java - 这个错误有什么解决办法吗？

Question

01-25 23:51:14.507: WARN/System.err(616): android.database.CursorIndexOutOfBoundsException: 请求索引 -1，大小为 2

我有一个使用 SQLite 数据库的 Android 应用程序。但是当它到达 select 语句时它会强制关闭。我有一个用于执行此操作的类文件:

package com.thesis.menubook;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.util.ArrayList;
import java.util.List;

public class DBConnect {

        int id = 0;
        public static final String KEY_ROWID = "_id";
        public static final String KEY_IP = "saved_ip_address";
        private static final String TAG = "DBConnect";

        private static final String DATABASE_NAME = "MenuBook";
        private static final String DATABASE_TABLE_1 = "ipaddress";
       //private static final String DATABASE_TABLE_2 = "menudb";
       //private static final String DATABASE_TABLE_3 = "recipelist";
        private static final int DATABASE_VERSION = 1;

        private static final String DATABASE_CREATE_TABLE_1 =
            "CREATE TABLE ipaddress (_id integer primary key autoincrement, " +
                                 "saved_ip_address text not null " +
                                 "); ";
        private static final String DATABASE_CREATE_TABLE_2 =
            "CREATE TABLE menudb (menu_ID varchar primary key not null, " +
                                 "menu_name longtext, " +
                                 "menu_price double null default, " +
                                 "menu_description longtext, " +
                                 "menu_category text, " +
                                 "menu_status text " +
                                 "); ";
        private static final String DATABASE_CREATE_TABLE_3 =
            "CREATE TABLE recipelist (recipe_ID integer primary key not null autoincrement, " +
                                 "menu_ID varchar null default, " +
                                 "stock_ID varchar null default, " +
                                 "recipe_quantity double null defualt " +
                                 ");" ;

        private final Context context;

        private static DatabaseHelper DBHelper;
        private static SQLiteDatabase db;

        public DBConnect(Context ctx)
        {
            this.context = ctx;
            DBHelper = new DatabaseHelper(context);
        }

        public static class DatabaseHelper extends SQLiteOpenHelper
        {
            DatabaseHelper(Context context)
            {
                super(context, DATABASE_NAME, null, DATABASE_VERSION);
            }

            @Override
            public void onCreate(SQLiteDatabase db)
            {
                db.execSQL(DATABASE_CREATE_TABLE_1);
                db.execSQL(DATABASE_CREATE_TABLE_2);
                db.execSQL(DATABASE_CREATE_TABLE_3);
            }

            @Override
            public void onUpgrade(SQLiteDatabase db, int oldVersion,
                                  int newVersion)
            {
                Log.w(TAG, "Upgrading database from version " + oldVersion
                      + " to "
                      + newVersion + ", which will destroy all old data");
                db.execSQL("DROP TABLE IF EXISTS ipaddress");
                db.execSQL("DROP TABLE IF EXISTS menudb");
                db.execSQL("DROP TABLE IF EXISTS recipelist");
                onCreate(db);
            }

        }

        //---opens the database---
        public DBConnect open() throws SQLException
        {
            db = DBHelper.getWritableDatabase();
            return this;
        }

        //---closes the database---
        public void close()
        {
            DBHelper.close();
        }

        //---insert a title into the database---
        public long insertIPAddress(String ipaddress)
        {
            ContentValues initialValues = new ContentValues();
            initialValues.put(KEY_IP, ipaddress);
            return db.insert(DATABASE_TABLE_1, null, initialValues);
        }

        public String getIP()
        {
            String retrievedIP;

            String query = "SELECT saved_ip_address FROM ipaddress WHERE _id = (SELECT MAX(_id) FROM ipaddress)";
            Cursor cursor = db.rawQuery(query, null);
            retrievedIP= cursor.getString(cursor.getColumnIndex("saved_ip_address"));
            cursor.close();
            return retrievedIP;
        }

        public List<ColumnValue[]> select(final String query)
        {
            List<ColumnValue[]> result = null;
            Cursor cursor = db.rawQuery(query, null);

            if (cursor.moveToFirst())
            {
                result = new ArrayList<ColumnValue[]>();

                do
                {
                    int columns = cursor.getColumnCount();
                    ColumnValue[] cvarray = new ColumnValue[columns];

                    for (int i=0; i<columns; i++)
                    {
                        String key = cursor.getColumnName(i);
                        String value = cursor.getString(i);
                        ColumnValue cv = new ColumnValue(key, value);
                        cvarray[i] = cv;
                    }

                    result.add(cvarray);
                }
                while (cursor.moveToNext());
            }

            cursor.close();

            return result;
        }

        public class ColumnValue
        {
            public String column, value;

            public ColumnValue(String c, String v)
            {
                column = c; value = v;
            }
        }


}

我认为它位于 getID() 子句中，但我看不出它或我的 SELECT 语句有任何问题。我在这里尝试做的是获取位于 ipaddress 表最底部的 saved_ip_address 的值。

这是我的 LogCat，其中错误的开头以粗体显示。

谢谢

01-25 23:51:14.507: WARN/System.err(616): android.database.CursorIndexOutOfBoundsException: 请求索引 -1，大小为 2

01-25 23:51:14.568: WARN/System.err(616):     at android.database.AbstractCursor.checkPosition(AbstractCursor.java:421)
01-25 23:51:14.568: WARN/System.err(616):     at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:117)
01-25 23:51:14.578: WARN/System.err(616):     at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:31)
01-25 23:51:14.590: WARN/System.err(616):     at com.thesis.menubook.DBConnect.getIP(DBConnect.java:113)
01-25 23:51:14.590: WARN/System.err(616):     at com.thesis.menubook.ChooseTable$GetTableDetails$1.run(ChooseTable.java:103)
01-25 23:51:14.622: WARN/System.err(616):     at android.os.Handler.handleCallback(Handler.java:587)
01-25 23:51:14.622: WARN/System.err(616):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 23:51:14.622: WARN/System.err(616):     at android.os.Looper.loop(Looper.java:132)
01-25 23:51:14.648: WARN/System.err(616):     at android.app.ActivityThread.main(ActivityThread.java:4025)
01-25 23:51:14.688: WARN/System.err(616):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 23:51:14.688: WARN/System.err(616):     at java.lang.reflect.Method.invoke(Method.java:491)
01-25 23:51:14.688: WARN/System.err(616):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
01-25 23:51:14.688: WARN/System.err(616):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
01-25 23:51:14.688: WARN/System.err(616):     at dalvik.system.NativeStart.main(Native Method)
01-25 23:51:14.998: DEBUG/AndroidRuntime(616): Shutting down VM
01-25 23:51:15.008: WARN/dalvikvm(616): threadid=1: thread exiting with uncaught exception (group=0x40014760)
01-25 23:51:15.138: ERROR/AndroidRuntime(616): FATAL EXCEPTION: main
01-25 23:51:15.138: ERROR/AndroidRuntime(616): java.lang.IllegalArgumentException: Host name may not be null
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at org.apache.http.HttpHost.<init>(HttpHost.java:83)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at org.apache.http.impl.client.AbstractHttpClient.determineTarget(AbstractHttpClient.java:497)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at com.thesis.menubook.JSONParser.makeHttpRequest(JSONParser.java:62)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at com.thesis.menubook.ChooseTable$GetTableDetails$1.run(ChooseTable.java:119)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at android.os.Handler.handleCallback(Handler.java:587)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at android.os.Looper.loop(Looper.java:132)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at android.app.ActivityThread.main(ActivityThread.java:4025)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at java.lang.reflect.Method.invoke(Method.java:491)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
01-25 23:51:15.138: ERROR/AndroidRuntime(616):     at dalvik.system.NativeStart.main(Native Method)
01-25 23:51:15.328: WARN/ActivityManager(83):   Force finishing activity com.thesis.menubook/.ChooseTable
01-25 23:51:15.958: WARN/ActivityManager(83): Activity pause timeout for ActivityRecord{408b4228 com.thesis.menubook/.ChooseTable}
01-25 23:51:20.048: INFO/Process(616): Sending signal. PID: 616 SIG: 9
01-25 23:51:21.068: INFO/ActivityManager(83): Process com.thesis.menubook (pid 616) has died.
01-25 23:51:21.089: ERROR/InputDispatcher(83): channel '408408d0 com.thesis.menubook/com.thesis.menubook.IPAddress (server)' ~ Consumer closed input channel or an error occurred.  events=0x8
01-25 23:51:21.098: ERROR/InputDispatcher(83): channel '408408d0 com.thesis.menubook/com.thesis.menubook.IPAddress (server)' ~ Channel is unrecoverably broken and will be disposed!
01-25 23:51:21.768: INFO/WindowManager(83): WIN DEATH: Window{408408d0 com.thesis.menubook/com.thesis.menubook.IPAddress paused=false}
01-25 23:51:22.108: INFO/WindowManager(83): WIN DEATH: Window{407b66d8 com.thesis.menubook/com.thesis.menubook.ChooseTable paused=false}
01-25 23:51:22.246: INFO/WindowManager(83): WIN DEATH: Window{4097d668 com.thesis.menubook/com.thesis.menubook.ChooseTable paused=false}
01-25 23:51:22.358: INFO/WindowManager(83): WINDOW DIED Window{408408d0 com.thesis.menubook/com.thesis.menubook.IPAddress paused=false}
01-25 23:51:22.449: ERROR/InputDispatcher(83): Received spurious receive callback for unknown input channel.  fd=188, events=0x8
01-25 23:51:22.449: ERROR/InputDispatcher(83): Received spurious receive callback for unknown input channel.  fd=190, events=0x8
01-25 23:51:23.468: DEBUG/dalvikvm(147): GC_EXPLICIT freed <1K, 4% free 12942K/13383K, paused 285ms+19ms
01-25 23:51:23.858: WARN/InputManagerService(83): Got RemoteException sending setActive(false) notification to pid 616 uid 10004
01-25 23:52:15.278: DEBUG/SntpClient(83): request time failed: java.net.SocketException: Address family not supported by protocol
01-25 23:57:15.589: DEBUG/SntpClient(83): request time failed: java.net.SocketException: Address family not supported by protocol

Answer 1

获得 Cursor 对象后，您需要前进到第一行...

 cursor.moveToFirst();

在从游标中获取之前。您还需要检查光标中是否确实存在任何行。