wxwidget -- Hello World

This mini tutorial aims to help people make quick judgements concerning syntax and basic principles. The complete Hello World program is here

You have to include wxWidgets's header files, of course. This can be done on a file by file basis (such as #include "wx/window.h") or using one global include (#include "wx/wx.h"). This is also useful when using precompiled headers.

#include "wx/wx.h"

Practically every app should define a new class derived from wxApp. By overriding wxApp's OnInit() the program can be initialized, e.g. by creating a new main window.

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

The main window is created by deriving a class from wxFrame and giving it a menu and a status bar in its constructor. Also, any class that wishes to respond to any "event" (such as mouse clicks or messages from the menu or a button) must declare an event table using the macro below. Finally, the way to react to such events must be done in "handlers". In our sample, we react to two menu items, one for "Quit" and one for displaying an "About" window. These handlers should not be virtual.

class MyFrame: public wxFrame
{
public:

    MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size);

    void OnQuit(wxCommandEvent& event);
    void OnAbout(wxCommandEvent& event);

    DECLARE_EVENT_TABLE()
};

In order to be able to react to a menu command, it must be given a unique identifier such as a const or an enum.

enum
{
    ID_Quit = 1,
    ID_About,
};

We then procede to actually implement an event table in which the events are routed to their respective handler functions in the class MyFrame. There are predefined macros for routing all common events, ranging from the selection of a list box entry to a resize event when a user resizes a window on the screen.

BEGIN_EVENT_TABLE(MyFrame, wxFrame)
    EVT_MENU(ID_Quit,  MyFrame::OnQuit)
    EVT_MENU(ID_About, MyFrame::OnAbout)
END_EVENT_TABLE()

As in all programs there must be a "main" function. Under wxWidgets main is implemented using this macro, which creates an application instance and starts the program.

IMPLEMENT_APP(MyApp)

As mentionend above, wxApp::OnInit() is called upon startup and should be used to initialize the program, maybe showing a "splash screen" and creating the main window (or several). The frame should get a title bar text ("Hello World") and a position and start-up size. One frame can also be declared to be the top window. Returning TRUE indicates a successful intialization.

bool MyApp::OnInit()
{
    MyFrame *frame = new MyFrame( _("Hello World"), wxPoint(50, 50), wxSize(450, 340) );
    frame->Show(true);
    SetTopWindow(frame);
    return true;
}

In the constructor of the main window (or later on) we create a menu with two menu items as well as a status bar to be shown at the bottom of the main window. Both have to be "announced" to the frame with respective calls.

MyFrame::MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size)
       : wxFrame(NULL, -1, title, pos, size)
{
    wxMenu *menuFile = new wxMenu;

    menuFile->Append( ID_About, _("&About...") );
    menuFile->AppendSeparator();
    menuFile->Append( ID_Quit, _("E&xit") );

    wxMenuBar *menuBar = new wxMenuBar;
    menuBar->Append( menuFile, _("&File") );

    SetMenuBar( menuBar );

    CreateStatusBar();
    SetStatusText( _("Welcome to wxWidgets!") );
}

Here are the actual event handlers. MyFrame::OnQuit() closes the main window by calling Close(). The paramter TRUE indicates that other windows have no veto power such as after asking "Do you really want to close?". If there is no other main window left, the applicatin will quit.

void MyFrame::OnQuit(wxCommandEvent& WXUNUSED(event))
{
    Close(true);
}

MyFrame::OnAbout() will display a small window with some text in it. In this case a typical "About" window with information about the program.

void MyFrame::OnAbout(wxCommandEvent& WXUNUSED(event))
{
    wxMessageBox( _("This is a wxWidgets Hello world sample"),
                  _("About Hello World"),
                  wxOK | wxICON_INFORMATION, this );
}

Under Unix (including Linux and OS X and nearly any system that uses GCC), you can use the following statement to compile the program:

g++ hworld.cpp `wx-config --libs` `wx-config --cxxflags` -o hworld

Finally, you might want to start the program with:

./hworld

A version of hello world using Connect() instead of event tables is here

引出出处:http://www.wxwidgets.org/docs/tutorials/hello.htm