Trying to keep focus on a specific widget

[dodle]

I'm practicing my C++ and i'm trying to create a program that keeps it's focus on the text area no matter what. Here is my code:

#include <wx/wx.h>
#include <iostream>
using namespace std;

class MainWindow : public wxFrame
{
public: MainWindow(const wxString& title);

void LoseFocus(wxFocusEvent& event);

wxPanel *panel1;
wxTextCtrl *text_area;
wxButton *buttonA;
wxButton *buttonB;

wxBoxSizer *v_sizer;
wxBoxSizer *h_sizer;
};

MainWindow::MainWindow(const wxString& title)
: wxFrame(NULL, -1, title, wxDefaultPosition, wxSize(300,400),
wxDEFAULT_FRAME_STYLE & ~(wxRESIZE_BORDER|
wxRESIZE_BOX|wxMAXIMIZE_BOX))
{
panel1 = new wxPanel(this, -1);

text_area = new wxTextCtrl(panel1, -1);
text_area->SetFocus();
text_area->Connect(wxEVT_KILL_FOCUS, wxFocusEventHandler(MainWindow::LoseFocus));

buttonA = new wxButton(panel1, -1, wxT("A"));
buttonB = new wxButton(panel1, -1, wxT("B"));

h_sizer = new wxBoxSizer(wxHORIZONTAL);
h_sizer->Add(buttonA, 1, wxEXPAND);
h_sizer->Add(buttonB, 1, wxEXPAND);

v_sizer = new wxBoxSizer(wxVERTICAL);
v_sizer->Add(text_area, 5, wxEXPAND);
v_sizer->Add(h_sizer, 1, wxEXPAND);

panel1->SetSizer(v_sizer);

Center();
}

void MainWindow::LoseFocus(wxFocusEvent& event)
{
text_area->SetFocus();
}

class Calc : public wxApp
{
public : virtual bool OnInit();
};

IMPLEMENT_APP(Calc)

bool Calc::OnInit()
{
MainWindow *frame = new MainWindow(wxT("Calculator"));
frame->Show(true);
return true;
}


Right now, if I press one of the buttons I get "segmentation fault" in the terminal and the app shuts down. What am I doing wrong?

[dodle]

Something is wrong with the handler. If change it from:

void MainWindow::LoseFocus(wxFocusEvent& event)
{
text_area->SetFocus();
}
to:

void MainWindow::LoseFocus(wxFocusEvent& event)
{
cout << "Hello World" << endl;
}
I get a printout in the terminal of "Hello World". So the event is being caught, I'm just not setting up the handler right.... I guess.

[c174]

text_area->Connect(wxEVT_KILL_FOCUS, wxFocusEventHandler(MainWindow::LoseFocus));



Try to change the line above to


text_area->Connect(wxEVT_KILL_FOCUS, wxFocusEventHandler(MainWindow::LoseFocus),NULL,th is);

The extra arguments are optional data and the event sink, respectively. Here I just put "NULL" since no user data is to be transferred to the focus event. I put "this" since the focus event handler is a member of MainWindow.

If you were handling a COMMAND-event you could use Connect without going through the object that is generating the event (and without the "NULL,this" stuff), because wxWidgets has a system for propagating certain types of events until a handler is found. You can read about this in the docs. It's a little bit tricky ;)

[dodle]

Thanks very much. That is exactly what I was looking for.