Events
Table of Contents

The wxUpdateUIEvent event

Introduction

The wxUpdateUIEvent (wxWidgets: wxUpdateUIEvent Class Reference) class is used to give widgets the opportunity to update their state. A common use case would be a menu item that needs to be enabled or disabled based on some condition. The menu item can register a handler for the wxUpdateUIEvent event and in that handler check the condition and enable or disable itself.

Example

The full source for this example is available from our GitHub repository: wxWidgetsTutorials/Events/UpdateUIEvent1.

File: Events/UpdateUIEvent1/src/UpdateUIEvent1Frame.h

GitHub Copy

#ifndef _TUTORIALS_WXWIDGETS_UPDATEUIEVENT1FRAME_H_
#define _TUTORIALS_WXWIDGETS_UPDATEUIEVENT1FRAME_H_

#include <wx/frame.h>
#include <wx/checkbox.h>

class UpdateUIEvent1Frame : public wxFrame
{
public:
    UpdateUIEvent1Frame(const wxString& title);

private:
    void OnExit(wxCommandEvent& event);
    void OnExitUpdate(wxUpdateUIEvent& evt);

private:
    wxCheckBox* m_checkbox;

    wxDECLARE_EVENT_TABLE();
};

#endif

File: Events/UpdateUIEvent1/src/UpdateUIEvent1Frame.cpp

GitHub Copy

#include "UpdateUIEvent1Frame.h"
#include <wx/menu.h>
#include <wx/panel.h>

UpdateUIEvent1Frame::UpdateUIEvent1Frame(const wxString& title)
    : wxFrame(NULL, wxID_ANY, title, wxDefaultPosition, wxSize(250, 150)), m_checkbox(0)
{
    wxMenuBar* menuBar = new wxMenuBar;

    wxMenu* menuFile = new wxMenu;
    menuFile->Append(wxID_EXIT);
    menuBar->Append(menuFile, "&File");

    SetMenuBar(menuBar);

    // Add a checkbox that will determine
    // whether the Exit menu is enabled or not
    wxPanel* panel = new wxPanel(this);
    panel->SetBackgroundColour(*wxWHITE);
    m_checkbox = new wxCheckBox(panel, wxID_ANY, "Enable Exit menu", 
        wxPoint(50, 30));
}

void UpdateUIEvent1Frame::OnExit(wxCommandEvent& event)
{
    Close(true);
}

void UpdateUIEvent1Frame::OnExitUpdate(wxUpdateUIEvent& evt)
{
    evt.Enable(m_checkbox->GetValue());
}

wxBEGIN_EVENT_TABLE(UpdateUIEvent1Frame, wxFrame)
    EVT_MENU(wxID_EXIT, UpdateUIEvent1Frame::OnExit)
    EVT_UPDATE_UI(wxID_EXIT, UpdateUIEvent1Frame::OnExitUpdate)
wxEND_EVENT_TABLE()

The rest of the files don't have any significant changes but are shown here for completeness.

File: Events/UpdateUIEvent1/src/UpdateUIEvent1App.h

GitHub Copy

#ifndef _TUTORIALS_WXWIDGETS_UPDATEUIEVENT1APP_H_
#define _TUTORIALS_WXWIDGETS_UPDATEUIEVENT1APP_H_

#include <wx/app.h>

class UpdateUIEvent1App : public wxApp
{
public:
    virtual bool OnInit();
};

#endif

File: Events/UpdateUIEvent1/src/UpdateUIEvent1App.cpp

GitHub Copy

#include "UpdateUIEvent1App.h"
#include "UpdateUIEvent1Frame.h"

wxIMPLEMENT_APP(UpdateUIEvent1App);

bool UpdateUIEvent1App::OnInit()
{
    UpdateUIEvent1Frame* frame = new UpdateUIEvent1Frame("UpdateUIEvent1");
    frame->Show(true);
    return true;
}