Sqlite:如何将行值增加+1?
我有一个TOTALCOUNT表,它有一个PK _id列和一个整数列CARDNUM。我想将CARDNUM的默认值设置为零。然后,每次将新行插入数据库时,将CARDNUM增加+1。因此,5行插入将为行ID 1到5生成1,2,3,4,5。当我将数据推送到我的RecyclerView中的各个CardView时,我只得到默认值零。前五个CardView应显示CARDNUM值,因此为1,2,3,4,5。我错过了什么 数据库合同文件:Sqlite:如何将行值增加+1?,sqlite,android-cursor,content-values,Sqlite,Android Cursor,Content Values,我有一个TOTALCOUNT表,它有一个PK _id列和一个整数列CARDNUM。我想将CARDNUM的默认值设置为零。然后,每次将新行插入数据库时,将CARDNUM增加+1。因此,5行插入将为行ID 1到5生成1,2,3,4,5。当我将数据推送到我的RecyclerView中的各个CardView时,我只得到默认值零。前五个CardView应显示CARDNUM值,因此为1,2,3,4,5。我错过了什么 数据库合同文件: ... public static final String TABLE_
...
public static final String TABLE_NAME_TOTALCOUNT = "totalcount";
public static final String COLUMN_NAME_COUNTID = "_id";
public static final String COLUMN_NAME_CARDNUM = "cardnum";
}
}
A second table, not shown is called USERINPUTS.
DBHelper文件:
...
public void onCreate(SQLiteDatabase db) {
// Set up the Column headings for USERINPUTS and TOTALCOUNT Tables.
db.execSQL(SQL_CREATE_ENTRIES);
db.execSQL(SQL_CREATE_CARDNUM);
private static final String SQL_CREATE_CARDNUM =
"CREATE TABLE IF NOT EXISTS "+ DBContract.DBEntry.TABLE_NAME_TOTALCOUNT +
"( "+ DBContract.DBEntry.COLUMN_NAME_COUNTID +
" INTEGER PRIMARY KEY , "+
DBContract.DBEntry.COLUMN_NAME_CARDNUM +
" INTEGER);";
public void insertIntoTableTOTALCOUNT() {
SQLiteDatabase db = this.getWritableDatabase();
db.beginTransaction();
String select = "Select * from "+ DBContract.DBEntry.TABLE_NAME_TOTALCOUNT;
Cursor c =db.rawQuery(select, null);
int cardnum=0;
try {
if (c.moveToFirst()) {
cardnum = c.getInt(1);
cardnum++;
}
} finally {
if(c !=null && !c.isClosed()){
c.close();
}
}
ContentValues cv = new ContentValues();
cv.put(DBContract.DBEntry.COLUMN_NAME_CARDNUM,cardnum);
db.insert(DBContract.DBEntry.TABLE_NAME_TOTALCOUNT,null,cv);
db.setTransactionSuccessful();
db.endTransaction();
// Close the database.
if(db.isOpen())
db.close();
}
...
// Two Tables push the data to a RecyclerView list.
public List<UserData> getDataFromDB(){
List<UserData> modelList = new ArrayList<>();
String query = "SELECT *, (SELECT " + DBContract.DBEntry.COLUMN_NAME_CARDNUM +
" from " + DBContract.DBEntry.TABLE_NAME_TOTALCOUNT +") from "
+ DBContract.DBEntry.TABLE_NAME_USERINPUTS +";";
SQLiteDatabase db = this.getReadableDatabase();
db.beginTransaction();
Cursor cursor = db.rawQuery(query, null);
Log.d("TAG", DatabaseUtils.dumpCursorToString(cursor));
try {
if (cursor.moveToFirst()) {
do {
UserData userData = new UserData();
userData.setTodo(cursor.getString(1));
userData.setNote1(cursor.getString(2));
userData.setNote2(cursor.getString(3));
userData.setDuedate(cursor.getString(4));
userData.setDuetime(cursor.getString(5));
userData.setTimestamp(cursor.getLong(6));
userData.setCardnum(cursor.getInt(7));
modelList.add(0, userData);
} while (cursor.moveToNext());
}
} finally {
if(cursor !=null && !cursor.isClosed()){
cursor.close();
}
}
db.setTransactionSuccessful();
db.endTransaction();
return modelList;
}
通过在创建表时添加AUTOINCREMENT选项,您可以很容易地做到这一点,它将自动递增 或者顺便说一句,但在处理游标时,您丢失了 这样试试
Android Studio警告说状况c!=null始终为true。它将始终为true,直到最后一行具有表的值,然后moveToNext方法将返回null cursorApp崩溃。使用我上面的方法,错误消息显示CursorIndexOutOfBoundsException:请求索引0,行cardnum=c.getInt1的大小为0;有一个不自动递增的主键值有什么意义?我希望有一列值以+1递增,默认值为0。我是SQLite的新手,所以不确定最好的方法是什么。看一看。谢谢,我会看一看…我很感谢你回来给我更多的建议。我为我的泄气道歉,我不是故意的。我从没想过你真的泄气了。您的设计可能有一些缺陷,但至少现在有两种方法可以自动增加列。
Cursor c =db.rawQuery(select, null);
int cardnum=0;
c.moveToFirst();
while( c != null )
{
cardnum = c.getInt(1);
cardnum++;
c.moveToNext();
}