QT event filter simple case

1、 Create a new one widget,ui The interface design is as follows

2、widget.h Add constructor to

bool eventFilter(QObject *watched, QEvent *event);

3、 stay widget.cpp Add the following code to

Add header file

#include <QKeyEvent>
#include <QWheelEvent>

Install the filter ：

ui->textEdit->installEventFilter(this);
ui->spinBox->installEventFilter(this);
ui->label->installEventFilter(this);

Add filter refactoring function ：

bool Widget::eventFilter(QObject *watched, QEvent *event)
{
    
    if(watched==ui->textEdit)
    {
    
        if(event->type()==QEvent::Wheel)
        {
    
            QWheelEvent *wheelEvent = (QWheelEvent*)event;
            if(wheelEvent->delta()>0)
                ui->textEdit->zoomIn();
            else
                ui->textEdit->zoomOut();
        }
    }
    else if(watched==ui->spinBox)
    {
    
        if(event->type()==QEvent::KeyPress)
        {
    
            QKeyEvent *keyEvent = (QKeyEvent*)event;
            if(keyEvent->key()==Qt::Key_Space)
                ui->spinBox->setValue(0);
        }
    }
    else if(watched==ui->label)
    {
    
        if(event->type()==QEvent::MouseButtonPress)
        {
    
            QMouseEvent *mouseEvent = (QMouseEvent*)event;
            if(mouseEvent->button()==Qt::LeftButton)
                ui->textEdit->setText(tr(" Left click on the picture ！"));
            else if(mouseEvent->button()==Qt::RightButton)
                ui->textEdit->setText(tr(" Right click on the picture ！"));
        }
    }
    else
        return QWidget::eventFilter(watched,event);
    return false;
}

4、 Run the project

Click the picture with the left mouse button

Right click on the picture

Mouse in textEdit Slide the roller up , Changed the font size