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我不知道我的代码有什么问题。它应该返回视频标题列表，但强制关闭。我究竟做错了什么？

代码（请原谅基本评论）。

package com.aer.illbehonest;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;

import org.apache.commons.io.IOUtils;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class VideosList extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_videos_list);

        new GetTitlesTask().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.activity_videos_list, menu);
        return true;
    }

    class GetTitlesTask extends AsyncTask<String, Void, ArrayList<String>> {

        ArrayList<String> titlesList;

    @Override
    protected ArrayList<String> doInBackground(String... args) {

            URL jsonURL = null;
            try {
                jsonURL = new URL("http://gdata.youtube.com/feeds/api/users/illbehonest/uploads?v=2&alt=jsonc");
            } catch (MalformedURLException e) {
                System.out.println("Malformed URL... check");
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
                URLConnection jc = null;
                try {
                    jc = jsonURL.openConnection();
                } catch (IOException e) {
                    System.out.println("jc problem");
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                InputStream is = null;
                try {
                    is = jc.getInputStream();
                } catch (IOException e) {
                    System.out.println("is problem");
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                String jsonTxt = null;
                try {
                    jsonTxt = IOUtils.toString(is);
                } catch (IOException e) {
                    System.out.println("jsontxt problem");
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

            JsonObject json = new JsonParser().parse(jsonTxt).getAsJsonObject();
            JsonObject jdata = json.getAsJsonObject("data");
            JsonArray jentry = jdata.getAsJsonArray("items");

            for (int entryNumber = 0; entryNumber<=25; entryNumber++){

                JsonObject entry = jentry.get(entryNumber).getAsJsonObject();
                titlesList.add(entry.get("title").toString());

                }

            return titlesList;
        }
        protected void onPostExecute(ArrayList<String> result) {
            ListView listView = (ListView)VideosList.this.findViewById(R.id.videolist);
            ArrayAdapter<String> adapter = new ArrayAdapter<String> (VideosList.this,
                    android.R.layout.simple_list_item_1, android.R.id.text1, titlesList);
            (listView).setAdapter(adapter);
        }

    }
}

这是我的 LogCat 输出（注意我使用的是远程物理设备）。

01-21 01:19:11.430: W/dalvikvm(389): threadid=11: thread exiting with uncaught exception (group=0x41b28930)
01-21 01:19:11.696: E/AndroidRuntime(389): FATAL EXCEPTION: AsyncTask #1
01-21 01:19:11.696: E/AndroidRuntime(389): java.lang.RuntimeException: An error occured while executing doInBackground()
01-21 01:19:11.696: E/AndroidRuntime(389):  at android.os.AsyncTask$3.done(AsyncTask.java:299)
01-21 01:19:11.696: E/AndroidRuntime(389):  at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
01-21 01:19:11.696: E/AndroidRuntime(389):  at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
01-21 01:19:11.696: E/AndroidRuntime(389):  at java.util.concurrent.FutureTask.run(FutureTask.java:239)
01-21 01:19:11.696: E/AndroidRuntime(389):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
01-21 01:19:11.696: E/AndroidRuntime(389):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
01-21 01:19:11.696: E/AndroidRuntime(389):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
01-21 01:19:11.696: E/AndroidRuntime(389):  at java.lang.Thread.run(Thread.java:856)
01-21 01:19:11.696: E/AndroidRuntime(389): Caused by: java.lang.NullPointerException
01-21 01:19:11.696: E/AndroidRuntime(389):  at com.aer.illbehonest.VideosList$GetTitlesTask.doInBackground(VideosList.java:87)
01-21 01:19:11.696: E/AndroidRuntime(389):  at com.aer.illbehonest.VideosList$GetTitlesTask.doInBackground(VideosList.java:1)
01-21 01:19:11.696: E/AndroidRuntime(389):  at android.os.AsyncTask$2.call(AsyncTask.java:287)
01-21 01:19:11.696: E/AndroidRuntime(389):  at java.util.concurrent.FutureTask.run(FutureTask.java:234)
01-21 01:19:11.696: E/AndroidRuntime(389):  ... 4 more
4

1 回答 1

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从 entryNumber<=25 更改 for 循环增量；到 entryNumber<25; 可以修复它。

在您从服务器收到的 JSON 数据中，只有 25 个项目，从 0 到 24 您试图访问第 26 个项目。

您可能在 for 循环中使用了 entryNumber <= jentry.Length。

于 2013-01-21T08:38:00.080 回答