Press Enter Twice

Hi, I`m new here and, of course, have a small problem.
I need to create a program with VC++ 6 Builder where:
Press ENTER once - open picture,
Press ENTER Twice - start a music.

I can`t figure out how to check if user press ENTER twice, can anybody help me?

My Code:
void __fastcall TForm1::ListBox1KeyPress(TObject *Sender, char &Key)
{
switch( Key )
{
case 'VK_RETURN':
{ atidarytpav(); }
break;
}

Quote:

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Originally Posted by alone882

My Code:
void __fastcall TForm1::ListBox1KeyPress(TObject *Sender, char &Key)
{
...
}

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What is TObject *Sender?

The :ListBox1KeyPress method takes a pointer to a TObject called Sender. Mostly, every event handler, in c++, will have at least a Sender parameter. When the button is clicked, the event handler (:ListBox1KeyPress) for the KeyPress event is called.

The parameter "Sender" references the control that was used to call the method. If you press on the ListBox1 control, causing the ListBox1KeyPress method to be called, a reference or pointer to the ListBox1 object is passed to ListBox1KeyPress in the parameter called Sender

Here is a (Microsoft) Visual C++ forum and not a (Borland) C++ Builder one.

However, is any problem for you to keep a member variable in TForm1 class which keeps the number of Enter keystrokes?

Quote:

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Originally Posted by alone882

The :ListBox1KeyPress method takes a pointer to a TObject called Sender. Mostly, every event handler, in c++, will have at least a Sender parameter. When the button is clicked, the event handler (:ListBox1KeyPress) for the KeyPress event is called.

The parameter "Sender" references the control that was used to call the method. If you press on the ListBox1 control, causing the ListBox1KeyPress method to be called, a reference or pointer to the ListBox1 object is passed to ListBox1KeyPress in the parameter called Sender

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Sorry, but my MSDN doesn't mention anything looking like TObject. And I don't need anything but TObject description in order to help you. :cool:

Quote:

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Originally Posted by alone882

every event handler, in c++, will have at least a Sender parameter.

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Probably in a library shipped with Borland C++ Builder. Not "in c++" in general.
As I already said, you have not posted in the right forum.

But how about - CodeGuru Forums > Visual C++ & C++ Programming > Visual C++ Programming ?

Quote:

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Originally Posted by alone882

But how about - CodeGuru Forums > Visual C++ & C++ Programming > Visual C++ Programming ?

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As stated it is:

Quote:

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Visual C++ Programming Ask questions about Windows programming with Visual C++ and help others by answering their questions.

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alone882 these days there are quite few that use Borland C++ Builder. Version 6 is also very old/outdated so I guess that will make it even harder to get help.

I would try http://embarcadero.com/ and see if they have a link to some C++ Builder community.

Quote:

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I can`t figure out how to check if user press ENTER twice, can anybody help me?

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This implies some waiting should be done after first Enter for a short period to see if the second Enter comes (similar to mouse double click logic).

The form starts timer (say, 200-500ms) on first Enter and set some flag which should be reset when the second Enter arrives before the timer elapses. In case another Enter arrives when the flag is set, it means "double Enter" event to fire (resetting the flag as well). In case timer elapses with the flag set (which means there was no second Enter within the period), it resets the flag and fires "single Enter" event.

Quote:

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Originally Posted by VictorN

Sorry, but my MSDN doesn't mention anything looking like TObject. And I don't need anything but TObject description in order to help you. :cool:

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Must be Borland's library. In .NET there is a base class called Object, from which everything derives. WinForms' implementation of event handler callbacks take two parameters, Object Sender and an event argument class. This looks to use the same concept. So a TObject pointer is just a base pointer to some control that is responsible for raising the event.

Quote:

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Originally Posted by Chris_F

Must be Borland's library.

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No, it might be and it might be not.
And the fact is there is not.

Quote:

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Originally Posted by Chris_F

In .NET there is a base class called Object, from which everything derives. WinForms' implementation of event handler callbacks take two parameters, ...

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Perhaps you should then ask it in the .NET forum? :rolleyes:

Quote:

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Originally Posted by VictorN

Perhaps you should then ask it in the .NET forum? :rolleyes:

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I am not the originator of this thread, so I have no need to ask this question anywhere. Even then, I merely stated that the code he posted is similar to .NET in design. However TObject is most assuredly not a part of the .NET library, so asking this question there would be extremely foolish.

Quote:

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Originally Posted by VictorN

No, it might be and it might be not.
And the fact is there is not.

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Admittedly I haven't done much research, but everything I've seen while searching seems to tie the TObject class to Borland/C++ and Delphi. Do I have any proof that this is what alone882 is using? No. But I'd be willing to make a wager that it is.

Lastly, I fail to see how this is even relevant. His problem isn't with his use of the GUI library, it's a simple problem that could arise in MFC, .NET, Delphi, or what have you. He simply needs to create a variable to store whether or not the button has been clicked previously to see which action should be taken.

Quote:

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Originally Posted by Chris_F

ILastly, I fail to see how this is even relevant. His problem isn't with his use of the GUI library, it's a simple problem that could arise in MFC, .NET, Delphi, or what have you. He simply needs to create a variable to store whether or not the button has been clicked previously to see which action should be taken.

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Well then, a quick answer?

Ok I have this script

Code:

---

int pressCount = 0;
void __fastcall TForm1::ListBox1KeyPress(TObject *Sender, char &Key)
{
 
switch( Key )
  {
  case  'VK_RETURN':
  {
      atidarytpav();
      pressCount = ++pressCount % 2 }
      if (count != 0)
      {
        //first time
      }
      else
      {
        //second time
        pressCount = 0;
      }

  break;
}

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but now say

Code:

---

Undefined symbol 'count'

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Do I need some library or what .. ?

You need to understand the code you write. Precisely, what count means and how it differs from pressCount. :)

Then you need to think about exact meaning of "press Enter twice". If you press Enter and wait 24 hours before pressing Enter second time, will it be two "single presses" or a single "press twice"? Your code tells me the second is true. Now you tell yourself whether it is.

if (count != 0)

where did you defined count ?

Sry, but this code wont work I try

Code:

---

switch( Key )
  {
  case  'VK_RETURN':
  {
      pressCount = ++pressCount % 2 }
      if (pressCount != 0)
      {
        //first time
      }
      else
      {
        //second time
        pressCount = 0;
      }

  break;

---

And

Code:

---

int pressCount = 0;
switch( Key )
  {
  case 'VK_RETURN:
  {
      if (pressCount == 0)
      {
        //first time
        ++pressCount;
      }
      else
      {
        //second time
        pressCount = 0;
      }
    }
  break;

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No one will work

Pls somebody help :/

Quote:

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No one will work

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... until you make pressCount be static.

Finally I figure out how to solve this problem, thank you Igor

You're welcome. :)

count isnt defined anywhere (in scope or in class declaration)

If still not solved here is code snippet.

Code:

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BOOL CTESDlg::PreTranslateMessage(MSG* pMsg)
{
        static int co = 0;

        if (pMsg->message == WM_KEYDOWN && pMsg->wParam == VK_RETURN)
        {
                pMsg->wParam = NULL;
                ++co;

                if (co==2)
                        AfxMessageBox(L"Twice Pressed");
        }
       
        return CDialog::PreTranslateMessage(pMsg);
}

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