Question

这是错误日志：

03-13 10:00:15.778: W/System.err(2558): org.json.JSONException: No value for objects
03-13 10:00:15.778: W/System.err(2558):     at org.json.JSONObject.get(JSONObject.java:354)
03-13 10:00:15.778: W/System.err(2558):     at org.json.JSONObject.getJSONArray(JSONObject.java:544)
03-13 10:00:15.778: W/System.err(2558):     at com.app.Main$ListTask.doInBackground(Main.java:104)
03-13 10:00:15.778: W/System.err(2558):     at com.app.Main$ListTask.doInBackground(Main.java:1)
03-13 10:00:15.778: W/System.err(2558):     at android.os.AsyncTask$2.call(AsyncTask.java:287)
03-13 10:00:15.778: W/System.err(2558):     at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
03-13 10:00:15.778: W/System.err(2558):     at java.util.concurrent.FutureTask.run(FutureTask.java:137)
03-13 10:00:15.778: W/System.err(2558):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
03-13 10:00:15.778: W/System.err(2558):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
03-13 10:00:15.778: W/System.err(2558):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
03-13 10:00:15.778: W/System.err(2558):     at java.lang.Thread.run(Thread.java:856)

活动代码

package com.app;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;

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.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.util.Log;
import android.view.Menu;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class Main extends Activity {

    ListView List;
    ArrayList<String> listArray = new ArrayList<String>();
    ArrayAdapter<String> Adapter;
    Context context;
    String url = "http://sandzak.today/api/1/categories/?format=json/api/projekti/10?=";

    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        context = this;
        List = (ListView) findViewById(R.id.lista);
        Adapter = new ArrayAdapter<String>(this, R.layout.lista, listArray);
        List.setAdapter(Adapter);

        VideoListTask loaderTask = new VideoListTask();
        loaderTask.execute();

    }

    @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;
    }

    public class VideoListTask extends AsyncTask<Void, Void, Void>{

        ProgressDialog dialog;
        @Override
        protected void onPreExecute() 
        {
            dialog = new ProgressDialog(context);
            dialog.setTitle("Loading Category");
            dialog.show();
            super.onPreExecute();
        }

        @Override
        protected Void doInBackground(Void... params) 
        {
            HttpClient client = new DefaultHttpClient();
            HttpGet getRequest = new HttpGet(url);

            try 
            {
                HttpResponse responce = client.execute(getRequest);
                StatusLine statusLine = responce.getStatusLine();
                int statusCode = statusLine.getStatusCode();

                if(statusCode != 200)
                {
                    return null;
                }

                InputStream jsonStream = responce.getEntity().getContent();
                BufferedReader reader = new BufferedReader(new InputStreamReader(jsonStream));
                StringBuilder builder = new StringBuilder();
                String line;
                while((line = reader.readLine())!=null)
                {
                    builder.append(line);
                }



                String jsonData = builder.toString();

                JSONObject json = new JSONObject(jsonData);
                JSONObject meta = json.getJSONObject("meta");
                JSONArray objects = meta.getJSONArray("objects");

                for(int i =0; i<objects.length(); i++)
                {
                    JSONObject video = objects.getJSONObject(i);
                    listArray.add(video.getString("name"));
                }


            }
            catch (ClientProtocolException e)
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } 
            catch (IOException e) 
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            catch (JSONException e) 
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            dialog.dismiss();
            Adapter.notifyDataSetChanged();
            super.onPostExecute(result);
        }
    }
}

我该如何解决这个问题？

Answer 1

在此节点上指出要附加字符串，然后将其传递给对象。在对象中，您需要传递字符串，这是json的关键术语。

while((line = reader.readLine())!=null)
                {
                    builder.append(line);
                }

Answer 2

将inputstrem转换为字符串是一种简单的方法： InputStream inputStream = url.openStream(); Scanner in = new Scanner(inputStream).useDelimiter("\\A"); String str = in.hasNext() ? in.next() : null;
更喜欢使用JSONObject.optXxx(field)而不是JSONObject.getXxx(field)，这是你不喜欢的。需要担心json数据中的字段是否可以转换为您想要的类型。此外，如果字段不是JSONObject.optXxx(field, fallback)，则JSONObject.getXxx()具有后备值。 t存在或不能转换为特定类型。
（可选）如果您想使用JSONObject.has(fieldname)，可以先使用{{1}}

希望它＆＃39;很有用。

Answer 3

最好在调用服务时使用responsehandler。

ResponseHandler<String> responseHandler = new BasicResponseHandler();
final String responseBody = httpclient.execute(httppost, responseHandler);

它会直接给我回复字符串。

如何解决Android应用程序的JSON错误？

3 个答案: