在项目中需要用到程序更新的功能,同事介绍说是curl中的开发库很不错,于是下载这个包测试了一下，确实不错。准备正式用到项目中，以下一个例子用于从互联网上抓取一个文件下载到本地，并加上进度条显示，做得挺简陋，不过功能差不多就这样了。

程序运行预览.

首先需要加入多线程的机制，因为程序一边在下载文件，一边在显示进度条，单线程的方式肯定不行，所以我用到了wxTimer来实现,在downloadMain.h 中定义了一个wxTimer，并做了事件申明.
DECLARE_EVENT_TABLE()

 

/*************************************************************** 
 * Name:            downloadMain.h 
 * Purpose:     Defines Application Frame 
 * Author:         () 
 * Created:     2008-11-14 
 * Copyright:    () 
 * License: 
 **************************************************************/ 
 
#ifndef DOWNLOADMAIN_H 
#define DOWNLOADMAIN_H 
 
 
 
#include "downloadApp.h" 
 
 
#include <wx/timer.h> 
#include "GUIDialog.h" 
 
class downloadDialog: public GUIDialog 
{ 
        public: 
                downloadDialog(wxDialog *dlg); 
                ~downloadDialog(); 
                void .Timer(wxTimerEvent& event); 
        private: 
                virtual void .Close(wxCloseEvent& event); 
                virtual void .Quit(wxCommandEvent& event); 
                virtual void .About(wxCommandEvent& event); 
                void downloadfile(); 
                wxTimer* m_timerdown; 
                DECLARE_EVENT_TABLE() 
}; 
#endif // DOWNLOADMAIN_H

下面是主程序的代码.

/*************************************************************** 
 * Name:            downloadMain.cpp 
 * Purpose:     Code for Application Frame 
 * Author:         (alan) 
 * Created:     2008-11-14 
 * License: 
 **************************************************************/ 
 
#ifdef WX_PRECOMP 
#include "wx_pch.h" 
#endif 
 
#ifdef __BORLANDC__ 
#pragma hdrstop 
#endif //__BORLANDC__ 
 
#include "downloadMain.h" 
#include <curl/curl.h> 
#include <curl/types.h> 
#include <curl/easy.h> 
#include "update.h" 
#include <wx/msgdlg.h> 
#include <wx/utils.h> 
#define TIMER_ID 22222 
//事件监听声明 
BEGIN_EVENT_TABLE(downloadDialog, GUIDialog) 
        EVT_TIMER(TIMER_ID, downloadDialog::OnTimer) 
END_EVENT_TABLE() 
 
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(__WXMAC__) 
                wxbuild << _T("-Mac"); 
#elif defined(__UNIX__) 
                wxbuild << _T("-Linux"); 
#endif 
 
#if wxUSE_UNICODE 
                wxbuild << _T("-Unicode build"); 
#else 
                wxbuild << _T("-ANSI build"); 
#endif // wxUSE_UNICODE 
        } 
 
        return wxbuild; 
} 
 
//声明一个文件结构体 
struct FtpFile 
{ 
        char *filename; 
        FILE *stream; 
}; 
 
downloadDialog::downloadDialog(wxDialog *dlg) 
                : GUIDialog(dlg) 
{ 
 
        //创建一个定时器,制定TIMER_ID 
        m_timerdown = new wxTimer(this, TIMER_ID); 
        //定时器开始运行,这里会自动执行OnTimer函数 
        m_timerdown->Start(100); 
} 
 
downloadDialog::~downloadDialog() 
{ 
 
} 
//定时器操作 
void downloadDialog::OnTimer(wxTimerEvent &event) 
{ 
        downloadfile(); 
} 
//文件写入流 
int my_fwrite(void *buffer, size_t size, size_t nmemb, void *stream) 
{ 
        struct FtpFile *out=(struct FtpFile *)stream; 
        if (out && !out->stream) 
        { 
                out->stream=fopen(out->filename, "wb"); 
                if (!out->stream) 
                { 
                        return -1; 
                } 
        } 
        return fwrite(buffer, size, nmemb, out->stream); 
} 
//进度条显示函数 
int wxcurldav_dl_progress_func(void* ptr, double rDlTotal, double rDlNow, double rUlTotal, double rUlNow) 
{ 
                                wxGauge* pGauge = (wxGauge*) ptr; 
                                if(pGauge) 
                                //设置进度条的值 
                                        pGauge->SetValue(100.0 * (rDlNow/rDlTotal)); 
                                return 0; 
} 
//下载文件函数 
void downloadDialog::downloadfile() 
{ 
        //创建curl对象 
        CURL *curl; 
        CURLcode res; 
        m_staticText2->SetLabel(wxT("请耐心等待程序下载更新包...")); 
        struct FtpFile ftpfile= 
        { 
                //定义下载到本地的文件位置和路径 
                "tmp.exe",NULL 
        }; 
        curl_global_init(CURL_GLOBAL_DEFAULT); 
 
        //curl初始化 
        curl = curl_easy_init(); 
 
        //curl对象存在的情况下执行操作 
        if (curl) 
        { 
                //设置远端地址 
                curl_easy_setopt(curl, CURLOPT_URL,"http://dl_dir.qq.com/minigamefile/QQGame2008ReleaseP2_web_setup.EXE"); 
                //执行写入文件流操作 
                curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, my_fwrite); 
                curl_easy_setopt(curl, CURLOPT_WRITEDATA, &ftpfile); 
                //curl的进度条声明 
                curl_easy_setopt(curl, CURLOPT_NOPROGRESS, FALSE); 
                //回调进度条函数 
                curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, wxcurldav_dl_progress_func); 
                //设置进度条名称 
                curl_easy_setopt(curl, CURLOPT_PROGRESSDATA, m_gauge1); 
 
                //进度条 
                m_gauge1->SetValue(0); 
                //写入文件 
                res = curl_easy_perform(curl); 
                m_gauge1->SetValue(100); 
                //释放curl对象 
                curl_easy_cleanup(curl); 
 
                if (CURLE_OK != res) 
                        ; 
        } 
        if (ftpfile.stream) 
        { 
                //关闭文件流 
                fclose(ftpfile.stream); 
        } 
                //释放全局curl对象 
                curl_global_cleanup(); 
                //这一步很重要，停止定时器,不然程序会无休止的运行下去 
                m_timerdown->Stop(); 
                //执行刚下载完毕的程序,进行程序更新 
                int pid = ::wxExecute(_T("tmp.exe")); 
                wxMessageBox(wxT("下载完毕，程序开始执行更新操作......")); 
} 
void downloadDialog::OnClose(wxCloseEvent &event) 
{ 
        Destroy(); 
} 
 
void downloadDialog::OnQuit(wxCommandEvent &event) 
{ 
        Destroy(); 
} 
 
void downloadDialog::OnAbout(wxCommandEvent &event) 
{ 
 
}