Common Components

The power of Delphi lies in its vast Component Palette, which allows for Rapid Application Development (RAD). Mastering these common components is the first step in efficient UI building.

1. Basic Display and User Interaction

These components handle displaying static text and capturing simple, single-line input.

Example: Interacting with Input Components

To read data from a text box and display it:

procedure TForm1.btnGreetClick(Sender: TObject);
begin
  // Read the current text from the TEdit component
  var UserName := edtUserName.Text; 
  
  // Check the state of the TCheckBox
  if chkActive.Checked then
    ShowMessage('Welcome back, ' + UserName)
  else
    ShowMessage('User ' + UserName + ' is inactive.');
end;

2. Grouping and Organization Components

These controls are non-interactive containers used to organize and structure the UI, making the form cleaner and easier to navigate.

Tab Control Usage

The TPageControl and its nested TTabSheet components are essential for complex UIs:

1. Place a TPageControl on the form.
2. Right-click the TPageControl and select “New Page” to add a TTabSheet.
3. Change the TTabSheet‘s Caption property (this is the text visible on the tab).
4. Drop components (e.g., TEdit, TButton) directly onto the desired TTabSheet.

3. Selection Components

These components allow the user to select one or more items from a predefined list.

Working with Lists

Both TListBox and TComboBox use the Items property, which is a TStrings object. TStrings provides methods for easily managing the list of text lines:

// Example: Adding and clearing items in a ListBox
procedure TForm1.FormCreate(Sender: TObject);
begin
  // Add items programmatically
  cboOptions.Items.Add('Option A');
  cboOptions.Items.Add('Option B');
  cboOptions.Items.Add('Option C');
  
  // Set a default selection
  cboOptions.ItemIndex := 0; // Selects 'Option A'
end;

procedure TForm1.btnClearListClick(Sender: TObject);
begin
  // Clear all items from the list
  cboOptions.Items.Clear;
end;