如何让用户移动或拖动表单上的按钮？

Question

我有一个表单，我以编程方式创建了一个按钮：

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.

如何通过拖动来让用户在表单上移动FTableButton？

Answer 1

通过实施控件的var i = 0; $('.groepen option').each(function(){ $(this).attr('title',// Get the correct description somehow?) i++; }); ，OnMouseDown和OnMouseMove事件，您可以允许用户像这样移动它：

OnMouseUp

这里我们在表单中添加了三个新过程：

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.

我们已将这些程序指定为新 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); 事件的处理程序：

FTableButton

单击按钮时，您需要在放置单击时存储控件的位置和鼠标位置，以及鼠标当前向下。为此使用了三个新字段：

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

当移动鼠标时，您可以根据其原始位置以及点击时当前鼠标位置和鼠标位置之间的差异来更新控件的位置。