How to handle events (e.g. button click)

[ViRuSTriNiTy]

Hi there,

happy new year :)

i am new to this whole symbian os programming stuff and recently got started with it so dont kill me if i ask something stupid :).

ok heres the issue. because i am new to this stuff i want to create an application that simply handles a button click. so i digged in the uiq developer reference for words like "event", "click", "pointer" and so on. i came to the conclusion that a "button click" has to be a window server event. is that right?

my code looks pretty simple but the RunL() function that should be called when a event occures isnt called at all. i dont know why. i have written the following lines:

//first i declared my own class derived from CActive
class CNewClass : public CActive
{
..
// in the ConstructL functuion that is called from NewL / NewLC 
// i connect to the window server
void CNewClass::ConstructL()
{
 CActiveScheduler::Add( this );
 iWs.Connect();
 IssueRequest();
}

// Request window server events
void CNewClass::IssueRequest()
{
 iWs.EventReady(&iStatus); // request an event
 SetActive(); // now active
}

//the RunL method
void CNewClass::RunL()
{
 //here comes a few lines setting the text of a button to a
 //value of a counter variable, its my way to see wether the
 //RunL() is called or not
 ....

 //request further events
 IssueRequest();
}
...
}

I create an instance of the class when i click a menu entry.

I think this i how the howto describes it in the UIQ developer reference. So why is RunL() not called? (please dont answer with a link to the SDK SymbianNotCompatible\Graphics\WS\Simple example because it doesnt work, it crashes when i start the emulator and also it crashes on my P1i)

Another question. I dont really understand how the scheduler can call a RunL() method of an CActive object when i didnt pass an reference of my object on requesting an event? This totally confuses me because there are a sample where a timer is created to get a periodically event (e.g. each 1 second), but the timer is created just like this without any reference to anything but this sample works on my machine ?!?.

I hope you understand what i want to say.

Thx in advance for helping.

[morjens]

Yo!

Before calling EventReady(&iStatus) you need to enable events you want to capture. This via RWindowGrop::CaptureKey. I assume your application is not a UI application since you need to capture keys via window server. Thus, you need to create a window group also.

[ViRuSTriNiTy]

Hi,

sorry but its an UI application. i began from scratch wirh a simple uiq UI appllication c++ project. i also dont want to capture key strokes at the moment, i want to get an button click event. the button is clicked via the touchscreen of my P1i.

any ideas?

thx in advance.

:edit:

i followed a hint with HandlePointerEventL and i came to an solution. this solution is not state of the art i think but useable for me. by throwing away the active object idea and overriding the event handler method i can now handle a button click this way:

// i simply override the event handler method in my view to get a pointer event of my touchscreen
void CTestView::HandlePointerEventL(const TPointerEvent& aPointerEvent)
{
 if (aPointerEvent.iType == TPointerEvent::EButton1Up)
 {
  CEikTextButton* button = LocateControlByUniqueHandle<CEikTextButton>(ETestButtonCtrl);

  if (button->Rect().Contains(aPointerEvent.iPosition))
  {
   _LIT(tt,"Clicked");
   button->SetTextL(tt,CEikCommandButtonBase::EFirst);
   button->DrawNow();
  }
 }

 CQikViewBase::HandlePointerEventL(aPointerEvent);
}

You can see how i determine which control was clicked. I ask myself, isnt there a better way to do this? Lets imagine a view that has a huge amount of buttons. In this view i have to loop over this->Controls() to get the control that was clicked. in other programming languages i can use ControlFromPoint() or something like that to determine the control at the specific point. Isnt there a function in symbian c++?

Second question is, how can i "override" the HandlePointerEventL method of my button? In other languages like delphi i do something like

button.HandlePointerEventL = MyEventHandlerMethod;

When i do this in symbian c++ i get an error message that i fogot a "&" which is true in this case, but when i insert a & in front of MyEventHandlerMethod i get an error that in ISO C++ i cannot do this. Whats the trick here?

Perhaps i should create a new class derived from a button class and then override the method. But again, here i dont get a clue how to insert a button with my own class in the resource file.

i also found a way to handle a button click with a command button (it also works with other button types i think) and without using coordinates. just override the HandleControlEventL() method of the view. heres my solution (the example shows a click handler that toggles the dimmed state of the button):

void CTestView::HandleControlEventL(CCoeControl *aControl, TCoeEvent aEventType)
{
 switch(aEventType)
 {
  case EEventStateChanged:
  case EEventInteractionRefused:
  {
   if (aControl->UniqueHandle() == ETestButtonCtrl3) 
   {
    CEikCommandButton* b = LocateControlByUniqueHandle<CEikCommandButton>(ETestButtonCtrl3);

    TBool d = !b->IsDimmed();
    b->SetDimmed(d);
    b->DrawNow();
   }

   break;
  }
  default:
   CQikViewBase::HandleControlEventL(aControl, aEventType);
   break;
 }
}

Thx for helping.

:edit2:

i finally managed to achieve my goal by rethinking the idea of creating a own class for my button (thx to sander for guiding me to the correct path). here are the steps:

1. define a new class for your button derived from e.g. CEikTextButton
2. override HandlePointerEventL() and handle your stuff in here
3. create an instance of the button in ViewConstructL() of a view

now we have 3 solutions . anyway, if somebody can explain one of the things mentioned in this thread:

1. how i can assign a event handler to an existing button object
2. how can the active scheduler call a RunL() method of an CActive object when no reference of the concering object is passed on requesting an event

thx for helping.