c++ - Qt事件过滤器隐藏widget

Question

我有一个父小部件，我必须在其中放置一个自定义小部件(比如 QFrame)。在该自定义小部件中，我必须放置一些子小部件(派生自 QPushButton)。我希望子部件在正常情况下具有特定的背景，而在悬停时具有另一个背景。这是我的代码:

//parent widget code, where the QFrame derived widget is initialized
QFrameDerivedWidget *qFrameWidget = new QFrameDerivedWidget(this, someString);

这是QFrameDerivedWidget头文件:

//QFrameDerivedWidget header file
class QFrameDerivedWidget: public QFrame
{
    Q_OBJECT

public:
    QFrameDerivedWidget(QWidget *aParent,
                         std::string someValue);
    bool eventFilter(QObject *obj, QEvent *event);
}

这是QFrameDerivedWidget实现文件，ChildWidget类被定义并内联声明:

class ChildWidget: public QPushButton
{
Q_Object
public:
    ChildWidget(std::string aText, QWidget *aParent);

};

ChildWidget::ChildWidget(std::string aText, QWidget *aParent):
                               QPushButton(QString::fromStdString(aText),aParent)
{
    this->setFixedHeight(30);
    this->setMouseTracking(true);
    this->setCursor(Qt::PointingHandCursor);
    /* ---other custom styling--- */
}

bool QFrameDerivedWidget::eventFilter(QObject *obj, QEvent *event)
{
    // this never prints out anything, even though it should for any mouseenter, mouseleave, click, etc event on it
    qDebug() << obj->metaObject()->className() << endl;

    if (obj->metaObject()->className() == "ChildWidget")
    {
        //including this line throws a 'missing QObject missing macro error' as well
        ChildWidget *option = qobject_cast<ChildWidget* >(obj);
        if (event->type() == QEvent::Enter)
        {
            option->setStyleSheet("---");

        }
        if (event->type() == QEvent::Leave)
        {
            option->setStyleSheet("---");
        }
        return QWidget::eventFilter(obj, event);
    }
    else
    {
        // pass the event on to the parent class
        return QWidget::eventFilter(obj, event);
    }
}

QFrameDerivedWidget::QFrameDerivedWidget(QWidget *aParent,
                     std::string someVal): fParent(aParent)
{
    initUI();
}

QFrameDerivedWidget::initUI()
{
    this->setParent(fParent);
    this->setAttribute(Qt::WA_Hover);
    this->setMouseTracking(true);
    QWidget *dd = new QWidget(this);
    QVBoxLayout *layout = new QVBoxLayout();
    dd->setLayout(layout);
    for (int i = 0; i < fValues.size(); i++)
    {
        ChildWidget *button = new ChildWidget(fValues[i],dd);
        button->addEventFilter(this);
        layout->addWidget(button);
    }
}

想法是，每当我将鼠标悬停在 QFrameDerivedWidget 上并输入任何 ChildWidget 时，它的背景颜色都应该改变。此外，我在 eventFilter 中设置了一个 qDebug() 语句。它目前不工作，ChildWidget 按钮不可见，但它们在那里，因为当我将鼠标悬停在它们应该在的位置上时，光标会变成指针。

我做错了什么，我该如何让它发挥作用？

Answer 1

1. 您忘记在 ChildWidget 声明中添加 Q_OBJECT 宏
2. 您需要跟踪鼠标 (setMouseTracking(true))
3. 您需要为您的小部件设置setAttribute(Qt::WA_Hover)
4. 确保您确实需要在事件过滤器中return true;，而不是返回QWidget::eventFilter(obj, event);。您不需要过滤掉悬停事件。