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如何检测我的应用程序在Qt中失去焦点？

[英]How to detect that my application lost focus in Qt?

原文 2013-01-03 21:11:15 5 1 c++/ qt/ qt4/ qt5/ qevent

I'm displaying a popup window when the mouse cursor is over a certain widget and I'd like to hide this popup when the mouse leaves the widget. 当鼠标光标在某个小部件上时，我正在显示一个弹出窗口，我想在鼠标离开小部件时隐藏这个弹出窗口。

To do it, I reimplemented leaveEvent() . 为此，我重新实现了leaveEvent() 。 This seems to work in all cases except when switching to another application by Alt+Tab . 这似乎适用于所有情况，除非通过Alt+Tab切换到另一个应用程序。 I figured out that I probably need to catch another event, but somehow I can't find the proper one. 我发现我可能需要抓住另一个事件，但不知怎的，我找不到合适的事件。 Can you suggest one? 你能建议吗？

1 个解决方案

The event you are looking for is QEvent::ApplicationDeactivate : "The application has been suspended, and is unavailable to the user". 您正在寻找的事件是QEvent::ApplicationDeactivate ：“应用程序已被暂停，并且对用户不可用”。

You can install an event filter on your QApplication instance to catch this event. 您可以在QApplication实例上安装事件过滤器以捕获此事件。 See the documentation for QObject::installEventFilter(QObject*) for more details how this works. 有关其工作原理的更多详细信息，请参阅QObject::installEventFilter(QObject*)的文档。

Since Qt 5.2 the QEvent::ApplicationDeactivate event is deprecated. 从Qt 5.2开始，不推荐使用QEvent::ApplicationDeactivate事件。 The correct way to identify when an application is deactivated in Qt 5.2 (or later) is to use the QGuiApplication::applicationStateChanged(Qt::ApplicationState state) signal. 在Qt 5.2（或更高版本）中识别应用程序何时停用的正确方法是使用QGuiApplication::applicationStateChanged(Qt::ApplicationState state)信号。