按住panel 拖动窗体的方法

有些时候，我们的窗体没有 顶部栏，比如：窗体的borderstyle = bsNone; 我们想在顶部放置一个panel，来拖动窗体，方法如下，直接上代码了：

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Panel1: TPanel;
    procedure Panel1MouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure Panel1MouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure Panel1MouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  private
    { Private declarations }
    /// <summary>
    /// 鼠标左键是否按下了
    /// </summary>
    leftDown: Boolean;

    /// <summary>
    /// 鼠标左键按下时，鼠标的位置
    /// </summary>
    oldX: Integer;
    oldY: Integer;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Panel1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  if Button = mbLeft then
  begin
    leftDown := True;
    oldX := x;
    oldY := y;
  end;
end;

procedure TForm1.Panel1MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if leftDown then
  begin
    Left := Left + (x - oldX);
    Top := Top + (y - oldY);
  end;
end;

procedure TForm1.Panel1MouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  leftDown := False;
end;

end.

效果如下：