Question

我正在尝试一个简单的插入和读取操作，但我这样做时会遇到异常。

这是我正在尝试的代码，

try{
    SQLiteDatabase db = openOrCreateDatabase("iTimeDB", MODE_PRIVATE, null);
    db.execSQL("CREATE TABLE IF NOT EXISTS Activities (ID INTEGER PRIMARY KEY AUTOINCREMENT ,IMEI VARCHAR, Title VARCHAR, Time VARCHAR);");
    db.execSQL("INSERT INTO Activities(IMEI, Title, Time) VALUES('"+ IMEI +"','"+ title +"','" +time+"');");
    Cursor c = db.rawQuery("SELECT MAX(ID) FROM Activities", null);
    c.moveToFirst();
    String ID = c.getString(c.getColumnIndex("ID"));
    Log.v("column: ID", ID);
    db.close();

    }
    catch(Exception e)
    {
        e.printStackTrace();
        Log.v("YYY", e.toString());
    }

插入数据时没有异常，但是当我尝试从DB读取时，这是异常

这是LogCat

01-02 11:02:46.992: V/YYY(20510): java.lang.IllegalStateException: Couldn't read row
0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before
accessing data from it.

Answer 1

试试这种方式

String ID = c.getInt(0);

OR

Cursor c = db.rawQuery("SELECT MAX(ID)'ID' FROM Activities", null);
    c.moveToFirst();
    String ID = c.getString(c.getColumnIndex("ID"));

Answer 2

这可能是因为您的查询和光标过滤器

您的查询

Cursor c = db.rawQuery("SELECT MAX(ID) FROM Activities", null);

尝试

Cursor c = db.rawQuery("SELECT MAX(ID) as newID FROM Activities", null);

而不是String ID = c.getString(c.getColumnIndex("ID"));使用String ID = c.getInt(c.getColumnIndex("maxID"));

Answer 3

你应该总是检查游标是否能够使用api moveToFirst（）来获取行。

if(c.moveToFirst())
{
 String ID = c.getString(c.getColumnIndex("ID"));
 Log.v("column: ID", ID);
}
 db.close();

Sqlite Cursor无法从数据库中获取数据

3 个答案: