Delphi 事件委托

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

{

使用委托，将方法做为别一个方法的参数传递的例子（回调）

}

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

Dialogs, StdCtrls;

type

TDelegateClass=procedure(msg:string) of object;//定义一个委托

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);//委托指定的用户自定义方法

procedure UserMethod2(msg:string);//委托指定的用户自定义方法2

procedure doDelegate(Delegate:TDelegateClass;msg:string);//如果委托实例存在，就执行委托

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');//调用委托处理程序，显示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('这是第二个方法');

end;

end.