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<td width="68%" background="DDl_back2.jpg" height="44"><big><big><font face="黑体"><p align="center">         Delphi编程                            (BM: strayli FlyingBoy)          </font></big></big></td></tr>
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<hr><p align="left"><small>发信人: fuse (保险丝), 信区: Visual <br>

标  题: Re: 在Delphi中动态生成的控件怎么响应消息？ <br>

发信站: BBS 水木清华站 (Thu Nov  6 16:02:51 1997) <br>

  <br>

【 在 FlyingBoy (一飞冲天鹰中王) 的大作中提到: 】 <br>

:                                      ^^^^^^^^^^^^^ <br>

:                                      不会吧，Help中好象说tag属性是没用的 <br>

:                                      只是一个为了兼容而声明的整数变量 <br>

  <br>

Control array emulation <br>

  <br>

Q.    "Is it possible to create something akin to the control array in VB? For eexample, I want an group of buttons with a common event handler whereby the event handler picks up an integer value for the particular button. In VB this would be done via <br>

the control array  index." <br>

  <br>

A.    One way do to this is to set the Tag field for each button to a different number and then create a common OnClick event handler that looks at the Sender's (as a TButton) Tag field.  Assign the same OnClick event handler to all the buttons in the <br>

group.  The OnClick event handler would look something like this: <br>

  <br>

  procedure TForm1.Button1Click(Sender: TObject); var cap: string; <br>

  begin <br>

    case TButton(sender).Tag of <br>

      1: ShowMessage('1st Button Pressed'); <br>

      2: ShowMessage('2nd Button Pressed'); <br>

      3: ShowMessage('3rd Button Pressed'); <br>



    end; <br>

  end; <br>

  <br>

Q:  I spend alot of time checking datatypes so that accessing the same property <br>

of different objects does GPF. <br>

  <br>

The code tends to look like this: <br>

  <br>

fldname:=''; <br>

fld:=Components[I]; <br>

if (Components[I] is TDBedit) then <br>

  <br>

   fldname:=TDBEdit(fld).DataField <br>

else if (Components[I] is TDBLookupList) then <br>

   fldname:=TDBlookupList(fld).DataField <br>

else if (Components[I] is TDBLookupCombo)then <br>

   fldname:=TDBlookupCombo(fld).DataField <br>

else if (Components[I] is TDBListBox) then <br>

   fldname:=TDBListBox(fld).DataField <br>

else if (Components[I] is TDBComboBox) then <br>

   fldname:=TDBComboBOx(fld).DataField <br>

else if (Components[I] is TDBCheckBox) then <br>

else if (Components[I] is TDBCheckBox) then <br>

   fldname:=TDBCheckBox(fld).DataField <br>

else if (Components[I] is TDBRadioGroup) then <br>

  <br>

   fldname:=TDBRadioGroup(fld).DataField <br>

else if (Components[I] is TDBMemo) then <br>

   fldname:=TDBMemo(fld).DataField; <br>

  <br>

Is there a way to use the classtype property in a case statement? <br>

Would that be better? <br>

  <br>

  <br>

A:  No and yes.  I suggest that you declare constants that represent each class. <br>

  <br>

const <br>

  val_TEdit = 1; <br>

  val_TButton = 2; <br>

{etc, etc} <br>

  <br>

Then, set the tag of each object to equal the object's constant.  Then the case statement is easy. <br>

  <br>

case (sender as tComponent).tag of <br>

{ . . . } <br>

   fldname:=TDBMemo(fld).DataField; <br>

  <br>

Is there a way to use the classtype property in a case statement? <br>

Would that be better? <br>

  <br>

  <br>

A:  No and yes.  I suggest that you declare constants that represent each class. <br>

  <br>

const <br>

  val_TEdit = 1; <br>

  val_TButton = 2; <br>

{etc, etc} <br>

  <br>

Then, set the tag of each object to equal the object's constant.  Then the case <br>

  <br>

case (sender as tComponent).tag of <br>

{ . . . } <br>

end; <br>

  <br>

{ This code came from Lloyd's help file! } <br>

  <br>

-- <br>

※ 来源:·BBS 水木清华站 bbs.net.tsinghua.edu.cn·[FROM: 210.32.151.168] <br>

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