Qt使用QGraphicsView实现滑动窗体效果

源码已上传至CSDN，http://download.csdn.net/source/2808505

QGraphicsView用来显示一个滚动视图区的QGraphicsScene内容。QGraphicsScene提供了QGraphicsItem的容器功能。通常与QGraphicsView一起使用来描述可视化图形项目。

QGraphicsScene提供了一个视图的场景，通过在这样一个场景之上加入不同的QGraphicsItem来构建视图。而QGraphicsView则提供了一个widget来显示QGraphicsScene的内容。所以要想成功构建一个视图，这三个元素缺一不可。

以下是一个QGraphicsView的例子，实现滑动的窗体效果，工具栏和图片均为场景中的Item。

#include <QtCore>
#include <QtGui>
#include <QtSvg>
/*程序中用到了svg格式的图片，所以需包含QtSvg*/
#define PAGE_COUNT 5
/*定义滑动窗体的窗体数*/

定义工具栏，NviBar继承自QGraphicsRectItem，用法与QGraphicsItem类似。

class NaviBar : public QObject, public QGraphicsRectItem
{
    Q_OBJECT
public:
    NaviBar();
    void setPageOffset(qreal ofs);
signals:
    void pageSelected(int page);
protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0);
private:
    QList<QGraphicsSvgItem*> m_icons;
    QGraphicsRectItem *m_cursor;
};

函数实现

#define ICON_SIZE 50
#define ICON_PAD 4
NaviBar::NaviBar()
        : QGraphicsRectItem()
{
    setRect(0, 0, 5 * ICON_SIZE, ICON_SIZE);
    setPen(Qt::NoPen);
    QStringList names;
    names << "map" << "web" << "home" << "weather" << "contacts";
    for (int i = 0; i < names.count(); ++i) {
        QString fname = names[i];
        fname.prepend(":/icons/");
        fname.append("-page.svg");
        QGraphicsSvgItem *icon = new QGraphicsSvgItem(fname);
        icon->setParentItem(this);
        const int dim = ICON_SIZE - ICON_PAD * 2;
        qreal sw = dim / icon->boundingRect().width();
        qreal sh = dim / icon->boundingRect().height();
        icon->setTransform(QTransform().scale(sw, sh));
        icon->setZValue(2);
        m_icons << icon;
    }
    m_cursor = new QGraphicsRectItem;
    m_cursor->setParentItem(this);
    m_cursor->setRect(0, 0, ICON_SIZE, ICON_SIZE);
    m_cursor->setZValue(1);
    m_cursor->setPen(Qt::NoPen);
    m_cursor->setBrush(QColor(Qt::white));
    m_cursor->setOpacity(0.6);
}
void NaviBar::setPageOffset(qreal ofs)
{
    m_cursor->setPos(ofs * ICON_SIZE, 0);
    for (int i = 0; i < m_icons.count(); ++i) {
        int y = (i == static_cast<int>(ofs + 0.5)) ? ICON_PAD : ICON_PAD * 2;
        m_icons[i]->setPos(i * ICON_SIZE + ICON_PAD, y);
        m_icons[i]->setOpacity(1);
    }
}
void NaviBar::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    emit pageSelected(static_cast<int>(event->pos().x() / ICON_SIZE));
}
void NaviBar::paint(QPainter * painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->setBrush(Qt::white);
    painter->setOpacity(0.2);
    painter->drawRect(option->rect.adjusted(-20, ICON_PAD, 20, 0));
}

定义视图

class ParallaxHome: public QGraphicsView
{
    Q_OBJECT
public:
    QGraphicsScene m_scene;
    NaviBar *m_naviBar;
    QGraphicsPixmapItem *m_wallpaper;
    QTimeLine m_pageAnimator;
    qreal m_pageOffset;
    QList<QGraphicsPixmapItem*> m_items;
    QList<QPointF> m_positions;
public:
    ParallaxHome(QWidget *parent = 0)
            : QGraphicsView(parent)
            , m_pageOffset(-2) {
        setupScene();
        setScene(&m_scene);
        setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
        setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
        setFrameShape(QFrame::NoFrame);
        setWindowTitle("Parallax Home");
        connect(&m_pageAnimator, SIGNAL(frameChanged(int)), SLOT(shiftPage(int)));
        m_pageAnimator.setDuration(500);
        m_pageAnimator.setFrameRange(0, 100);
        m_pageAnimator.setCurveShape(QTimeLine::EaseInCurve);
        pageChanged(static_cast<int>(m_pageOffset));
    }
signals:
    void pageChanged(int page);
public slots:
    void slideRight() {
        if (m_pageAnimator.state() != QTimeLine::NotRunning)
            return;
        int edge = -(m_pageOffset - 1);
        if (edge < PAGE_COUNT)
            slideBy(-1);
    }
    void slideLeft() {
        if (m_pageAnimator.state() != QTimeLine::NotRunning)
            return;
        if (m_pageOffset < 0)
            slideBy(1);
    }
    void slideBy(int dx) {
        int start = m_pageOffset * 1000;
        int end = (m_pageOffset + dx) * 1000;
        m_pageAnimator.setFrameRange(start, end);
        m_pageAnimator.start();
    }
    void choosePage(int page) {
        if (m_pageAnimator.state() != QTimeLine::NotRunning)
            return;
        if (static_cast<int>(-m_pageOffset) == page)
            return;
        slideBy(-page - m_pageOffset);
    }
private slots:
    void shiftPage(int frame) {
        int ww = width();
        int hh = height() - m_naviBar->rect().height();
        int oldPage = static_cast<int>(-m_pageOffset);
        m_pageOffset = static_cast<qreal>(frame) / qreal(1000);
        int newPage = static_cast<int>(-m_pageOffset);
        m_naviBar->setPageOffset(-m_pageOffset);
        if (oldPage != newPage)
            emit pageChanged(newPage);
        int ofs = m_pageOffset * ww;
        for (int i = 0; i < m_items.count(); ++i) {
            QPointF pos = m_positions[i];
            QPointF xy(pos.x() * ww, pos.y() * hh);
            m_items[i]->setPos(xy + QPointF(ofs, 0));
        }
        int center = m_wallpaper->pixmap().width() / 2;
        const int parallax = 3;
        int base = center - (ww / 2) - (PAGE_COUNT >> 1) * (ww / parallax);
        int wofs = base - m_pageOffset * ww / parallax;
        m_wallpaper->setPos(-wofs, 0);
    }
protected:
    void resizeEvent(QResizeEvent *event) {
        Q_UNUSED(event);
        layoutScene();
    }
    void keyPressEvent(QKeyEvent *event) {
        if (event->key() == Qt::Key_Right)
            slideRight();
        if (event->key() == Qt::Key_Left)
            slideLeft();
        event->accept();
    }
private:
    void layoutScene() {
        int ww = width();
        int hh = height();
        m_scene.setSceneRect(0, 0, PAGE_COUNT * ww - 1, hh - 1);
        centerOn(ww / 2, hh / 2);
        int nw = m_naviBar->rect().width();
        int nh = m_naviBar->rect().height();
        m_naviBar->setPos((ww - nw) / 2, hh - nh);
        shiftPage(m_pageOffset * 1000);
    }
    void setupScene() {
        qsrand(QTime::currentTime().second());
        QStringList names;
        names << "brownies" << "cookies" << "mussels" << "pizza" << "sushi";
        names << "chocolate" << "fish" << "pasta" << "puding" << "trouts";
        for (int i = 0; i < PAGE_COUNT * 2; ++i) {
            QString fname = names[i];
            fname.prepend(":/images/");
            fname.append(".jpg");
            QPixmap pixmap(fname);
            pixmap = pixmap.scaledToWidth(200);
            QGraphicsPixmapItem *item = m_scene.addPixmap(pixmap);
            m_items << item;
            qreal x = (i >> 1) + (qrand() % 30) / 100.0;
            qreal y = (i & 1) / 2.0  + (qrand() % 20) / 100.0;
            m_positions << QPointF(x, y);
            item->setZValue(1);
        }
        m_naviBar = new NaviBar;
        m_scene.addItem(m_naviBar);
        m_naviBar->setZValue(2);
        connect(m_naviBar, SIGNAL(pageSelected(int)), SLOT(choosePage(int)));
        m_wallpaper = m_scene.addPixmap(QPixmap(":/icons/surfacing.png"));
        m_wallpaper->setZValue(0);
        m_scene.setItemIndexMethod(QGraphicsScene::NoIndex);
    }
};

main函数

#include "parallaxhome.moc"
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    ParallaxHome w;
    w.resize(360, 640);
    w.show();
    return app.exec();
}

http://blog.csdn.net/huihui1988/article/details/5725955