TButton/fr

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Un TButton est un composant qui fournit un bouton à pousser de base. Il est disponible dans l'onglet Standard de la palette de composants.

Un TButton est une des contrôles les plus basiques sur une fiche. En cliquant dessus avec la souris ou en se plaçant dessus à l'aide de la touche [tab] et en actionnant ensuite [Entrée], une action est déclenchée. Ce clic est appelé un événement. Pour réaliser l'action, vous avez besoin d'un gestionnaire d'événement qui est appelé après le clic.

Vous pouvez ajouter un bouton sur votre fiche, en cliquant sur le bouton de la palette de composant Standard et le placer sur la fiche en cliquant dessus.

Le gestionnaire d'événement pour le clic souris peut être atteint facilement en double-cliquant sur le botoun posé (ou en passant par l'inspecteur d'objet, onglet Evénements). Le gestionnaire d'événement pour le Button1 de la Form1 ressemblera à cela :

procedure TForm1.Button1Click(Sender: TObject);
begin

end;

Entre les instructions begin et end, vous pourrez écrire du code qui est appelé quand Button1 est cliqué.

Almost all available beginner tutorials use TButtons as an easy entry into the Object Oriented Programming with Lazarus. Following tutorials are well suited for beginners to understand the use of buttons:

• The first GUI application for absolute beginners
• Your first Lazarus program tutorial for Lazarus
• Programming Example Object Oriented Programming with Free Pascal and Lazarus

Un simple exemple

• Create a new application and drop a TButton on the form.
• Doubleclick this Button1 on the form (the default handler: OnClick is created for Button1, the source text editor opens).
• Add following code in the event handler:

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowMessage('Lazarus makes my day');  //A message will be displayed with the content...
end;

• Start your program (with Key <F9>).

Clic-droit

Each TButton has an (optional) PopupMenu property that will activate a connected TPopupMenu whenever the button is right-clicked.

Boutons générés dynmaiquement

Sometimes, instead of creating buttons (or other components) with the Lazarus form designer, it is easier to create them dynamically at run time. This approach is useful especially if you have continually repeated buttons on a form.

This can be achieved as in the the following example (a quick calculator):

• Create a new blank GUI application with the form Form1 and add StdCtrls to the uses clause (here the TButton is).
• Change caption Form1 to QuickAdd.
• Create the OnCreate event handler of Form1 (go in the Object Inspector to the event OnCreate and click the button [...]).
• Add following code:

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
  aButton: TButton;
begin
  for i:=0 to 9 do begin              //create 10 Buttons 
    aButton:=TButton.Create(Self);    //create Button, Owner is Form1, where the button is released later
    aButton.Parent:=Self;             //determine where it is to be displayed
    aButton.Width:=aButton.Height;    //Width should correspond to the height of the buttons
    aButton.Left:=i*aButton.Width;    //Distance from left
    aButton.Caption:=IntToStr(i);     //Captions of the buttons (0.9)
    aButton.OnClick:=@aButtonClick;   //the event handler for the button -> will be created yet
  end;
  Self.Height:=aButton.Height;        //Height of the form should correspond to the height of the buttons
  Self.Width:=aButton.Width*10;       //Width of the form to match the width of all buttons
end;

• Now you must create the event handler for the button clicks.
• In the source editor, entering your class TForm1 in the section private.
• Add procedure aButtonClick(Sender: TObject); and then press the keys [CTRL] + [Shift] + [c] (the code completion becomes active and creates the procedure TForm1.aButtonClick(Sender: TObject);.
• Paste following code:

procedure TForm1.aButtonClick(Sender: TObject);
const
  Cnt: Integer = 0;
var
  i: Integer;
begin
  if (Sender is TButton) and                       //called the event handler of a button out?
     TryStrToInt(TButton(Sender).Caption, i)       //then try to convert the label in a integer
  then begin
    Cnt:=Cnt + i;                                 //the adding counter is incremented by the number of entrechende
    Caption:='QuickAdd: '+IntToStr(Cnt);          //write the result to the caption of the form
  end;
end;

• Start your application.

  Remarque: You can assign every imaginable event handlers to your buttons, as long as this the form procedure <class>.<name of procedure>(Sender: TObject); has. Thus, you can use one from another class!

Voir aussi

• Doc. TButton
• TBitBtn
• TSpeedButton
• TColorButton
• 15-puzzle (taquin) (Jeu)