delphi 事件委托 -- 未看

http://hi.baidu.com/endlesslove137/blog/item/d3eb6f35d1dc089ba71e1269.html

1 {

2 使用委托，将方法做为别一个方法的参数传递的例子（回调）

3 }

4 unit Unit1;

5

6 interface

7

8 uses

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

10 Dialogs, StdCtrls;

11

12 type

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

14 TDelegateClassArray=array[0..1] of TDelegateClass;

15 TForm1 = class(TForm)

16 Button1: TButton;

17 Button2: TButton;

18 procedure Button1Click(Sender: TObject);

19 procedure Button2Click(Sender: TObject);

20 private

21 { Private declarations }

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

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

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

25 public

26 { Public declarations }

27 end;

28

29 var

30 Form1: TForm1;

31

32 implementation

33

34 {$R *.dfm}

35

36 { TForm1 }

37

38 procedure TForm1.doDelegate(Delegate:TDelegateClass;msg:string);

39 begin

40 if Assigned(Delegate) then

41 Delegate(msg);

42 end;

43

44 procedure TForm1.Button1Click(Sender: TObject);

45 begin

46 doDelegate(UserMethod,'test');//调用委托处理程序，显示test信息

47 end;

48

49 procedure TForm1.UserMethod(msg: string);

50 begin

51 showmessage(msg);

52 end;

53

54 procedure TForm1.Button2Click(Sender: TObject);

55 var

56 test:TDelegateClassArray;

57 begin

58 test[0]:=UserMethod;

59 test[1]:=UserMethod2;

60 doDelegate(test[0],'test');

61 doDelegate(test[1],'test');

62 end;

63

64 procedure TForm1.UserMethod2(msg: string);

65 begin

66 showmessage('这是第二个方法');

67 end;

68

69 end.