第11章 GUI Page400~402 步骤二 画直线

运行效果：

源代码：

/***************************************************************
 * Name:      wxMyPainterApp.h
 * Purpose:   Defines Application Class
 * Author:    yanzhenxi (3065598272@qq.com)
 * Created:   2023-12-21
 * Copyright: yanzhenxi ()
 * License:
 **************************************************************/

#ifndef WXMYPAINTERAPP_H
#define WXMYPAINTERAPP_H

#include <wx/app.h>

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

#endif // WXMYPAINTERAPP_H

/***************************************************************
 * Name:      wxMyPainterApp.cpp
 * Purpose:   Code for Application Class
 * Author:    yanzhenxi (3065598272@qq.com)
 * Created:   2023-12-21
 * Copyright: yanzhenxi ()
 * License:
 **************************************************************/

#include "wxMyPainterApp.h"

//(*AppHeaders
#include "wxMyPainterMain.h"
#include <wx/image.h>
//*)

IMPLEMENT_APP(wxMyPainterApp);

bool wxMyPainterApp::OnInit()
{
    //(*AppInitialize
    bool wxsOK = true;
    wxInitAllImageHandlers();
    if ( wxsOK )
    {
    	wxMyPainterFrame* Frame = new wxMyPainterFrame(0);
    	Frame->Show();
    	SetTopWindow(Frame);
    }
    //*)
    return wxsOK;

}

/***************************************************************
 * Name:      wxMyPainterMain.h
 * Purpose:   Defines Application Frame
 * Author:    yanzhenxi (3065598272@qq.com)
 * Created:   2023-12-21
 * Copyright: yanzhenxi ()
 * License:
 **************************************************************/

#ifndef WXMYPAINTERMAIN_H
#define WXMYPAINTERMAIN_H

//(*Headers(wxMyPainterFrame)
#include <wx/scrolwin.h>
#include <wx/sizer.h>
#include <wx/menu.h>
#include <wx/listbox.h>
#include <wx/frame.h>
#include <wx/statusbr.h>
//*)

class wxMyPainterFrame: public wxFrame
{
    public:

        wxMyPainterFrame(wxWindow* parent,wxWindowID id = -1);
        virtual ~wxMyPainterFrame();

    private:

        //(*Handlers(wxMyPainterFrame)
        void OnQuit(wxCommandEvent& event);
        void OnAbout(wxCommandEvent& event);
        void OnScrolledWindow1LeftDown(wxMouseEvent& event);
        void OnScrolledWindow1MouseMove(wxMouseEvent& event);
        void OnScrolledWindow1LeftUp(wxMouseEvent& event);
        void OnScrolledWindow1Paint(wxPaintEvent& event);
        //*)

        //(*Identifiers(wxMyPainterFrame)
        static const long ID_LISTBOX1;
        static const long ID_SCROLLEDWINDOW1;
        static const long idMenuQuit;
        static const long idMenuAbout;
        static const long ID_STATUSBAR1;
        //*)

        //(*Declarations(wxMyPainterFrame)
        wxScrolledWindow* ScrolledWindow1;
        wxStatusBar* StatusBar1;
        wxListBox* ListBox1;
        //*)

    private:
        bool _drawing; //绘图状态：真则表示正在绘图
        wxPoint _startPosition, _currentPosition; //正在画的图形的开始位置和最新位置

        DECLARE_EVENT_TABLE()
};

#endif // WXMYPAINTERMAIN_H

/***************************************************************
 * Name:      wxMyPainterMain.cpp
 * Purpose:   Code for Application Frame
 * Author:    yanzhenxi (3065598272@qq.com)
 * Created:   2023-12-21
 * Copyright: yanzhenxi ()
 * License:
 **************************************************************/

#include "wxMyPainterMain.h"
#include <wx/msgdlg.h>
#include <wx/dcclient.h>

//(*InternalHeaders(wxMyPainterFrame)
#include <wx/settings.h>
#include <wx/intl.h>
#include <wx/string.h>
//*)

//helper functions
enum wxbuildinfoformat {
    short_f, long_f };

wxString wxbuildinfo(wxbuildinfoformat format)
{
    wxString wxbuild(wxVERSION_STRING);

    if (format == long_f )
    {
#if defined(__WXMSW__)
        wxbuild << _T("-Windows");
#elif defined(__UNIX__)
        wxbuild << _T("-Linux");
#endif

#if wxUSE_UNICODE
        wxbuild << _T("-Unicode build");
#else
        wxbuild << _T("-ANSI build");
#endif // wxUSE_UNICODE
    }

    return wxbuild;
}

//(*IdInit(wxMyPainterFrame)
const long wxMyPainterFrame::ID_LISTBOX1 = wxNewId();
const long wxMyPainterFrame::ID_SCROLLEDWINDOW1 = wxNewId();
const long wxMyPainterFrame::idMenuQuit = wxNewId();
const long wxMyPainterFrame::idMenuAbout = wxNewId();
const long wxMyPainterFrame::ID_STATUSBAR1 = wxNewId();
//*)

BEGIN_EVENT_TABLE(wxMyPainterFrame,wxFrame)
    //(*EventTable(wxMyPainterFrame)
    //*)
END_EVENT_TABLE()

wxMyPainterFrame::wxMyPainterFrame(wxWindow* parent,wxWindowID id)
    : _drawing(false), _startPosition(0, 0), _currentPosition(0, 0)
{
    //(*Initialize(wxMyPainterFrame)
    wxMenuItem* MenuItem2;
    wxMenuItem* MenuItem1;
    wxMenu* Menu1;
    wxBoxSizer* BoxSizer1;
    wxMenuBar* MenuBar1;
    wxMenu* Menu2;

    Create(parent, id, wxEmptyString, wxDefaultPosition, wxDefaultSize, wxDEFAULT_FRAME_STYLE, _T("id"));
    SetClientSize(wxSize(208,94));
    BoxSizer1 = new wxBoxSizer(wxHORIZONTAL);
    ListBox1 = new wxListBox(this, ID_LISTBOX1, wxDefaultPosition, wxSize(168,68), 0, 0, 0, wxDefaultValidator, _T("ID_LISTBOX1"));
    BoxSizer1->Add(ListBox1, 0, wxALL|wxEXPAND, 5);
    ScrolledWindow1 = new wxScrolledWindow(this, ID_SCROLLEDWINDOW1, wxDefaultPosition, wxDefaultSize, wxVSCROLL|wxHSCROLL, _T("ID_SCROLLEDWINDOW1"));
    ScrolledWindow1->SetBackgroundColour(wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOW));
    BoxSizer1->Add(ScrolledWindow1, 1, wxALL|wxEXPAND, 5);
    SetSizer(BoxSizer1);
    MenuBar1 = new wxMenuBar();
    Menu1 = new wxMenu();
    MenuItem1 = new wxMenuItem(Menu1, idMenuQuit, _("Quit\tAlt-F4"), _("Quit the application"), wxITEM_NORMAL);
    Menu1->Append(MenuItem1);
    MenuBar1->Append(Menu1, _("&File"));
    Menu2 = new wxMenu();
    MenuItem2 = new wxMenuItem(Menu2, idMenuAbout, _("About\tF1"), _("Show info about this application"), wxITEM_NORMAL);
    Menu2->Append(MenuItem2);
    MenuBar1->Append(Menu2, _("Help"));
    SetMenuBar(MenuBar1);
    StatusBar1 = new wxStatusBar(this, ID_STATUSBAR1, 0, _T("ID_STATUSBAR1"));
    int __wxStatusBarWidths_1[1] = { -1 };
    int __wxStatusBarStyles_1[1] = { wxSB_NORMAL };
    StatusBar1->SetFieldsCount(1,__wxStatusBarWidths_1);
    StatusBar1->SetStatusStyles(1,__wxStatusBarStyles_1);
    SetStatusBar(StatusBar1);
    SetSizer(BoxSizer1);
    Layout();

    ScrolledWindow1->Connect(wxEVT_PAINT,(wxObjectEventFunction)&wxMyPainterFrame::OnScrolledWindow1Paint,0,this);
    ScrolledWindow1->Connect(wxEVT_LEFT_DOWN,(wxObjectEventFunction)&wxMyPainterFrame::OnScrolledWindow1LeftDown,0,this);
    ScrolledWindow1->Connect(wxEVT_LEFT_UP,(wxObjectEventFunction)&wxMyPainterFrame::OnScrolledWindow1LeftUp,0,this);
    ScrolledWindow1->Connect(wxEVT_MOTION,(wxObjectEventFunction)&wxMyPainterFrame::OnScrolledWindow1MouseMove,0,this);
    Connect(idMenuQuit,wxEVT_COMMAND_MENU_SELECTED,(wxObjectEventFunction)&wxMyPainterFrame::OnQuit);
    Connect(idMenuAbout,wxEVT_COMMAND_MENU_SELECTED,(wxObjectEventFunction)&wxMyPainterFrame::OnAbout);
    //*)
}

wxMyPainterFrame::~wxMyPainterFrame()
{
    //(*Destroy(wxMyPainterFrame)
    //*)
}

void wxMyPainterFrame::OnQuit(wxCommandEvent& event)
{
    Close();
}

void wxMyPainterFrame::OnAbout(wxCommandEvent& event)
{
    wxString msg = wxbuildinfo(long_f);
    wxMessageBox(msg, _("Welcome to..."));
}

void wxMyPainterFrame::OnScrolledWindow1LeftDown(wxMouseEvent& event)
{
    /*若为真，表示此时正处于绘画转态，也就没有必要设置_drawing
    和取画图的其实点了，这种情况对应着，在画图中，按着左键拖动过程中*/
    if(_drawing)
    {
        return;
    }

    _drawing = true;
    _startPosition = event.GetPosition();
}

void wxMyPainterFrame::OnScrolledWindow1MouseMove(wxMouseEvent& event)
{
    if(!_drawing)//不在绘画状态？
    {
        return;//直接退出
    }

    _currentPosition = event.GetPosition();
    ScrolledWindow1->Refresh();
}

void wxMyPainterFrame::OnScrolledWindow1LeftUp(wxMouseEvent& event)
{
    if(!_drawing)//不在绘画状态？
    {
        return; //直接推出
    }

    _currentPosition = event.GetPosition();
    ScrolledWindow1->Refresh();

    _drawing = false; //结束绘画状态
}

void wxMyPainterFrame::OnScrolledWindow1Paint(wxPaintEvent& event)
{
    wxPaintDC dc(ScrolledWindow1);
    dc.DrawLine(_startPosition, _currentPosition);
}

关键代码：

增加私有成员数据

初始化成员数据

实现鼠标按下，移动，抬起三个函数

实现画图函数