// base.h
#ifndef base_h_
#define base_h_

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

class MainFrame: public wxFrame {
public:
    MainFrame( const wxString& title);
    wxTextCtrl* firstnumber;
    wxTextCtrl* secondnumber;
    wxTextCtrl* sum;
    void add(wxCommandEvent& event);
};

#endif

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

IMPLEMENT_APP(MainApp)

bool MainApp::OnInit() {
    MainFrame *MainWin = new MainFrame(_T("gui"));
    MainWin->Show(TRUE);
    SetTopWindow(MainWin);
    return TRUE;
}

MainFrame::MainFrame(const wxString& title): wxFrame((wxFrame*)NULL, -1, title) {
    wxPanel* panel = new wxPanel(this);
    wxStaticText* firstnumberstatic = new wxStaticText(panel, wxID_ANY, "First number");
    firstnumber = new wxTextCtrl(panel,wxID_ANY);
    wxStaticText* secondnumberstatic = new wxStaticText(panel, wxID_ANY, "Second number");
    secondnumber = new wxTextCtrl(panel,wxID_ANY);
    wxButton* add = new wxButton(panel,3,"add");
    wxStaticText* sumstatic = new wxStaticText(panel, wxID_ANY, "Sum");
    sum = new wxTextCtrl(panel,wxID_ANY);
    wxBoxSizer* panelSizer = new wxBoxSizer(wxVERTICAL);
    panelSizer->Add(firstnumberstatic, wxSizerFlags().Center());
    panelSizer->Add(firstnumber, wxSizerFlags().Center());
    panelSizer->Add(secondnumberstatic, wxSizerFlags().Center());
    panelSizer->Add(secondnumber, wxSizerFlags().Center());
    panelSizer->Add(add, wxSizerFlags().Center());
    panelSizer->Add(sumstatic, wxSizerFlags().Center());
    panelSizer->Add(sum, wxSizerFlags().Center());
    panel->SetSizer(panelSizer);
    wxBoxSizer* frameSizer = new wxBoxSizer(wxVERTICAL);
    frameSizer->Add(panel, wxSizerFlags().Expand());
    SetSizer(frameSizer);
    Bind(wxEVT_BUTTON, MainFrame::add, this, 3);
}

void MainFrame::add(wxCommandEvent& event) {
    sum->SetValue(wxString::Format(_T("%i"),wxAtoi(firstnumber->GetValue())+wxAtoi(secondnumber->GetValue())));
}

// base.h
#ifndef base_h_
#define base_h_

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

class MainFrame: public wxFrame {
public:
    MainFrame( const wxString& title);
    wxTextCtrl* sum;
    wxPanel* panel;
    void add(wxCommandEvent& event);
};

#endif

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

IMPLEMENT_APP(MainApp)

bool MainApp::OnInit() {
    MainFrame *MainWin = new MainFrame(_T("gui"));
    MainWin->Show(TRUE);
    SetTopWindow(MainWin);
    return TRUE;
}

MainFrame::MainFrame(const wxString& title): wxFrame((wxFrame*)NULL, -1, title) {
    panel = new wxPanel(this);
    wxBoxSizer* panelSizer = new wxBoxSizer(wxVERTICAL);
    panelSizer->Add(new wxStaticText(panel, wxID_ANY, "First number"), wxSizerFlags().Center());
    panelSizer->Add(new wxTextCtrl(panel, 1), wxSizerFlags().Center());
    panelSizer->Add(new wxStaticText(panel, wxID_ANY, "Second number"), wxSizerFlags().Center());
    panelSizer->Add(new wxTextCtrl(panel,2), wxSizerFlags().Center());
    panelSizer->Add(new wxButton(panel,3,"add"), wxSizerFlags().Center());
    panelSizer->Add(new wxStaticText(panel, wxID_ANY, "Sum"), wxSizerFlags().Center());
    panelSizer->Add(new wxTextCtrl(panel,4), wxSizerFlags().Center());
    panel->SetSizer(panelSizer);
    wxBoxSizer* frameSizer = new wxBoxSizer(wxVERTICAL);
    frameSizer->Add(panel, wxSizerFlags().Expand());
    SetSizer(frameSizer);
    Bind(wxEVT_BUTTON, MainFrame::add, this, 3);
}

void MainFrame::add(wxCommandEvent& event) {
    dynamic_cast<wxTextCtrl*>(panel->FindWindowById(4))->SetValue(wxString::Format(_T("%i"),wxAtoi(dynamic_cast<wxTextCtrl*>(panel->FindWindowById(1))->GetValue())+wxAtoi(dynamic_cast<wxTextCtrl*>(panel->FindWindowById(2))->GetValue())));
}