OnActiveControlChange (C++)

Description

This example uses the OnActiveControlChange event to detect when focus changes on the form. When focus changes, the hint for the active control is displayed on the status bar. To use this example, you must add a status bar to the form and set its SimplePanel property to True. Add a new public procedure, ActiveControlChanged, to the TForm1 class declaration.

Code

void _fastcall TForm1::ActiveControlChanged(System::TObject *Sender)
{
  TWinControl *Active = NULL;
  for (int I = 0; I < Form1->ControlCount; I++)
  {
	TWinControl *Temp = dynamic_cast<TWinControl *>(Form1->Controls[I]);
	if (Temp && Temp->Focused())
	  Active = Temp;
  }
  if ((Active != NULL) && (Active->Hint != ""))
	StatusBar2->SimpleText = GetLongHint(Active->Hint) + " focus";
}

void __fastcall TForm1::MouseOverChanged(TObject *Sender)
{
  TWinControl *Active = dynamic_cast<TWinControl *>(Sender);
  if (Active != NULL)
	StatusBar1->SimpleText = GetLongHint(Active->Hint) + " mouse over";
}

/*
Assign this method as the OnActiveControlChange event handler 
by setting it from the form's OnCreate event handler.
*/
__fastcall TForm1::TForm1(TComponent* Owner)
  : TForm(Owner)
{
  Screen->OnActiveControlChange = ActiveControlChanged;
}

/*
Make sure you clean up the screen object when the form is
freed by adding this OnDestroy event handler to the form:
*/
void __fastcall TForm1::FormDestroy(TObject *Sender)
{
  Screen->OnActiveControlChange = 0;
}

Uses

• Vcl.Forms.TScreen.OnActiveControlChange ( fr | de | ja )
• Vcl.Controls.TWinControl.Focused ( fr | de | ja )
• Vcl.Forms.TCustomForm.OnDestroy ( fr | de | ja )