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catching events from mdi Child window

Posted on 2002-05-27
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Medium Priority
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Last Modified: 2010-08-05
Hi All,

I have a mdi app with several mdichild forms. On the mdi parent window i have a toolbar with a button that creates the child window and disables the button :

procedure TFrmMain.ToolButton1Click(Sender: TObject);
begin
 FrmCompanySearch := TFrmCompanySearch.Create(Self);
 FrmCompanySearch.Show;
 ToolBar1.Buttons[0].Enabled := false;
end;

The childwindow has his own onclose handler :

procedure TFrmCompanySearch.FormClose(Sender: TObject;
  var Action: TCloseAction);
begin
  Action := caFree;
  FrmCompanySearch := nil;
end;

Now the Question : How do i enable the toolbarbutton after the onclose event. So how can i catch the childwindow on close in my mdi parent form !

I hope that its a bit clear,
Thanks in advance,

Yuri
0
Comment
Question by:muldeyur
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11 Comments
 
LVL 27

Expert Comment

by:kretzschmar
ID: 7038551
you could send a wm_user+xxx message to your mainform
and handle the message there,
or
you could access directly the mainform

in your child-closemethod

meikl ;-)
0
 

Author Comment

by:muldeyur
ID: 7038607
how do i access the Mainform directly?
do you have a code example?

regards

Yuri
0
 
LVL 27

Accepted Solution

by:
kretzschmar earned 400 total points
ID: 7038626
simplified (from head)

mainform:

type tform1 ....

     public
       Procedure Handle_ChildClose(AChild : TForm);
    ....

implementation

procedure tform1.Handle_ChildClose(AChild : TForm);
begin
  if (aform is TFrmCompanySearch) then
    ToolBar1.Buttons[0].Enabled := true;
  //..maybe more childclasses to handle
end;

------------

childform

...

implementation
uses mainformunit; //!include this with your real unit name

....
procedure TFrmCompanySearch.FormClose(Sender: TObject;
 var Action: TCloseAction);
begin
 Action := caFree;
 FrmCompanySearch := nil;
 mainformname.handle_ChildClose(self);
end;

------

hope this helps

meikl ;-)


0
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LVL 27

Expert Comment

by:kretzschmar
ID: 7038635
oops there is a typo

this line
if (aform is TFrmCompanySearch) then

should be
if (aChild is TFrmCompanySearch) then
   
;-)
   
0
 
LVL 9

Expert Comment

by:ginsonic
ID: 7038737
listening
0
 
LVL 27

Expert Comment

by:kretzschmar
ID: 7038748
nick, the listener ? :-)
0
 
LVL 2

Expert Comment

by:freshman3k
ID: 7040505
hello!

This should help you:

private
 { Private declarations }
 FClientInstance : TFarProc;
 FPrevClientProc : TFarProc;
 procedure ClientWndProc(var aMessage: TMessage);

implementation

procedure TfrmMForm.FormShow(Sender: TObject);
begin
FPrevClientProc := Pointer(GetWindowLong(ClientHandle, GWL_WNDPROC));
FClientInstance := MakeObjectInstance(ClientWndProc);
SetWindowLong(ClientHandle, GWL_WNDPROC, LongInt(FClientInstance));
end;

procedure TfrmMForm.FormClose(Sender: TObject);
begin
SetWindowLong(ClientHandle, GWL_WNDPROC, LongInt(FPrevClientProc));
end;

procedure TfrmMForm.ClientWndProc(var aMessage: TMessage);

procedure DoDefault;
 begin
    with aMessage do
      Result := CallWindowProc(FPrevClientProc,ClientHandle, Msg, wParam,lParam);
 end;

begin
  if aMessage.Msg = WM_MDIDESTROY then begin
     
{aMessage.Child is handle of the Mdi Child being closed}

    if aMessage.Child = FrmCompanySearch.Handle then begin    
        ToolBar1.Buttons[0].Enabled := true;
        end;
   
    if aMessage.Child = OtherMdiChildForm.Handle then
begin  
        ToolBar1.Buttons[1].Enabled := true;          
        end;
   
    DoDefault; {do defualt processing}
   end;
  else
    DoDefault;  {do defualt processing}
  end;
end;


Good Luck! ;-)
0
 
LVL 9

Expert Comment

by:ginsonic
ID: 7041013
Don't have time to answer all the time . So I "mark" :P the question and return latter . If is necesary .

So ...

const
  WM_DelChild = WM_User + 300;

type
  TMainForm = class(TForm)
...................................
private
    procedure CreateChild(const Name: string);
    procedure OnDelChild(var msg: TMessage); message WM_DelChild;  
    procedure OnChildDestroy(Sender: TObject);
.................

procedure TMainForm.OnDelChild(var msg: TMessage);
begin
  ShowMessage(' Just destroy me :( ');
end;

procedure TMainForm.OnChildDestroy(Sender: TObject);
begin
  PostMessage(TForm(MainForm).handle, WM_DelChild, 0, Integer(PChar('ChildName')));
end;

procedure TMainForm.CreateChild(const Name: String);
var
  Child: TChildForm;
begin
  Child := TChildForm.Create(Application);
  Child.Caption := Name;
  Child.OnDestroy := OnChildDestroy;
end;

0
 
LVL 9

Expert Comment

by:ginsonic
ID: 7041163
Sorry :

1. Child unit

const
  WM_CloseWin = WM_User + 300;

type
  TChildForm = class(TForm)
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  end;

var
  ChildForm: TChildForm;

implementation

{$R *.DFM}

procedure TChildForm.FormClose(Sender: TObject;
  var Action: TCloseAction);
var Buffer: array [0..99] of Char;
    s:string;
begin
  GetWindowText(TForm(Sender).Handle,buffer,100);
  s:=Buffer;
  PostMessage(Application.MainForm.handle, WM_CloseWin, 0, Integer(PChar(s)));
  Action := caFree;
end;

end.

2. Main unit

const
  WM_CloseWin = WM_User + 300;

type
  TMain = class(TForm)
...............
  private
    procedure OnCloseChild(var msg: TMessage); message WM_CloseWin;
    procedure CreateChild(const Name: string);
...............


procedure TMain.OnCloseChild(var msg: TMessage);
begin
  ShowMessage(Strpas(Pointer(msg.lparam)));
end;


0
 

Author Comment

by:muldeyur
ID: 7041170
Wow folks,

I'am going to try this when i get home,
Thanks to all that give advice,
will give the points as soon as i tried it!!

Regards,

Yuri
0
 

Author Comment

by:muldeyur
ID: 7042492
Thanks to all for the advice, but Kretzschmar was the quickest and also exactly what i Needed !

Thanks a lot,

Yuri
0

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