QPropertyAnimation for rotating QWidget

问题

I'm new to Qt and I'm having some problem with QWidget rotation.

I have a QPixmap inside a QLabel. What I want is to animate it with a continuous rotation by 90 degrees.

I know QPropertyAnimation and I know how to use it, but I'm struggling with How to use it for rotating a QWidget. Is there any simple way to use achieve my goal and rotate the entire QLabel or the QPixmap inside it with an animation? Thank you.

回答1:

This is the demo for rotation of QLabel/QPixmap with animation. it's not necessary to use QPropertyAnimation. Because there is no rotate property for QLabel or QPixmap. So used QVariantAnimation make QPixmap rotate as animation and use QPixmap::transformed to rotate it. If you want well to control the animation of the pixmap, highly recommend QGraphicsPixmapItem with QPropertyAnimation

class RotateMe : public QLabel {

    Q_OBJECT
public:
    explicit RotateMe(QWidget* parent = Q_NULLPTR) :
        QLabel(parent),
        pixmap(100, 100),
        animation(new QVariantAnimation )
    {
        resize(200, 200);
        pixmap.fill(Qt::red);

        animation->setDuration(10000);
        animation->setStartValue(0.0f);
        animation->setEndValue(90.0f);
        connect(animation, &QVariantAnimation::valueChanged, [=](const QVariant &value){
            qDebug()<<value;
            QTransform t;
            t.rotate(value.toReal());
            setPixmap(pixmap.transformed(t));
        });
        animation->start();
    }
private:
    QPixmap             pixmap;
    QVariantAnimation  *animation;
};

回答2:

You can implement the rotation in two ways:

1) Create a collection of static images each of which represents the original pixmap rotated by some angle. With a timer you can change your label's pixmap with one from your collection. This will imitate the animated rotation.

2) Use a single pixmap and override your label's QLabel::painEvent() where you should rotate the QPainter object with QPainter::rotate() function each time you redraw the label.

来源：https://stackoverflow.com/questions/50286919/qpropertyanimation-for-rotating-qwidget