在 TPanel 上做图

Delphi 的TPanel 是没有 Canavs属性的，因此无法直接在上面绘制图形。用下面的方法可以绕过限制，实现绘图的功能。

示例代码：

unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls, StdCtrls;

type
  TForm2 = class(TForm)
    Panel1: TPanel;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.Button1Click(Sender: TObject);
var
  PanelCanvas:TControlCanvas;
begin
  PanelCanvas:=TControlCanvas.Create;
  PanelCanvas.Control:=panel1;
  with PanelCanvas do
  begin
      pen.Color:=clGreen;
      pen.Width:=5;
      MoveTo(0,0);
      LineTo(Panel1.Width,Panel1.Height);

      MoveTo(Panel1.Width-1,0);
      LineTo(0,Panel1.Height);
  end;

  PanelCanvas.Free;
end;

end.

按下Button后，会在 Panel 对角线绘制直线。

代码和可执行文件下载

DrawOnPanel