How to determine which component has the program focus in C++Builder

Question

I am using C++Builder XE4 32bit VCL platform. I am writing for Windows OS.

I have a MainForm with a lot of components on it. When I press a keyboard arrow key and the Form's OnShortCut event is triggered, how do I determine which component has the program focus?

I have different actions which must be taken based on which component has the focus.

void __fastcall TMainForm::FormShortCut(TWMKey &Msg, bool &Handled)
{
    //determine which component has the focus.
}

Answer 1

Use the global Screen->ActiveControl property:

Indicates which control currently has input focus on the screen.

Read ActiveControl to learn which windowed control object in the active form currently receives the input from the keyboard.

void __fastcall TMainForm::FormShortCut(TWMKey &Msg, bool &Handled)
{
    TWinControl *ctrl = Screen->ActiveControl;
    if (ctrl == Control1)
    {
        // do something...
    }
    else if (ctrl == Control2)
    {
        // do something else...
    }
    // and so on...
}

Or, you can use the Form's own ActiveControl property:

Specifies the control that has focus on the form.

Use ActiveControl to get or set the control that has focus on the form. Only one control can have focus at a given time in an application.

If the form does not have focus, ActiveControl is the control on the form that will receive focus when the form receives focus.

void __fastcall TMainForm::FormShortCut(TWMKey &Msg, bool &Handled)
{
    TWinControl *ctrl = this->ActiveControl;
    if (ctrl == Control1)
    {
        // do something...
    }
    else if (ctrl == Control2)
    {
        // do something else...
    }
    // and so on...
}