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?

问题描述

当鼠标光标悬停在某个小部件上时，我会显示一个弹出窗口，当鼠标离开该小部件时，我想隐藏此弹出窗口.

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.

为此，我重新实现了 leaveEvent().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.我发现我可能需要捕捉另一个事件，但不知何故我找不到合适的事件.你能推荐一个吗?

To do it, I reimplemented leaveEvent(). This seems to work in all cases except when switching to another application by Alt+Tab. I figured out that I probably need to catch another event, but somehow I can't find the proper one. Can you suggest one?

推荐答案

您要查找的事件是 QEvent::ApplicationDeactivate:应用程序已暂停，用户无法使用".

The event you are looking for is QEvent::ApplicationDeactivate: "The application has been suspended, and is unavailable to the user".

您可以在您的 QApplication 实例上安装一个事件过滤器来捕捉这个事件.请参阅QObject::installEventFilter(QObject*) 了解更多详情.

You can install an event filter on your QApplication instance to catch this event. See the documentation for QObject::installEventFilter(QObject*) for more details how this works.

自 Qt 5.2 起，QEvent::ApplicationDeactivate 事件已被弃用.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.

Since Qt 5.2 the QEvent::ApplicationDeactivate event is deprecated. 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.

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