Qt 急求回答

[qq_34480269]

MyLineEdit::MyLineEdit(QWidget *parent) :
QLineEdit(parent)
{
}

void MyLineEdit::keyPressEvent(QKeyEvent *event)
{
qDebug() << tr("MyLineEdit 键盘按下事件");
QLineEdit::keyPressEvent(event);
event->ignore();
}

void MyLineEdit::mousePressEvent(QMouseEvent *event)
{
qDebug() << "yyyy";
}

bool MyLineEdit::event(QEvent *event)
{
if(event->type() == QEvent::KeyPress) {
qDebug() << "xxxx";
QKeyEvent *ev = static_cast<QKeyEvent *>(event);
QLineEdit::keyPressEvent(ev);
return true;
}
//QObject::children();
return QLineEdit::event(event); // 为什么当我单机鼠标后还会输出“yyyy”。即我调用的明明是基类QLineEdit的event函数，而它却 不调用基类QLineEdit的mousePressEvent函数（因为我F11单步进入后qDebug() << "aaaa";），反而调用派生类的mousePressEvent而输出“yyyy”。
}

[stherix]

keyPress和mousePress是两回事啊

[qq_34480269]

引用 1 楼 stherix 的回复:

keyPress和mousePress是两回事啊

我知道，我的意思是在我实现的event函数中只对keyPress事件感兴趣并return true，但是当来一个mousePress事件时我直接return了父类的event函数。这个父类的event怎么可能调用子类的mousePressEvent（）事件处理函数呢？这个父类QLineEdit的event函数不应该也调用（父类即）QLineEdit的mousePressEvent（）么？

[弓人水]

QLineEdit::event(event)为什么会执行派生类的mousePressEvent？
因为类似mousePressEvent这些虚函数都会在QLineEdit的基类QWidget中的event方法中被调用。
相当于event会分发mousePressEvent这些子事件。
看下QWidget的event方法源码片段，基本就能理解了：

bool QWidget::event(QEvent *event)
{
    Q_D(QWidget);

    // ignore mouse and key events when disabled
    if (!isEnabled()) {
        switch(event->type()) {
        case QEvent::TabletPress:
        case QEvent::TabletRelease:
        case QEvent::TabletMove:
        case QEvent::MouseButtonPress:
        case QEvent::MouseButtonRelease:
        case QEvent::MouseButtonDblClick:
        case QEvent::MouseMove:
        case QEvent::TouchBegin:
        case QEvent::TouchUpdate:
        case QEvent::TouchEnd:
        case QEvent::TouchCancel:
        case QEvent::ContextMenu:
        case QEvent::KeyPress:
        case QEvent::KeyRelease:
#ifndef QT_NO_WHEELEVENT
        case QEvent::Wheel:
#endif
            return false;
        default:
            break;
        }
    }
    switch (event->type()) {
    case QEvent::MouseMove:
        mouseMoveEvent((QMouseEvent*)event);
        break;

    case QEvent::MouseButtonPress:
        mousePressEvent((QMouseEvent*)event);
        break;

    case QEvent::MouseButtonRelease:
        mouseReleaseEvent((QMouseEvent*)event);
        break;

    case QEvent::MouseButtonDblClick:
        mouseDoubleCl

[弓人水]

如果你想阻断事件的分发，可以在event方法里面return true。

bool MyLineEdit::event(QEvent *event)
{
    switch (event->type()) {
    case QEvent::KeyPress:
        qDebug() << "xxxx";
        QKeyEvent *ev = static_cast<QKeyEvent *>(event);
        QLineEdit::keyPressEvent(ev);
        return true;
        
    case QEvent::MouseButtonPress:
        return true; // 只会拦截MouseButtonPress事件（mousePressEvent虚函数不会被调用）

    return QLineEdit::event(event); // 如果把这里换成return true；则只会执行上面switch那些事件，其他事件都会被拦截

[stherix]

父类的event里不是必须调用自己类的mousePressEvent啊 因为你没有定义 所以他执行的还是event的默认实现,就是去找各个事件的实现 而因为多态的关系,这时候控件指针还是指向MyLineEdit的,最终还是执行了MyLineEdit的mousePressEvent