delphi事件参数sender的用法例程

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作者: 猪悟能 | 分类: delphi基础语法 | 浏览: 162 | 评论: 暂时没有评论

注意，如果你想为上面每个按钮做一个onclick是一种错误的思想，正确的做法是全选这5个按钮，然后做它们的onclick事件。
写如代码： Edit1.Text:=Edit1.Text+ TButton(Sender).Caption;

事件处理函数Sender:TObject参数，代表着“激发这个事件函数的控件”。我们可以把这个参数转为具体的类型，来访问控件实例。该参数往往和控件的Tag属性配合使用，对于简单事件函数的调用，如果我们确定参数中没用到Sender，可以用nil来充当Sender参数。

下面是源代码：
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unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    Edit1: TEdit;
    procedure Button1Click(Sender: TObject);
p rivate
    { Private declarations }
public
    { Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
Edit1.Text:=Edit1.Text+ TButton(Sender).Caption;
end;

end.

界面代码：
--------------------------------------------------------

object Form1: TForm1
Left = 275
Top = 274
Width = 340
Height = 264
Caption = 'Sender演示猪悟能'
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
PixelsPerInch = 96
TextHeight = 13
object Button1: TButton
    Left = 42
    Top = 23
    Width = 75
    Height = 25
    Caption = '1'
    TabOrder = 0
    OnClick = Button1Click
end
object Button2: TButton
    Left = 42
    Top = 56
    Width = 75
    Height = 25
    Caption = '2'
    TabOrder = 1
    OnClick = Button1Click
end
object Button3: TButton
    Left = 42
    Top = 90
    Width = 75
    Height = 25
    Caption = '3'
    TabOrder = 2
    OnClick = Button1Click
end
object Button4: TButton
    Left = 42
    Top = 124
    Width = 75
    Height = 25
    Caption = '4'
    TabOrder = 3
    OnClick = Button1Click
end
object Button5: TButton
    Left = 42
    Top = 157
    Width = 75
    Height = 25
    Caption = '5'
    TabOrder = 4
    OnClick = Button1Click
end
object Edit1: TEdit
    Left = 131
    Top = 24
    Width = 121
    Height = 21
    TabOrder = 5
end
end

源代码下载：http://www.rayfile.com/files/63599be3-23f0-11df-bedc-0015c55db73d/

第二个例子：
加个pageControl控件，计划用5个按钮去控制5个页标签。

首先把按钮的tag标签设好，为0-4
然后在按钮的onclick事件中加入代码：PageControl1.ActivePageIndex:=TComponent(Sender).Tag;

源代码下载：http://www.rayfile.com/files/71db0ac0-23f2-11df-be1d-0015c55db73d/