android：在listView中显示搜索结果时，应用程序已关闭

当我的应用程序尝试显示搜索结果时，应用程序关闭如下：

这是logcat中显示的信息

E/缓冲区错误（784）：转换结果java.lang.NullPointerException:lock==null时出错

E/JSON解析器（784）：解析数据org.JSON.JSONException时出错：输入结束于的字符0处

W/dalvikvm（784）：线程ID=15：线程退出时出现未捕获异常（组=0x40a71930）

E/AndroidRuntime（784）：致命异常：异步任务4

E/AndroidRuntime（784）：java.lang.RuntimeException:执行doInBackground（）时出错

E/AndroidRuntime（784）：位于android.os.AsyncTask$3.done（AsyncTask.java:299）

E/AndroidRuntime（784）：位于java.util.concurrent.FutureTask.finishCompletion（FutureTask.java:352）

E/AndroidRuntime（784）：在 java.util.concurrent.FutureTask.setException（FutureTask.java:219）

E/AndroidRuntime（784）：在 java.util.concurrent.FutureTask.run（FutureTask.java:239）

E/AndroidRuntime（784）：位于android.os.AsyncTask$SerialExecutor$1.run（AsyncTask.java:230）

E/AndroidRuntime（784）：位于java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1080）

E/AndroidRuntime（784）：位于java.util.concurrent.ThreadPoolExecutor$Worker.run（ThreadPoolExecutor.java:573）

E/AndroidRuntime（784）：位于java.lang.Thread.run（Thread.java:856）

E/AndroidRuntime（784）：由以下原因引起：java.lang.NullPointerException

E/AndroidRuntime（784）：在com.example.qrandrary.SearchResultDisplay$LoadAllBooks.doInBackground（SearchResultDisplay.java:82）

E/AndroidRuntime（784）：在com.example.qrandrary.SearchResultDisplay$LoadAllBooks.doInBackground（SearchResultDisplay.java:1）

E/AndroidRuntime（784）：位于android.os.AsyncTask$2.call（AsyncTask.java:287）

E/AndroidRuntime（784）：位于java.util.concurrent.FutureTask.run（FutureTask.java:234）

E/AndroidRuntime（784）：。。。4更多 11-23 14:24:49.267:W/EGL_仿真（784）：未实现eglSurfaceAttrib

E/WindowManager（784）：Activity com.example.qrandrary.SearchResultDisplay泄漏了最初添加到此处的window com.android.internal.policy.impl.PhoneWindow$DecorView{40dec338 V.E…..R…D 0,0-470144}

E/WindowManager（784）：android.view.WindowLeaked:Activity com.example.qrandrary.SearchResultDisplay泄漏了最初添加到此处的window com.android.internal.policy.impl.PhoneWindow$DecorView{40dec338 V.E…..R….D 0,0-470144}

E/WindowManager（784）：位于android.view.ViewRootImpl（ViewRootImpl.java:354）

E/WindowManager（784）：位于android.view.WindowManagerGlobal.addView（WindowManagerGlobal.java:216）

E/WindowManager（784）：在android.view.WindowManagerImpl.addView（WindowManagerImpl.java:69）

E/WindowManager（784）：位于android.app.Dialog.show（Dialog.java:281）

E/WindowManager（784）：位于com.example.qrandrary.SearchResultDisplay$LoadAllBooks.onPreExecute（SearchResultDisplay.java:68）

E/WindowManager（784）：位于android.os.AsyncTask.executeOnExecutor（AsyncTask.java:586）

E/WindowManager（784）：位于android.os.AsyncTask.execute（AsyncTask.java:534）

E/WindowManager（784）：位于com.example.qrandrary.SearchResultDisplay.onCreate（SearchResultDisplay.java:53）

E/WindowManager（784）：位于android.app.Activity.performCreate（Activity.java:5104）

E/WindowManager（784）：位于android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1080）

E/WindowManager（784）：位于android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2144）

E/WindowManager（784）：位于android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2230）

E/WindowManager（784）：在android.app.ActivityThread.access$600（ActivityThread.java:141）

E/WindowManager（784）：位于android.app.ActivityThread$H.handleMessage（ActivityThread.java:1234）

E/WindowManager（784）：位于android.os.Handler.dispatchMessage（Handler.java:99）

E/WindowManager（784）：位于android.os.Looper.loop（Looper.java:137）

E/WindowManager（784）：在 ndroid.app.ActivityThread.main（ActivityThread.java:5041）

E/WindowManager（784）：位于java.lang.reflect.Method.Invokenactive（本机方法）

E/WindowManager（784）：位于java.lang.reflect.Method.invoke（Method.java:511）

E/WindowManager（784）：位于com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:793）

E/WindowManager（784）：位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:560）

E/WindowManager（784）：位于dalvik.system.NativeStart.main（本机方法）

代码如下：

public class SearchResultDisplay extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();

ArrayList<HashMap<String, String>> booksList;

// url to get all products list
private static String url_all_books = "http://127.0.0.1/qrandrary/quickSearch.php";

// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_BOOKS = "books";
private static final String TAG_BID = "bid";
private static final String TAG_BNAME = "bname";
private static final String TAG_AUTHORS = "authors";
private static final String TAG_STATUS = "status";
private static final String TAG_PUBLISHER = "publisher";
ListView listView;
List<RowItem> rowItems;
// products JSONArray
JSONArray books = null;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.search_resultlist_view);
    rowItems = new ArrayList<RowItem>();
    listView = (ListView) findViewById(android.R.id.list);
    new LoadAllBooks().execute();
}

class LoadAllBooks extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(SearchResultDisplay.this);
        pDialog.setMessage("Loading Books. Please wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }

    protected String doInBackground(String... args) {
        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        // getting JSON string from URL
        Bundle extras = getIntent().getExtras();
        String keyword = extras.getString("keyword");
        url_all_books = url_all_books + "?keyword=" + keyword;
        JSONObject json = jParser.makeHttpRequest(url_all_books, "GET",
                params);

        // Check your log cat for JSON reponse
        Log.d("All Books: ", json.toString());

        try {
            // Checking for SUCCESS TAG
            int success = json.getInt(TAG_SUCCESS);

            if (success == 1) {
                // products found
                // Getting Array of Products
                books = json.getJSONArray(TAG_BOOKS);

                // looping through All Products
                for (int i = 0; i < books.length(); i++) {
                    JSONObject c = books.getJSONObject(i);

                    // Storing each json item in variable
                    String bid = c.getString(TAG_BID);
                    String bName = c.getString(TAG_BNAME);
                    String authors = c.getString(TAG_AUTHORS);
                    String publisher = c.getString(TAG_PUBLISHER);
                    String status = c.getString(TAG_STATUS);
                    // creating new HashMap
                    HashMap<String, String> map = new HashMap<String, String>();

                    // adding each child node to HashMap key => value
                    map.put(TAG_BID, bid);
                    map.put(TAG_BNAME, bName);
                    map.put(TAG_AUTHORS, authors);
                    map.put(TAG_PUBLISHER, publisher);
                    map.put(TAG_STATUS, status);

                    // adding HashList to ArrayList
                    booksList.add(map);
                }
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }

    protected void onPostExecute(String file_url) {
        // dismiss the dialog after getting all products
        pDialog.dismiss();
        // updating UI from Background Thread
        runOnUiThread(new Runnable() {
            public void run() {
                /**
                 * Updating parsed JSON data into ListView
                 * */
                BookListViewAdapter adapter = new BookListViewAdapter(SearchResultDisplay.this,R.layout.search_result_item, rowItems);
                listView.setAdapter(adapter);
            }
        });

    }
}
}

public class BookListViewAdapter extends ArrayAdapter<RowItem> {

    Context context;

    public BookListViewAdapter(Context context, int resourceId,
            List<RowItem> items) {
        super(context, resourceId, items);
        this.context = context;
    }


    /*private view holder class*/
    private class ViewHolder {
        TextView txtBid;
        TextView txtBname;
        TextView txtAuthors;
        TextView txtPublisher;
        TextView txtStatus;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        RowItem rowItem = getItem(position);

        LayoutInflater mInflater = (LayoutInflater) context
                .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.search_result_item, null);
            holder = new ViewHolder();
            holder.txtBid = (TextView) convertView.findViewById(R.id.bid);
            holder.txtBname = (TextView) convertView.findViewById(R.id.bName);
            holder.txtAuthors = (TextView) convertView.findViewById(R.id.authors);
            holder.txtPublisher = (TextView) convertView.findViewById(R.id.publisher);
            holder.txtStatus = (TextView) convertView.findViewById(R.id.status);
            convertView.setTag(holder);
        } else
            holder = (ViewHolder) convertView.getTag();

        holder.txtBid.setText(rowItem.getbId());
        holder.txtBname.setText(rowItem.getbName());
        holder.txtAuthors.setText(rowItem.getAuthors());
        holder.txtPublisher.setText(rowItem.getPublisher());
        holder.txtStatus.setText(rowItem.getStatus());

        return convertView;
    }
}
public class RowItem {
    private int bId;
    private String bName;
    private String authors;
    private String status;
    private String publisher;
    public RowItem(int bId, String bName, String authors, String status,
            String publisher) {
        this.bId = bId;
        this.bName = bName;
        this.authors = authors;
        this.status = status;
        this.publisher = publisher;
    }
    public int getbId() {
        return bId;
    }
    public void setbId(int bId) {
        this.bId = bId;
    }
    public String getbName() {
        return bName;
    }
    public void setbName(String bName) {
        this.bName = bName;
    }
    public String getAuthors() {
        return authors;
    }
    public void setAuthors(String authors) {
        this.authors = authors;
    }
    public String getStatus() {
        return status;
    }
    public void setStatus(String status) {
        this.status = status;
    }
    public String getPublisher() {
        return publisher;
    }
    public void setPublisher(String publisher) {
        this.publisher = publisher;
    }



}

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    // function get json from url
    // by making HTTP POST or GET mehtod
    public JSONObject makeHttpRequest(String url, String method,
            List<NameValuePair> params) {

        // Making HTTP request
        try {

            // check for request method
            if(method == "POST"){
                // request method is POST
                // defaultHttpClient
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);
                httpPost.setEntity(new UrlEncodedFormEntity(params));

                HttpResponse httpResponse = httpClient.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();

            }else if(method == "GET"){
                // request method is GET
                DefaultHttpClient httpClient = new DefaultHttpClient();
                String paramString = URLEncodedUtils.format(params, "utf-8");
                url += "?" + paramString;
                HttpGet httpGet = new HttpGet(url);

                HttpResponse httpResponse = httpClient.execute(httpGet);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();
            }           

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        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();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

公共类SearchResultDisplay扩展了ListActivity{
//进度对话框
私人对话；
//创建JSON解析器对象
JSONParser jParser=新的JSONParser（）；
ArrayList图书列表；
//获取所有产品列表的url
私有静态字符串url\u所有\u书籍=”http://127.0.0.1/qrandrary/quickSearch.php";
//JSON节点名称
私有静态最终字符串标记_SUCCESS=“SUCCESS”；
私有静态最终字符串标记_BOOKS=“BOOKS”；
私有静态最终字符串标记_BID=“BID”；
私有静态最终字符串标记_BNAME=“BNAME”；
私有静态最终字符串标记_AUTHORS=“AUTHORS”；
私有静态最终字符串标记_STATUS=“STATUS”；
私有静态最终字符串标记\u PUBLISHER=“PUBLISHER”；
列表视图列表视图；
列出项目；
//产品JSONArray
JSONArray books=null；
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.search\u resultlist\u视图）；
rowItems=新的ArrayList（）；
listView=（listView）findViewById（android.R.id.list）；
新建LoadAllBooks（）.exe