delphi 事件委托 -- 未看

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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.