android - 无法从动态创建的 sqlite 表'列中检索单个字符串数据并导致 "Index 0 requested, with a size of 0"

Question

但是当动态创建的表和选择查询在同一方法中时，我可以检索字符串数据。

动态创建Table helper.classhomework(tablename,dateString);

public void classhomework(String tablename,String date){

    String COLUMN_ID="S.No";

    String COLUMN_SUBJECT1="subject1"; 

    String COLUMN_SUBJECT2="subject2";

    String COLUMN_SUBJECT3="subject3";

    String COLUMN_dATE="date";

    ContentValues insertValues = new ContentValues();
    SQLiteDatabase db = getWritableDatabase();
    db.execSQL("CREATE TABLE IF NOT EXISTS "+ tablename+ "( " +
        COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
        COLUMN_SUBJECT1 + " TEXT, " +
        COLUMN_SUBJECT2 + " TEXT, " +
        COLUMN_SUBJECT3 + " TEXT, " +
        COLUMN_dATE     + " TEXT " +
        ");");
    insertValues.put(COLUMN_SUBJECT1,"Not updated ");
    insertValues.put(COLUMN_SUBJECT2,"Not updated ");
    insertValues.put(COLUMN_SUBJECT3,"Not updated ");
    insertValues.put(COLUMN_dATE,date);

    db.insert(tablename,null,insertValues);
    db.close();
}

调用选择查询方法

String homeworkdetails=helper.gethomework(dateString,tablename,subjtxt);

选择查询方式

    public String gethomework(String date,String tablename,String subject){

    String COLUMN_dATE="date";

    SQLiteDatabase db = getWritableDatabase();

    String homeworkcontent = null;
    Cursor cur=db.query(tablename,new String[]{subject},COLUMN_dATE+"=?",new                               String[]{String.valueOf(date)},null,null,null,null);
    if(cur!=null){
        cur.moveToFirst();
  homeworkcontent =cur.getString(0);//**CursorIndexOutOfBoundsException**
    }cur.close();
        db.close();
    return homeworkcontent;

但在该方法内创建表时返回值。

调用更新查询

helper.updatehomework(dateString,homeworksubmt,subjectname,tabname)

更新查询

    public boolean updatehomework(String date,String homework,String subject,String table ){
        try{ContentValues updateValues = new ContentValues();
        SQLiteDatabase db = getWritableDatabase();
        updateValues.put(subject,homework);
        db.update(table,updateValues,"date =?",new String[]{date});
         return true;

        }catch (Exception me){
            me.printStackTrace();
        }return false;
    }

值已成功更新。

验证了所有表名称的用法。

Answer 1

出现此错误是因为您的光标没有行。您必须检查尺寸条件。

if(cur!=null  && cur..getCount() > 0)
{
......
}