delphi - 如何让用户移动或拖动表单上的按钮？

Question

我有一个表单，我在其中以编程方式创建了一个按钮，如下所示:

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
  System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs,
  Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);        
  private
    FTableButton : TButton;       
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  if not Assigned(FTableButton) then begin
    FTableButton := TButton.Create(self);
    FTableButton.Parent := self;       
  end;
end;    

end.

如何让用户通过拖动来移动表单上的FTableButton？

Answer 1

通过实现控件的 OnMouseDown、OnMouseMove 和 OnMouseUp 事件，您可以允许用户像这样移动它:

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);        
  private
    FTableButton : TButton;
    FTableButtonDragging : boolean;
    FMouseDownLocation : TPoint;
    FButtonStartingLocation : TPoint;
    procedure TableButtonMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure TableButtonMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure TableButtonMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  if not Assigned(FTableButton) then begin
    FTableButton := TButton.Create(self);
    FTableButton.Parent := self;
    FTableButton.Caption := 'I am New';
    FTableButton.OnMouseDown := TableButtonMouseDown;
    FTableButton.OnMouseMove := TableButtonMouseMove;
    FTableButton.OnMouseUp := TableButtonMouseUp;
  end;
end;

procedure TForm1.TableButtonMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FTableButtonDragging := true;
  FMouseDownLocation := Mouse.CursorPos;
  FButtonStartingLocation := TPoint.Create(FTableButton.Left, FTableButton.Top);
end;

procedure TForm1.TableButtonMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if FTableButtonDragging then begin
    FTableButton.Left := FButtonStartingLocation.X + (Mouse.CursorPos.X - FMouseDownLocation.X);
    FTableButton.Top := FButtonStartingLocation.Y + (Mouse.CursorPos.Y - FMouseDownLocation.Y);
    FTableButton.Invalidate;
  end;
end;

procedure TForm1.TableButtonMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FTableButtonDragging := false;
end;

end.

这里我们向表单添加了三个新过程:

 procedure TableButtonMouseDown(Sender: TObject; Button: TMouseButton;
                                Shift: TShiftState; X, Y: Integer);
 procedure TableButtonMouseMove(Sender: TObject; Shift: TShiftState; 
                                X, Y: Integer);
 procedure TableButtonMouseUp(Sender: TObject; Button: TMouseButton;
                              Shift: TShiftState; X, Y: Integer);

我们已将这些过程指定为新 FTableButton 事件的处理程序:

FTableButton.OnMouseDown := TableButtonMouseDown;
FTableButton.OnMouseMove := TableButtonMouseMove;
FTableButton.OnMouseUp := TableButtonMouseUp;

单击按钮时，您需要存储控件的位置和单击时的鼠标位置，以及鼠标当前按下。为此使用了三个新字段:

FTableButtonDragging : boolean;
FMouseDownLocation : TPoint;
FButtonStartingLocation : TPoint;

当移动鼠标时，您可以根据控件的原始位置以及当前鼠标位置与单击时鼠标位置之间的差异来更新控件的位置。