Building the Right Environment to Support AI, Machine Learning and Deep Learning
This article describes a custom a list box with columns. I will explain how the program works, but for a better understanding you should read the source code. This source is part of a big project that has to do with pizzas and that's why it contains the pizza word in several places.
- In the OnInitDialog() function I am initializing the ClientsLB,
which is of type CDBListBox. I am getting the positions of some
dialog controls and I am using this information to position my
list box at the correct place. The actual initialization of the
ClientsLB is done by calling:
ClientsLB.Init( 20, tmpRect2, this, IDC_CLIENTLB );The first parameter is the height of the list box items
The second its position
The third the parent window
The last is the controls id
Then I am adding tab stops to the control, meaning that I am telling the control where to put each column. This is done by calling
SetTabStop( short ColumnIndex, short ColumnPosition )
In this application I am using the position of the edit controls above my list box in order to set the tabs position.
- The control is now ready to accept data. This is done by calling the
CListBox::AddString() but the string must have a special format. It
contains all the columns seperated by #. For example:
AddString( "column1#column2#column3" )
The control has a function called GetCurrentID(). This function returns the first column of the selected item as a CString, it is assumed that this is an id column. If there is no current selection in the list box, it returns "NS".
It also has a function called ExtractString(). You must call this function twice. The first time with CMD_RESET as the first parameter and a string to analyze as the second. The string is copied to the internall buffer and then by calling the function again with CMD_NEXT as the first parameter we are getting the extracted CString in the second. Every time called it returns the next column of the given string. The function returns the index of the extracted column or -1 if there is not another column in the given string.
So by using the AddString we are adding data to the listbox and by using GetText we are getting a string from it. By calling ExtractString we are getting the columns of the above string.
- The list box is connected to the edit controls above it. This is done
by handling the ON_LBN_SELCHANGE() event. You can read the
CPizzaDlg::OnSelchange() in order to understand how we can use
You can read the CPizzaDlg::OnAddNew() in order to see how we can format the strings we add to the list box.
- I am using the AddNew() and Update() to add a record to my database
I am using SQL commands to delete, modify and find records. I am using
CDaoRecordset because when I used CRecordset I found that there was
a problem when I used LIKE '*' in my SQL question. CDatabase was
searching for the * in my database, didn't used it as a balanter.
- CPizzaDlg::PopulateLB() is an example of how you can populate the
list box with database records.
- The sample application is a simple addresser. To find a record you
give an id or any other information ( SurName, SecondName, ... ), you
can give only the first letters. If you give the id the other fields
are ignored. Then press find. When pressing the Add Button, you are
adding a record, and Delete deletes it. You can also modify the
selected record. If you want to see all the records just leave the
edit boxes empty and press the find button.
Last updated: 4 July 1998