一、QT打开指定网站和文件夹
在Qt程序中，如果要打开指定网站或系统中的文件夹，可以使用QDesktopServices类的openUrl方法。
详见http://qt-project.org/doc/qt-5/qdesktopservices.html
比如要打开Qt开发社区，相应的代码如下：
#include <QDesktopServices>
#include <QUrl>
QDesktopServices::openUrl(QUrl("http://qt-project.org/doc/qt-5/classes.html"));
要打开系统中的某个文件夹，如下：
[cpp] view plaincopy
QDesktopServices::openUrl(QUrl("file:///C:/Documents and Settings/All Users", QUrl::TolerantMode));
需要注意的是打开网址是http://，打开文件夹是file:///
在官网中关于QDesktopServices::openUrl的方法描述如下：
bool QDesktopServices::openUrl(constQUrl & url) [static]
Opens the given url in the appropriate Web browser for the user's desktop environment, and returnstrue if successful; otherwise returnsfalse.
If the URL is a reference to a local file (i.e., the URL scheme is "file") then it will be opened with a suitable application instead of a Web browser.
The following example opens a file on the Windows file system residing on a path that contains spaces:
QDesktopServices::openUrl(QUrl("file:///C:/Documents and Settings/All Users/Desktop", QUrl::TolerantMode));
二、Qt中QUrl::addQueryItem的Bug
在开发中，用到了如下语句：
QUrl url = QString("http://localhost/test")
url.addQueryItem("test", QString("abc+bcd"));
服务器一收，发现接收到的字符串变成了"abc bcd"。顿时郁闷了。
查了半天，找不着原因，上论坛问，很久也没人回答。
终于，有一位大牛解开了疑惑：
Qt should be encoding the literal '+' as %2B on your behalf. There is a bug that has been (I think incorrectly) closed as invalid:http://bugreports.qt.nokia.com/browse/QTBUG-10146
You can work around it with this:
Qt Code:Switch viewurl.addEncodedQueryItem("another",QUrl::toPercentEncoding("abc+bcd"));
最后，推荐一个Qt论坛，牛人挺多的。
