Qt的MDI中多个子窗口响应一个菜单事件的优雅实现(动态slot)
问题:
用过MFC的人都知道,MDI中,某个菜单或者按钮,在视图中可以添加响应函数,在文档中也可以添加响应函数,在框架中也可以添加它的响应函数,优先级分别是视图、文档、框架,而且MFC自动将消息发给当前激活的视图或者文档。
解决思路:
在Qt中,菜单/按钮的响应是通过信号/槽来实现的,在MDI中,多个视图经常需要响应同一个菜单,且是激活的视图去响应,这有两种处理方法,一 是,由主窗口接收事件再转调用当前激活窗口,二是,通过disconnect/connect动态修改信号槽。第一种方法,当这样的菜单事件比较多时,比 较繁琐;如果多个视图分属不同子类,只要其中一个子类实现了一个处理函数,其他子类都需要添加这样的处理函数(即使啥也不干),另外,在主窗口转调用时, 还需要做类型转换(或者通过虚函数),总而言之,比较复杂。
这里,我按照第二种方法,通过少量代码实现了动态修改信号槽。思路是:
1、自定义一个结构,将connect信息保存起来;
2、当MDI的子窗口焦点切换时,将connect信息中的receiver全部换成当前窗口,并重新connect;
该方法只需要在mainwindow中做这些工作即可,比较简洁优雅。
关键代码粘贴如下
class MainWindow : public QMainWindow
{
//......
void dynamic_connect(const QObject * sender, const char * signal, const QObject * receiver, const char * method);
void set_dynamic_connect_receiver(const QObject * receiver);
//......
struct MdiConnectInfo
{
MdiConnectInfo(const QObject * sender1, const char * signal1, const QObject * receiver1, const char * method1)
{
sender = sender1;
strcpy(signal,signal1);
receiver = receiver1;
strcpy(method, method1);
}
const QObject * sender;
char signal[100];
const QObject * receiver;
char method[100];
};
std::vector<MdiConnectInfo> m_mdiConnects;
};
MainWindow::MainWindow()
{
//......
connect(mdiArea, SIGNAL(subWindowActivated(QMdiSubWindow*)),
this, SLOT(onMdiActived()));
//......
}
void MainWindow::dynamic_connect(const QObject * sender, const char * signal, const QObject * receiver, const char * method)
{
m_mdiConnects.push_back(MdiConnectInfo(sender, signal, receiver, method));
}
void MainWindow::set_dynamic_connect_receiver(const QObject * receiver)
{
for (int i = 0; i < m_mdiConnects.size(); i++)
{
MdiConnectInfo item = m_mdiConnects[i];
disconnect(item.sender, item.signal, item.receiver, item.method);
}
for (int i = 0; i < m_mdiConnects.size(); i++)
{
MdiConnectInfo item = m_mdiConnects[i];
connect(item.sender, item.signal, receiver, item.method);
m_mdiConnects[i].receiver = receiver;
}
}
void MainWindow::onMdiActived()
{
QWidget* child = activeMdiChild();
if (child)
{
set_dynamic_connect_receiver(child);
}
}
void MainWindow::createActions()
{
//......
zoomInAct = new QAction(QIcon(":/images/zoomIn.png"), tr("Zoom In"), this);
zoomInAct->setStatusTip(tr("Zoom in view"));
dynamic_connect(zoomInAct, SIGNAL(triggered()), this, SLOT(zoomInView()));
zoomOutAct = new QAction(QIcon(":/images/zoomOut.png"), tr("Zoom Out"), this);
zoomOutAct->setStatusTip(tr("Zoom out view"));
dynamic_connect(zoomOutAct, SIGNAL(triggered()), this, SLOT(zoomOutView()));
zoomFitAct = new QAction(QIcon(":/images/zoomFit.png"), tr("Zoom Fit"), this);
zoomFitAct->setStatusTip(tr("Zoom fit view"));
dynamic_connect(zoomFitAct, SIGNAL(triggered()), this, SLOT(zoomFitView()));
zoomPanAct = new QAction(QIcon(":/images/zoomPan.png"), tr("Pan Zoom"), this);
zoomPanAct->setStatusTip(tr("Pan zoom view"));
dynamic_connect(zoomPanAct, SIGNAL(triggered()), this, SLOT(zoomPanView()));
//......
}
作一下解释:
1、通过MdiConnectInfo结构和m_mdiConnects变量,将connect信息保存起来;具体是通过函数dynamic_connect来完成的;
2、当MDI的子窗口焦点切换时,其响应函数onMdiActived()中,将connect信息中的receiver全部换掉,具体是通过 set_dynamic_connect_receiver来完成的;
上述代码运行正常。