Delphi 事件委託

轉自http://anony3721.blog.163.com/blog/static/5119742010731104255351/


 {
 使用委託，將方法做爲別一個方法的參數傳遞的例子（回調）
 }
 unit Unit1;
 
 interface
 
 uses
   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
   Dialogs, StdCtrls;
 
 type
   TDelegateClass=procedure(msg:string) of object;//定義一個委託
   TDelegateClassArray=array[0..1] of TDelegateClass;
   TForm1 = class(TForm)
     Button1: TButton;
     Button2: TButton;
     procedure Button1Click(Sender: TObject);
     procedure Button2Click(Sender: TObject);
   private
     { Private declarations }
     procedure UserMethod(msg:string);//委託指定的用戶自定義方法
     procedure UserMethod2(msg:string);//委託指定的用戶自定義方法2    
     procedure doDelegate(Delegate:TDelegateClass;msg:string);//如果委託實例存在，就執行委託
   public
     { Public declarations }
   end;
 
 var
   Form1: TForm1;
 
 implementation
 
 {$R *.dfm}
 
 { TForm1 }
 
 procedure TForm1.doDelegate(Delegate:TDelegateClass;msg:string);
 begin
   if Assigned(Delegate) then
   Delegate(msg);
 end;
 
 procedure TForm1.Button1Click(Sender: TObject);
 begin
   doDelegate(UserMethod,'test');//調用委託處理程序，顯示test信息
 end;
 
 procedure TForm1.UserMethod(msg: string);
 begin
   showmessage(msg);
 end;
 
 procedure TForm1.Button2Click(Sender: TObject);
 var
   test:TDelegateClassArray;
 begin
   test[0]:=UserMethod;
   test[1]:=UserMethod2;
   doDelegate(test[0],'test');
   doDelegate(test[1],'test');
 end;
 
 procedure TForm1.UserMethod2(msg: string);
 begin
   showmessage('這是第二個方法');
 end;
 
 end.