Question

I’m developing a ebook manager on Lazarus, but I’m having some troubles with a component that I’ve never used(TListBox). On the TListBox named CategoryList, I have these items:

Literature and Fiction
Romance
Computers and Internet
Poetry
Professional and Technical
Science Fiction and Fantasy
Biographies and Memoirs
Business and Finance
Children’s Books
Entertainment
History
Science
Self-Help
Textbooks and Educational Materials
Travel
Westerns

When the user select an item on the CategoryList, I want to store it in a variable, but how can I do this?

Answer 1

If you want the index:

index := CategoryList.ItemIndex;

If you want the string:

str := CategoryList.Items[CategoryList.ItemIndex];

To capture the moment the user selects something, you need to register an OnChange event:

CategoryList.OnChange := CategoryListChange;

Where the CategoryListChange is an event listener:

procedure TMyForm.CategoryListChange(Sender: TObject);
begin
  // do something with CategoryList.Items[CategoryList.ItemIndex]
end; 

You might want to look on some of the posts on this webpage too!