Qt-状态机

//以下示例是QT示例中的appchooser例子,使用状态机来进行图标的交互.

#include <QtCore>
#include <QtWidgets>


class Pixmap : public QGraphicsWidget
{
    Q_OBJECT

public:
    Pixmap(const QPixmap &pix, QGraphicsItem *parent = 0)
        : QGraphicsWidget(parent), orig(pix), p(pix)
    {
    }

    void paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *) override
    {
        painter->drawPixmap(QPointF(), p);
    }

    void mousePressEvent(QGraphicsSceneMouseEvent *) override
    {
        emit clicked();
    }

    void setGeometry(const QRectF &rect) override
    {
        QGraphicsWidget::setGeometry(rect);

        if (rect.size().width() > orig.size().width())
            p = orig.scaled(rect.size().toSize());
        else
            p = orig;
    }

Q_SIGNALS:
    void clicked();

private:
    QPixmap orig;
    QPixmap p;
};

class GraphicsView : public QGraphicsView
{
    Q_OBJECT
public:
    GraphicsView(QGraphicsScene *scene, QWidget *parent = 0) : QGraphicsView(scene, parent)
    {
    }

    void resizeEvent(QResizeEvent *) override
    {
        fitInView(sceneRect(), Qt::KeepAspectRatio);
    }
};


void createStates(const QObjectList &objects,
                  const QRect &selectedRect, QState *parent)
{
    for (int i = 0; i < objects.size(); ++i) {
        QState *state = new QState(parent);
        state->assignProperty(objects.at(i), "geometry", selectedRect); //设置状态的属性
        parent->addTransition(objects.at(i), SIGNAL(clicked()), state); //状态业务添加至父状态组中
    }
}

void createAnimations(const QObjectList &objects, QStateMachine *machine)
{
    for (int i=0; i<objects.size(); ++i)
        machine->addDefaultAnimation(new QPropertyAnimation(objects.at(i), "geometry"));    //设置动画
}

int main(int argc, char **argv)
{
    Q_INIT_RESOURCE(appchooser);

    QApplication app(argc, argv);

    Pixmap *p1 = new Pixmap(QPixmap(":/digikam.png"));
    Pixmap *p2 = new Pixmap(QPixmap(":/akregator.png"));
    Pixmap *p3 = new Pixmap(QPixmap(":/accessories-dictionary.png"));
    Pixmap *p4 = new Pixmap(QPixmap(":/k3b.png"));

    p1->setObjectName("p1");
    p2->setObjectName("p2");
    p3->setObjectName("p3");
    p4->setObjectName("p4");

    p1->setGeometry(QRectF(  0.0,   0.0, 64.0, 64.0));
    p2->setGeometry(QRectF(236.0,   0.0, 64.0, 64.0));
    p3->setGeometry(QRectF(236.0, 236.0, 64.0, 64.0));
    p4->setGeometry(QRectF(  0.0, 236.0, 64.0, 64.0));

    QGraphicsScene scene(0, 0, 300, 300);
    scene.setBackgroundBrush(Qt::white);
    scene.addItem(p1);
    scene.addItem(p2);
    scene.addItem(p3);
    scene.addItem(p4);

    GraphicsView window(&scene);
    window.setFrameStyle(0);
    window.setAlignment(Qt::AlignLeft | Qt::AlignTop);
    window.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    window.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);

    QStateMachine machine;
    machine.setGlobalRestorePolicy(QState::RestoreProperties); //设置状态机复原策略,当有新的状态来时,自动复原旧状态的初始值.

    QState *group = new QState(&machine);
    group->setObjectName("group");

    QRect selectedRect(86, 86, 128, 128);

    QState *idleState = new QState(group);
    group->setInitialState(idleState);  //设置空状态为group状态组的初始状态

    QObjectList objects;
    objects << p1 << p2 << p3 << p4;
    createStates(objects, selectedRect, group);
    createAnimations(objects, &machine);

    machine.setInitialState(group); //设置状态机的初始状态,状态机必须设置初始状态才能start().
    machine.start();

    window.resize(300, 300);
    window.show();

    return app.exec();
}

#include "main.moc"

//以下是QT帮助文档中关于QStateMachine的用法的节选. 退出状态机就是Enter顶层的QFinalState.或者显示的调用stop().
//The state machine processes events and takes transitions until a top-level QFinalState is entered;
//the state machine then emits the finished() signal. You can also stop() the state machine explicitly.  
//The stopped() signal is emitted in this case.
//The following snippet shows a state machine that will finish when a button is clicked:
 
   QPushButton button;
 
   QStateMachine machine;
   QState *s1 = new QState();
   s1->assignProperty(&button, "text", "Click me");
 
   QFinalState *s2 = new QFinalState();
   s1->addTransition(&button, SIGNAL(clicked()), s2);
 
   machine.addState(s1);
   machine.addState(s2);
   machine.setInitialState(s1);
   machine.start();