Question

我正在尝试获取列＆＃34; _id＆＃34;的数据。（这是第一列），名称和密码列（共3列）

但是我收到了此错误消息

无法从CursorWindow读取第0行，第-1列......

所以我运行测试以使用getColumnCount（）获取列数但返回 2

之后我开始获取所有列的索引，我发现＆＃34; _id＆＃34; 列返回值（ - 1），并且＆＃ 39;为什么我收到错误信息

我查看了我的查询语句，但它没有任何问题。

有人能告诉我我的代码有什么问题吗？

    public class SQLiteAdapter {

        SQLiteHelper helper;

        public SQLiteAdapter(Context context) {
            helper = new SQLiteHelper(context);
        }

        public String getAllData() {
            SQLiteDatabase db = helper.getWritableDatabase();

            // select _id, name, password from ahmadssbdb
            String[] columns = { SQLiteHelper.COL_NAME, SQLiteHelper.COL_PASSWORD };

            Cursor cursor = db.query(SQLiteHelper.TABLE_NAME, columns, null, null,
                    null, null, null);

            StringBuffer strBuffer = new StringBuffer();

            int indexUID = cursor.getColumnIndex(SQLiteHelper.COL_ID);
            int indexColName = cursor.getColumnIndex(SQLiteHelper.COL_NAME);
            int indexColPassword = cursor.getColumnIndex(SQLiteHelper.COL_PASSWORD);
            String uid = " " + indexUID + " " + indexColName + " "  + indexColPassword;
            return uid;


        /*************************************
         *  Retrieve  data from each column 
         *************************************/

        /*
         * while(cursor.moveToNext()){
         * 
         * long uid = cursor.getInt(indexUID); 
         * String name = cursor.getString(indexColName);
         * String password = cursor.getString(indexColPassword); 
         * strBuffer.append(uid + " " + name + " " + password + "\n"); }
         * 
         * return strBuffer.toString();
         */
        }

    static class SQLiteHelper extends SQLiteOpenHelper {
        private Context context;

        // Defined Database Schema
        private static final String DATABASE_NAME = "dbname";
        private static final String TABLE_NAME = "db_table";
        private static final int DATABASE_VERSION = 4;
        private static final String COL_ID= "_id";
        private static final String COL_NAME = "name";
        private static final String COL_PASSWORD = "password";

        // List of Queries
        private static final String QUERY_CREATE_TABLE = 
                "CREATE TABLE " + TABLE_NAME + " (" 
                + COL_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " 
                + COL_NAME + " VARCHAR(250), " 
                + COL_PASSWORD + " VARCHAR(250)" +
                ");";

        private static final String QUERY_DROP_TABLE = "DROP TABLE IF EXISTS " + TABLE_NAME;

        public SQLiteHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
            this.context = context;
            Message.message(context, "constructer was called");
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            try {
                // CREATE TABLE ahamadssb_table (_id INTEGER PRIMARY KEY
                // AUTOINCREMENT, name VARCHAR(255));
                db.execSQL(QUERY_CREATE_TABLE);
                Message.message(context, "onCreate was  called");
            } catch (SQLException e) {
                Message.message(context, "" + e);
            }

        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            try {
                db.execSQL(QUERY_DROP_TABLE);
                onCreate(db);
                Message.message(context, "onUpgrade  was called");
            } catch (SQLException e) {
                Message.message(context, "" + e);
            }

        }

    }
}

Answer 1

您的查询没有要求id列。将它添加到您的columns变量：

String[] columns = { SQLiteHelper.COL_ID, SQLiteHelper.COL_NAME, SQLiteHelper.COL_PASSWORD };

Answer 2

你必须添加＆＃34; _id＆＃34;列到投影数组。它在投影中不存在，因此getColumnIndex返回-1

http://developer.android.com/reference/android/database/Cursor.html#getColumnIndex(java.lang.String)

第一列索引（_id）= -1

2 个答案: