Qt学习之路(32): 一个简易画板的实现(Graphics View)

#include  "mainwindow.h" 
 
MainWindow::MainWindow(QWidget *parent) 
        : QMainWindow(parent) 
{ 
        QToolBar *bar =  this->addToolBar( "Tools"); 
        QActionGroup *group =  new QActionGroup(bar); 
 
        QAction *drawLineAction =  new QAction( "Line", bar); 
        drawLineAction->setIcon(QIcon( ":/line.png")); 
        drawLineAction->setToolTip(tr( "Draw a line.")); 
        drawLineAction->setStatusTip(tr( "Draw a line.")); 
        drawLineAction->setCheckable( true); 
        drawLineAction->setChecked( true); 
        group->addAction(drawLineAction); 
 
        bar->addAction(drawLineAction); 
        QAction *drawRectAction =  new QAction( "Rectangle", bar); 
        drawRectAction->setIcon(QIcon( ":/rect.png")); 
        drawRectAction->setToolTip(tr( "Draw a rectangle.")); 
        drawRectAction->setStatusTip(tr( "Draw a rectangle.")); 
        drawRectAction->setCheckable( true); 
        group->addAction(drawRectAction); 
        bar->addAction(drawRectAction); 
 
        QLabel *statusMsg =  new QLabel; 
        statusBar()->addWidget(statusMsg); 
 
        PaintWidget *paintWidget =  new PaintWidget( this); 
        QGraphicsView *view =  new QGraphicsView(paintWidget,  this); 
        setCentralWidget(view); 
 
        connect(drawLineAction, SIGNAL(triggered()), 
                         this, SLOT(drawLineActionTriggered())); 
        connect(drawRectAction, SIGNAL(triggered()), 
                         this, SLOT(drawRectActionTriggered())); 
        connect( this, SIGNAL(changeCurrentShape(Shape::Code)), 
                        paintWidget, SLOT(setCurrentShape(Shape::Code))); 
} 
 
void MainWindow::drawLineActionTriggered() 
{ 
        emit changeCurrentShape(Shape::Line); 
} 
 
void MainWindow::drawRectActionTriggered() 
{ 
        emit changeCurrentShape(Shape::Rect); 
} 

#ifndef PAINTWIDGET_H 
#define PAINTWIDGET_H 
 
#include <QtGui> 
#include <QDebug> 
 
#include  "shape.h" 
#include  "line.h" 
#include  "rect.h" 
 
class PaintWidget :  public QGraphicsScene 
{ 
        Q_OBJECT 
 
public: 
        PaintWidget(QWidget *parent = 0); 
 
public slots: 
         void setCurrentShape(Shape::Code s) 
        { 
                 if(s != currShapeCode) { 
                        currShapeCode = s; 
                } 
        } 
 
protected: 
         void mousePressEvent(QGraphicsSceneMouseEvent * event);
         void mouseMoveEvent(QGraphicsSceneMouseEvent * event);
         void mouseReleaseEvent(QGraphicsSceneMouseEvent * event);
 
private: 
        Shape::Code currShapeCode; 
        Shape *currItem; 
         bool perm; 
}; 
 
#endif  // PAINTWIDGET_H

#include  "paintwidget.h" 
 
PaintWidget::PaintWidget(QWidget *parent) 
        : QGraphicsScene(parent), currShapeCode(Shape::Line), currItem(NULL), perm( false) 
{ 
 
} 
 
void PaintWidget::mousePressEvent(QGraphicsSceneMouseEvent * event) 
{ 
         switch(currShapeCode) 
        { 
         case Shape::Line: 
                { 
                        Line *line =  new Line; 
                        currItem = line; 
                        addItem(line); 
                         break; 
                } 
         case Shape::Rect: 
                { 
                        Rect *rect =  new Rect; 
                        currItem = rect; 
                        addItem(rect); 
                         break; 
                } 
        } 
         if(currItem) { 
                currItem->startDraw( event); 
                perm =  false; 
        } 
        QGraphicsScene::mousePressEvent( event); 
} 
 
void PaintWidget::mouseMoveEvent(QGraphicsSceneMouseEvent * event) 
{ 
         if(currItem && !perm) { 
                currItem->drawing( event); 
        } 
        QGraphicsScene::mouseMoveEvent( event); 
} 
 
void PaintWidget::mouseReleaseEvent(QGraphicsSceneMouseEvent * event) 
{ 
        perm =  true; 
        QGraphicsScene::mouseReleaseEvent( event); 
}

#ifndef SHAPE_H 
#define SHAPE_H 
 
#include <QtGui> 
 
class Shape 
{ 
public: 
 
         enum Code { 
                Line, 
                Rect 
        }; 
 
        Shape(); 
 
         virtual  void startDraw(QGraphicsSceneMouseEvent *  event) = 0; 
         virtual  void drawing(QGraphicsSceneMouseEvent *  event) = 0; 
}; 
 
#endif  // SHAPE_H

#include  "shape.h" 
 
Shape::Shape() 
{ 
} 

#ifndef LINE_H 
#define LINE_H 
 
#include <QGraphicsLineItem> 
#include  "shape.h" 
 
class Line :  public Shape,  public QGraphicsLineItem 
{ 
public: 
        Line(); 
 
         void startDraw(QGraphicsSceneMouseEvent *  event); 
         void drawing(QGraphicsSceneMouseEvent *  event); 
}; 
 
#endif  // LINE_H

#include  "line.h" 
 
Line::Line() 
{ 
} 
 
void Line::startDraw(QGraphicsSceneMouseEvent *  event) 
{ 
        setLine(QLineF( event->scenePos(),  event->scenePos())); 
} 
 
void Line::drawing(QGraphicsSceneMouseEvent *  event) 
{ 
        QLineF newLine(line().p1(),  event->scenePos()); 
        setLine(newLine); 
} 

#ifndef RECT_H 
#define RECT_H 
 
#include <QGraphicsRectItem> 
#include  "shape.h" 
 
class Rect :  public Shape,  public QGraphicsRectItem 
{ 
public: 
        Rect(); 
 
         void startDraw(QGraphicsSceneMouseEvent *  event); 
         void drawing(QGraphicsSceneMouseEvent *  event); 
}; 
 
#endif  // RECT_H

#include  "rect.h" 
 
Rect::Rect() 
{ 
} 
 
void Rect::startDraw(QGraphicsSceneMouseEvent *  event) 
{ 
        setRect(QRectF( event->scenePos(), QSizeF(0, 0))); 
} 
 
void Rect::drawing(QGraphicsSceneMouseEvent *  event) 
{ 
        QRectF r(rect().topLeft(), 
                         QSizeF( event->scenePos().x() - rect().topLeft().x(),  event->scenePos().y() - rect().topLeft().y())); 
        setRect(r); 
} 

setFlag(QGraphicsItem::ItemIsMovable,  true); 
setFlag(QGraphicsItem::ItemIsSelectable,  true);