
            JSONObject e = entry.getJSONObject(i);

            map.put("title", e.getString("title.$t"));
            map.put("description", e.getString("content.$t"));
            map.put("link", e.getString("media$player"));
            map.put("thumbnail", e.getString("media$thumbnail.url"));
            mylist.add(map);

        }



        }catch(JSONException e)        {
         Log.e("log_tag", "Error parsing data "+e.toString());
       }

        //Liste füllen
        ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.listlayout, 
                new String[] {"thumbnail", "title", "description", "link" }, 
                new int[] { R.id.img_video, R.id.txt_title, R.id.txt_subtitle });

        setListAdapter(adapter);

        //OnItemClickListner für Hyperlinks
        final ListView lv = getListView();
        lv.setTextFilterEnabled(true);  
        lv.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {   
                @SuppressWarnings("unchecked")
                HashMap<String, String> o = (HashMap<String, String>) lv.getItemAtPosition(position);
                Toast.makeText(ShowChannel.this, "Link '" + o.get("link") + "' was clicked.", Toast.LENGTH_SHORT).show();
            }

        });

    }

}

错误日志

11-22 08:35:37.932: E/CANT READ DATA(15923): Error parsing data org.json.JSONException: Value Response of type java.lang.String cannot be converted to JSONObject
11-22 08:35:37.932: D/AndroidRuntime(15923): Shutting down VM
11-22 08:35:37.932: W/dalvikvm(15923): threadid=1: thread exiting with uncaught exception (group=0x4001d5a0)
11-22 08:35:38.032: E/AndroidRuntime(15923): FATAL EXCEPTION: main
11-22 08:35:38.032: E/AndroidRuntime(15923): java.lang.RuntimeException: Unable to start activity ComponentInfo{de.stepforward/de.stepforward.ShowChannel}: java.lang.NullPointerException
11-22 08:35:38.032: E/AndroidRuntime(15923):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1816)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1837)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at android.app.ActivityThread.access$1500(ActivityThread.java:132)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1033)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at android.os.Looper.loop(Looper.java:143)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at android.app.ActivityThread.main(ActivityThread.java:4196)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at java.lang.reflect.Method.invokeNative(Native Method)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at java.lang.reflect.Method.invoke(Method.java:507)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at dalvik.system.NativeStart.main(Native Method)
11-22 08:35:38.032: E/AndroidRuntime(15923): Caused by: java.lang.NullPointerException
11-22 08:35:38.032: E/AndroidRuntime(15923):    at de.stepforward.ShowChannel.onCreate(ShowChannel.java:36)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
11-22 08:35:38.032: E/AndroidRuntime(15923):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1780)
11-22 08:35:38.032: E/AndroidRuntime(15923):    ... 11 more

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感谢您提前提供帮助 最好的问候 游猎

Answer 1

为了强调 user370305 的观点（作为单独的答案发布，因为注释中的多行代码不容易阅读）：

// No good.
String notJsonObject = "This is not a JSON object.";
JSONObject jsonObject = new JSONObject(notJsonObject);

// Good.
String validJsonObject = "{\"foo\":\"bar\"}";
JSONObject jsonObject = new JSONObject(validJsonObject);