一个简单的DELPHI自定义事件的例子(转)
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
?? //定義一個(gè)事件格式,要傳參數(shù)的格式 后面必須要加上of object
?? TeacherArgnyEvent = procedure(ErrorCount: Integer) of object;
type
TTeacher = class(TObject)
private
??? FStudentErrorCount: Integer;
??? FOnTeacherArngy: TeacherArgnyEvent; //定義一個(gè)內(nèi)部事件,private里的只能在TTeacher類內(nèi)部調(diào)用
??? procedure SetStudentErrorCount(Value: Integer);
public
??? constructor Create;
??? destructor Destroy; override;
??? property StudentErrorCount: Integer read FStudentErrorCount write SetStudentErrorCount ;
??? property OnTeacherArngy: TeacherArgnyEvent read FOnTeacherArngy write FOnTeacherArngy ; //定義一個(gè)外部的事件,在其它的對(duì)象里面可以通過(guò)FTeacher.ONTeacherArngy這樣調(diào)用。讀寫是通過(guò)內(nèi)部的FOnTeacherArngy
end;
type
TForm1 = class(TForm)
??? Button1: TButton;
??? procedure FormCreate(Sender: TObject);
??? procedure FormClose(Sender: TObject; var Action: TCloseAction);
??? procedure Button1Click(Sender: TObject);
??? procedure IfTeacherArngy(EC: Integer); //自己定義事件觸發(fā)時(shí)要執(zhí)行的函數(shù),和Button控件在事件列表中雙擊時(shí)出來(lái)的那段代碼一樣,只是這里是你自己定義的,而不是DELPHI給你生成的
private
??? FTeacher: TTeacher ;
public
??? { Public declarations }
end;
?
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TTeacher }
constructor TTeacher.Create;
begin
FStudentErrorCount := 0;
end;
destructor TTeacher.Destroy;
begin
inherited;
end;
procedure TTeacher.SetStudentErrorCount(Value: Integer);
begin
FStudentErrorCount := Value;
if FStudentErrorCount > 3 then??? //給StudentErrorCount賦值的時(shí)候,判斷是否觸發(fā)FOnTeacherArngy事件
??? if Assigned(FOnTeacherArngy) then?? //看FOnTeacherArngy是否為空,不為空則執(zhí)行該事件,如果不判斷是否為空,則執(zhí)行下面一句的時(shí)候可能會(huì)有錯(cuò)誤
????? FOnTeacherArngy(FStudentErrorCount);
end;
{ TForm }
procedure TForm1.FormCreate(Sender: TObject);
begin
FTeacher := TTeacher.Create ;???? //創(chuàng)建一個(gè)TTeacher的實(shí)例
FTeacher.OnTeacherArngy := IfTeacherArngy; //把FOrm1里的IfTeacherArngy過(guò)程賦值給FTeacher的OnTeacherArngy,這樣它就不為空了
end;
procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
FTeacher.Free ;?? //窗體關(guān)閉時(shí)釋放
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
FTeacher.StudentErrorCount := FTeacher.StudentErrorCount + 1; //給StudentErrorCount賦值 ,我只是給他賦值,就會(huì)觸發(fā)那個(gè)事件
// 有了這個(gè)類,就不用下面這一段了,給 StudentErrorCount屬性賦值就能達(dá)到下面這段代碼的效果。
// if FTeacher.StudentErrorCount > 3 then
//??? ShowMessage('Student 錯(cuò)誤了' + IntToStr(ec) + '次,老師生氣了。');
end;
procedure TForm1.IfTeacherArngy(EC: Integer);
begin
ShowMessage('Student 錯(cuò)誤了' + IntToStr(ec) + '次,老師生氣了。'); //事件觸發(fā)時(shí)的情況,和Button控件在事件列表中雙擊時(shí)出來(lái)的那段代碼一樣,只是這里是你自己定義的,而不是DELPHI給你生成的
end;
end.
轉(zhuǎn)載于:https://www.cnblogs.com/gaowen1210/archive/2011/05/24/2055125.html
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