Qt学习（五）QPainter高级

 QPainter高级以及定时器

.h

#ifndef MYWIDGET_H
#define MYWIDGET_H

#include <QWidget>
#include <QGraphicsScene>
#include <QGraphicsLineItem>
#include <QGraphicsPixmapItem>
#include <QGraphicsTextItem>
#include <QGraphicsPixmapItem>
#include <QGraphicsItemAnimation>
#include <QTimeLine>

#include <QPrintPreviewDialog>  // preview
#include <QPrintDialog>         // print

// display scene
#include <QGraphicsView>

#include <QTimer>
#include <QDateTime>

class MyWidget : public QWidget
{
    Q_OBJECT
public:
    explicit MyWidget(QWidget *parent = 0);
    void paintEvent(QPaintEvent *);

    QGraphicsScene* _scene;  // data model
    QGraphicsView* _view;   // show the data model

    void resizeEvent(QResizeEvent *);
    void mousePressEvent(QMouseEvent *);

    QTimer* _timer;
signals:

public slots:
    void slotPaintRequested(QPrinter*);
    void slotTimeout();

};

#endif // MYWIDGET_H

#include "MyWidget.h"
#include <QApplication>
#include <QVBoxLayout>
#include <QMouseEvent>
#include <QDebug>
#include <QPrinter>

MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent)
{
    QGraphicsLineItem* lineItem;
    QGraphicsTextItem* textItem;
    QGraphicsPixmapItem* pixmapItem;

    _view = new QGraphicsView(this);
   // _view->setViewport();
   // _view->setBackgroundBrush(Qt::red);

    _view->setScene(_scene = new QGraphicsScene);

    _scene->addItem(lineItem = new QGraphicsLineItem(QLineF(QPointF(0, 0), QPointF(100, 100))));
    _scene->addItem(textItem = new QGraphicsTextItem("Hello world"));
    _scene->addItem(pixmapItem = new QGraphicsPixmapItem(QPixmap("../aaa.png")));

    QTransform trans;
    trans.rotate(30);
    textItem->setPos(QPointF(200, 300));
    textItem->setTransform(trans);
    textItem->setFont(QFont("aaa", 50, 700, true));

    pixmapItem->setPos(100, 100);

    // Animation == cocos Action
    QGraphicsItemAnimation* animation = new QGraphicsItemAnimation;
    animation->setItem(pixmapItem);

    QTimeLine* timeline = new QTimeLine(3000);
    timeline->setLoopCount(2);

    animation->setTimeLine(timeline);
    animation->setTranslationAt(1, 200, 200);

  //  timeline->start();

#if 0
    _timer = new QTimer();
    _timer->setInterval(1000);
    connect(_timer, SIGNAL(timeout()), this, SLOT(slotTimeout()));
    _timer->start();
#endif
    QTimer::singleShot(1000, this, SLOT(slotTimeout()));//定时器的两种操作方法
}

void MyWidget::slotTimeout()
{
    qDebug() << "Time out";
}

void MyWidget::resizeEvent(QResizeEvent *)
{
    // set the size of _view = MyWidget::size
    _view->setGeometry(QRect(QPoint(0, 0), size()));
}

void MyWidget::paintEvent(QPaintEvent *)
{

}

/* QPixmap, QImage, QBitmap, QPicture */

void MyWidget::mousePressEvent(QMouseEvent *ev)
{
    if(ev->button() == Qt::RightButton)
    {
#if 0
        // save the view
        QPixmap pixmap(size());
        QPainter painter(&pixmap);
        painter.fillRect(QRect(0, 0, size().width(), size().height()), Qt::white);

        _view->render(&painter);
        pixmap.save("../bbb.png");
#endif
#if 0
        print preview
        QPrintPreviewDialog dlg;
        connect(&dlg, SIGNAL(paintRequested(QPrinter*)), this, SLOT(slotPaintRequested(QPrinter*)));
        dlg.exec();
#endif
        QPrintDialog dlg;
        connect(&dlg, SIGNAL(accepted(QPrinter*)), this, SLOT(slotPaintRequested(QPrinter*)));
        dlg.exec();
    }
}

void MyWidget::slotPaintRequested(QPrinter *printer)
{
    QPainter painter(printer);
    _scene->render(&painter);
    painter.drawText(QPoint(100, 100), "Fuck");
}


int main(int argc, char* argv[])
{
    QApplication app (argc,argv);

    MyWidget w;
    w.showMaximized();
    return app.exec();
}

总结：

画家（painter），和纸张（窗口，QPixmap，QPrinter）；画窗口只能在paintEvent中画，图像之间拷贝用render（）；在Qt中图像类有，QPixmap，QImage（平台独立，数据结构用位图结构），QBitmap（灰度图），QPicture（用来记录painter，保存画的轨迹），常用QPixmap（优化过的，和平台相关）；QGraphics对能画的数据结构做了封装，Item，可以独立的Item进行设置，操作；