QKeyEvent奇怪的现象
我用消息过滤器响应按键消息

bool CMainWindow::eventFilter(QObject *target, QEvent *event)
{
    if(QEvent::KeyPress == event->type())
    {
        std::cout<<"press"<<std::endl;
        return true;
    }
    else if(QEvent::KeyRelease == event->type())
   {
         std::cout<<"release"<<std::endl;
         return;
    }
    return false;
}

我按着一个键不动结果显示

press
release
press
release
press
release
press
release
press
release
我根本就没有松开，为什么会不停的press，release。MFC里面不会，应该不是我键盘问题吧。 Qt QKeyEvent 消息过滤 多个按键
[解决办法]
刚看了下源码。

qkeymaper_win.cpp里面

            // If we have a record, it means that the key is already pressed, the state is the same
            // so, we have an auto-repeating key
            if (rec) {
                if (code < Qt::Key_Shift 
[解决办法]
 code > Qt::Key_ScrollLock) {
                    k0 = q->sendKeyEvent(widget, grab, QEvent::KeyRelease, code,
                                         Qt::KeyboardModifier(state), rec->text, true, 0,
                                         scancode, msg.wParam, nModifiers);
                    k1 = q->sendKeyEvent(widget, grab, QEvent::KeyPress, code,
                                         Qt::KeyboardModifier(state), rec->text, true, 0,
                                         scancode, msg.wParam, nModifiers);
                }
            }

注释告诉我们，Qt的行为是这样的，你也看到了他发送了2个事件 k0 keyrelease. k1 keypress.
所以能收到2个。

解决方法：通过QKeyEvent::isAutoRepeat() 来判断。

bool Widget::eventFilter(QObject *obj, QEvent *event)
{
    if(QEvent::KeyPress == event->type())
    {
        QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
        qDebug()<<"press event" <<keyEvent->isAutoRepeat();
        return true;
    }
    else if(QEvent::KeyRelease == event->type())
    {
         QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
         qDebug() <<"release event" << keyEvent->isAutoRepeat();
         return true;
    }
    return false;
}