windows 查找单实例Qt应用程序的QWidget
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Find QWidget of single instance Qt application
提问by corné
I'm trying to create a single instance Qt application and I'm at the point this works, but now I want to focus the already started instance when a second is started. QWidget::find(g_hWnd) should return the widget but it fails and crashes on w->show();
我正在尝试创建一个单实例 Qt 应用程序，我现在可以使用了，但是现在我想在启动第二个实例时关注已经启动的实例。QWidget::find(g_hWnd) 应该返回小部件，但它在 w->show() 上失败并崩溃；
Any thoughts?
有什么想法吗？
#pragma data_seg("Shared")
HWND g_hWnd = NULL;
#pragma data_seg()
#pragma comment(linker,"/section:Shared,rws")
int main(int argc, char *argv[])
{
if (g_hWnd)
{
QWidget* w = QWidget::find(g_hWnd);
w->show();
return 0;
}
else
{
QApplication a(argc, argv);
mainWindow w;
w.show();
g_hWnd = a.topLevelWidgets().at(0)->winId(); //or w.winId()?
return a.exec();
}
}
edit: I now see Trolltech released the QtSingleApplicationclass under LGPL.
编辑：我现在看到奇趣科技在 LGPL 下发布了QtSingleApplication类。
回答by Martin Beckett
You should use the qtsingleapplicationAPI
您应该使用qtsingleapplicationAPI
edit- It's a separate download see herefor both LGPL and Commercial editions
编辑 - LGPL 和商业版本的单独下载 请参见此处
回答by Balkrishna Talele
#include <QtGui/QApplication>
#include "mainwindow.h"
#include <QMessageBox>
#include <QSharedMemory>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
QSharedMemory shared("61BB200D-3579-453e-9044-");
if(shared.create(512,QSharedMemory::ReadWrite)==true)
{
QMessageBox msgBox;
msgBox.setText("I am first.");
msgBox.exec();
}
else
{
QMessageBox msgBox;
msgBox.setText("i am already running.");
msgBox.exec();
exit(0);
}
//shared.AlreadyExists()
w.show();
return a.exec();
}
回答by Balkrishna Talele
This could be the problem you're having:
这可能是您遇到的问题：
WId QWidget::winId () const
Returns the window system identifier of the widget.
Portable in principle, but if you use it you are probably about to do something non-portable. Be careful.
If a widget is non-native (alien) and winId() is invoked on it, that widget will be provided a native handle.
Note: We recommend that you do not store this value as it is likely to change at run-time.
WId QWidget::winId () const
返回小部件的窗口系统标识符。
原则上是可移植的，但如果你使用它，你可能会做一些不可移植的事情。当心。
如果小部件是非本地的（外来的）并且在其上调用了 winId()，则将为该小部件提供一个本地句柄。
注意：我们建议您不要存储此值，因为它可能会在运行时更改。
回答by Ariya Hidayat
I doubt your method is going to work.
我怀疑你的方法会奏效。
The best approach is still by running a local server (see QLocalServer) that listens from a specific socket. An newly launched instance will detect the running server and can pipe agreed command to e.g. set the focus, open a new file, etc.
最好的方法仍然是运行从特定套接字侦听的本地服务器（请参阅QLocalServer）。新启动的实例将检测正在运行的服务器，并可以通过管道传输同意的命令，例如设置焦点、打开新文件等。
A similar approach is to use named shared memory (see QSharedMemory). Same like before, if the shared memory exists already, the other side can control it by sending suitable commands.
类似的方法是使用命名共享内存（请参阅QSharedMemory）。和之前一样，如果共享内存已经存在，对方可以通过发送合适的命令来控制它。
