Mouse events

Mouse events include mouse movement, mouse button press, release, click, and double-click.
Include header file when using < qmouseevent >
The mouse movement event response is realized by redefining mouseMoveEvent(QMouseEvent *e) function

e->x();e->y(); // Get the relative position of the mouse  

The mouse press event response is realized by redefining the mousePressEvent(QMouseEvent *e) function

if(e->button()==Qt::LeftButton)   // Qt::RightButton right click Qt::MidButton middle key
{
    statusBar()->showMessage(tr("Left key:")+str);
}

The mouse release event response is implemented by redefining the mouserelease event (qmouseevent * e) function
The mouse double click event response is realized by redefining mouseDoubleClickEvent(QMouseEvent *e) function
This - > setmousetracking (true); / / form tracking mouse. True is tracking, false is not tracking

Keyboard events

When using, include the header file < qkeyevent >
Implemented by redefining keyPressEvent(QKeyEvent *) and keyReleaseEvent(QKeyEvent *)

// QT:: a series of modifier keys defined by keyboardmodifier
// Qt::ControlModifier [Ctrl]
// Qt::NoModifier has no modifier key
// Qt::AltModifier [Alt] key
// QT:: metamodifier meta key, usually available on Linux keyboard
// Qt::KeypadModifier keypad key

if(event->modifiers()==Qt::ControlModifier)
{
    if(event->key()==Qt::Key_Left)                            // Assembly Ctrl left key combination
    {
    }
}
else								//Processing of not pressing the Ctrl key
{
    if(event->key()==Qt::Key_Left)	
    {
    }
}

Event filtering
Main function, function prototype

void QObject::installEventFilter(QObject * filterObj);// Add event filter

void QObject::removeEventFilter(QObject * filterObj); // Remove event filtering

bool eventFilter(QObject *watched, QEvent *event);    // Event filter function. If it is filtered, it returns true; otherwise, it returns false

Example

// Add filter event
label1->installEventFilter(this);
label2->installEventFilter(this);
label3->installEventFilter(this);

// Event filter function
bool EventFilter::eventFilter(QObject *watched, QEvent *event)
{
    if(watched==label1)			//First, judge the object of the current event
    {
        // Determine the type of event
        if(event->type()==QEvent::MouseButtonPress)
        {
            // Convert event to mouse event
            QMouseEvent *mouseEvent=(QMouseEvent *)event;
            /* The following are displayed according to the key type of the mouse */
            if(mouseEvent->buttons()&Qt::LeftButton)
            {
                stateLabel->setText(tr("Left click to press the left picture"));
            }
            else if(mouseEvent->buttons()&Qt::MidButton)
            {
                stateLabel->setText(tr("Middle press the left picture"));
            }
            else if(mouseEvent->buttons()&Qt::RightButton)
            {
                stateLabel->setText(tr("Right click the left picture"));
            }
            /* Show zoomed out pictures */
            QMatrix matrix;
            matrix.scale(1.8,1.8);
            QImage tmpImg=Image1.transformed(matrix);
            label1->setPixmap(QPixmap::fromImage(tmpImg));
        }
        /* Handle the mouse release event and restore the size of the picture */
        if(event->type()==QEvent::MouseButtonRelease)
        {
            stateLabel->setText(tr("Mouse release left picture"));
            label1->setPixmap(QPixmap::fromImage(Image1));
        }
    }
    ......
}