wxWidgets Example - it's very simple, but difficult for me..

It's very simple program, but very difficult for me at that time.
cause, I'm newbie.

i made this to use wxWidget sample project layout.

//============================================================================
// Name        : prjEx02.cpp
// Author      : stekilove@gmail.com
// Version     :
// Copyright   : Copy right stekilove@gmail.com.
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <wx/wxprec.h>
#ifndef WX_PRECOMP
   #include <wx/wx.h>
#endif

#include "wx/statline.h"

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

class MainFrame: public wxFrame
{
  public:
      MainFrame(const wxString &title, const wxPoint &pos, const wxSize &size);
      wxButton *btnOk;
      wxTextCtrl * wtcOutput;
      wxTextCtrl * wtcAnswer;
      void onQuit(wxCommandEvent &event);
      void onButtonOk(wxCommandEvent &event);
      void onTextAnswerEnter(wxCommandEvent &event);
  private:
      DECLARE_EVENT_TABLE()
};

enum
{
   ID_MAINWIN_QUIT = wxID_HIGHEST+1
   , ID_BUTTON_OK
   , ID_BUTTON_NEXT
   , ID_TEXT_ANSWER_ENTER
};


BEGIN_EVENT_TABLE(MainFrame, wxFrame)
    EVT_MENU(ID_MAINWIN_QUIT, MainFrame::onQuit)
    EVT_BUTTON(ID_BUTTON_OK, MainFrame::onButtonOk)
    EVT_TEXT_ENTER(ID_TEXT_ANSWER_ENTER, MainFrame::onTextAnswerEnter)
END_EVENT_TABLE()

IMPLEMENT_APP(MainApp)

bool MainApp::OnInit()
{
   MainFrame *win = new MainFrame(_("Frame"), wxPoint (100, 100), wxSize(450, 340));
   win->Show(TRUE);
   SetTopWindow(win);

   return TRUE;
}

MainFrame::MainFrame(const wxString &title, const wxPoint &pos, const wxSize &size)
    : wxFrame((wxFrame *) NULL, -1, title, pos, size)
{
    wxMenu *FileMenu = new wxMenu;
    wxMenuBar *MenuBar = new wxMenuBar;

    FileMenu->Append(ID_MAINWIN_QUIT, _("&Quit 종료."));

    MenuBar->Append(FileMenu, _("&File"));
    SetMenuBar(MenuBar);

    CreateStatusBar(2);
    SetStatusText(_("Welcome my steki world!"));

    //=====================================================
    //TODO: steki's coding...

    // make main panel..
    wxPanel *p = new wxPanel(this,-1);

    // make component..
    wxStaticBox *sb = new wxStaticBox(p, wxID_ANY, _T("Image or picture"));
    wxStaticText *st = new wxStaticText( p, wxID_ANY, _T("Steki and Tong loves each other!!"));
    wtcOutput = new wxTextCtrl( p, wxID_ANY, _T("some output text.."), wxDefaultPosition, wxSize(100,60), wxTE_MULTILINE );
    wxStaticLine *sl = new wxStaticLine( p, wxID_ANY, wxDefaultPosition, wxSize(3,3), wxHORIZONTAL);
    wxStaticText *stAnswer = new wxStaticText(p, wxID_ANY, _T("Label"));
    wtcAnswer = new wxTextCtrl(p, ID_TEXT_ANSWER_ENTER, _T(""), wxDefaultPosition, wxDefaultSize, wxTE_PROCESS_ENTER);
    wxButton *btnNext = new wxButton( p, ID_BUTTON_NEXT, _T("Next"));
    btnOk = new wxButton( p, ID_BUTTON_OK, _T("Ok"));

    // add component into layout..
    wxBoxSizer *statsizer = new wxStaticBoxSizer( sb , wxVERTICAL );
    statsizer->Add (  st        ,    wxSizerFlags().Align(wxALIGN_LEFT).Border(wxALL, 30));

    wxGridSizer *gridsizer = new wxGridSizer(2, 5, 5);
    gridsizer->Add(  stAnswer    , wxSizerFlags().Align(wxALIGN_RIGHT | wxALIGN_CENTER_VERTICAL));
    gridsizer->Add(  wtcAnswer    , wxSizerFlags(1).Align(wxGROW | wxALIGN_CENTER_VERTICAL));

    wxBoxSizer *button_box = new wxBoxSizer( wxHORIZONTAL );
    button_box->Add(  btnOk        , wxSizerFlags().Border(wxALL, 7));
    button_box->Add(  btnNext    , wxSizerFlags().Border(wxALL, 7));

    wxBoxSizer *topsizer = new wxBoxSizer( wxVERTICAL );
    topsizer->Add(  statsizer    , wxSizerFlags(1).Expand().Border(wxALL & ~wxBOTTOM, 10));
    topsizer->Add(  wtcOutput     , wxSizerFlags(1).Expand().Border(wxALL, 5) );
    topsizer->Add(    sl            ,wxSizerFlags().Expand());
    topsizer->Add(  gridsizer     , wxSizerFlags().Expand().Expand().Border(wxALL, 1) );
    topsizer->Add(  button_box     , wxSizerFlags().Center() );

    p->SetSizer( topsizer );

    topsizer->SetSizeHints( this );
}

void MainFrame::onQuit(wxCommandEvent & WXUNUSED(event))
{
    int answer = wxMessageBox("Quit program?", "Confirm", wxYES_NO, this);
    if (answer == wxYES)
        Close(TRUE);
}

void MainFrame::onButtonOk(wxCommandEvent & WXUNUSED(event))
{
    int answer = wxMessageBox("Quit program?", "Confirm", wxYES_NO | wxCANCEL, this);
    if (answer == wxYES)
        Close(TRUE);
}

void MainFrame::onTextAnswerEnter(wxCommandEvent & WXUNUSED(event))
{
    wtcOutput->AppendText( wtcAnswer->GetValue().Append("\n") );
    wtcAnswer->Clear();
}