java - Android SQLite，如何将Cursor变成字符串？

Question

假设我有这样的 helper :

public class SqlHelper extends SQLiteOpenHelper {

    public SqlHelper(Context context, String name, CursorFactory factory, int version) {
        super(context, name, factory, version);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL("CREATE TABLE MyTable (ID INTEGER PRIMARY KEY, NAME TEXT, PLACE TEXT)");
        db.execSQL("INSERT INTO MyTable (NAME, PLACE) VALUES('ANTHONY','USA')");
        db.execSQL("INSERT INTO MyTable (NAME, PLACE) VALUES('BERIMOR','UK')");
        db.execSQL("INSERT INTO MyTable (NAME, PLACE) VALUES('IVAN','RUSSIA')");
    }


    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
    }


}

在我的主代码中我执行一个查询

    SqlHelper sqlHelper = new SqlHelper(this, "MyDataBase.db", null, 1);
    SQLiteDatabase DB = sqlHelper.getReadableDatabase();

    Cursor c = DB.query(
            "MyTable" /* table */,
            new String[] { "PLACE" } /* columns */,
            "id = ?" /* where or selection */,
            new String[] { "RUSSIA" } /* selectionArgs */,
            null /* groupBy */,
            null /* having */,
            null /* orderBy */
        );

    DB.close();

但我不确定那个光标是什么？难道不应该是一个数组之类的东西吗？如果是这样，我如何从中获取原始值(字符串)？像这样的查询应该返回“IVAN”。

谢谢!

编辑2:

这个( c.getCount() )仍然返回 0，即没有结果...嗯...也许那么助手有问题？

     Cursor c = DB.query(
                "MyTable" /* table */,
                new String[] { "NAME" } /* columns */,
                "PLACE = 'RUSSIA'" /* where or selection */,
                null /* selectionArgs */,
                null /* groupBy */,
                null /* having */,
                null /* orderBy */
            );



    Log.e("DB RETURNS", String.valueOf( c.getCount() ) );

Answer 1

The Cursor object returned by a query provides access to a recordset of results.

获得游标后，您必须迭代它才能获取值。在你的情况下，你会这样做——

if (cur.moveToFirst()) {
    int placeColumn = cur.getColumnIndex("PLACE"); 
    String place = cur.getString(placeColumn);
}

要根据 PLACE 的查询获取 NAME，您应该执行 PLACE = ?

 Cursor c = DB.query(
            "MyTable" /* table */,
            new String[] { "NAME" } /* columns */,
            "PLACE = ?" /* where or selection */,
            new String[] { "RUSSIA" } /* selectionArgs */,
            null /* groupBy */,
            null /* having */,
            null /* orderBy */
        );