qt学习笔记（五） QGraphicsPixmapItem与QGraphicsScene的编程实例 图标拖动渐变效果

应大家的要求，还是把完整的工程文件贴出来，大家省点事：http://www.kuaipan.cn/file/id_48923272389086450.htm

先看看运行效果，我用的群创7寸屏，主机是mini2440，分辨率是800*480，程序写比较粗糙，但对初学者还是有一点启发，大家一起进步。

qt中提供了QGphicsView，QGraphicsScene，QGraphicsItem，QGraphicsPixmapItem是QGraphicsItem的子类

分辨创建它们的实例：view，scene，item，然后通过各自的方法scene->addItem(item);view->setScene(scene);就可以达到类似下图的效果，想要进一步定制，则要继承QGraphicsItem或QGraphicsPixmapItem，然后重写paint()、boundingRect()等方法，此外如果还想要获取鼠标事件，重写mousePressEvent等事件就好了，注意，一旦重写了mousePressEvent方法，就以为了qt不会再自动处理item的任何press事件了，可以在你重写的mousePressEvent方法中最后添加QGraphicsItem::mousePressEvent(event);解决这个问题，就是说你获取到了鼠标事件，但是依然让qt处理这个鼠标事件。

程序中的item可以水平拖动，拖动的同时图标大小会渐变，中间最大，两边渐小。

图1



图2



图3



下面是源程序目录结构：



mainwindow.h与main.cpp是qt自动产生的代码，我没有产生窗口ui

myscene.h与某与scene.cpp是定义了类MyScene，继承自QGraphicsScene，我的目的是要获取其鼠标事件

nodeui.h与nodeui.cpp是定义了类NodeUI，继承自QGraphicsPixmapItem，目的相当多。

下面具体的源文件：myscene.h与myscene.cpp相对简单，就实现了一个功能

myscene.h

#ifndef MYSCENE_H
#define MYSCENE_H

#include <QGraphicsScene>

class MyScene : public QGraphicsScene
{
Q_OBJECT
public:
explicit MyScene(QObject *parent = 0);

private:
void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
void mousePressEvent(QGraphicsSceneMouseEvent *event);
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);

signals:
void isMoving(QPointF &pos);

public slots:

private:
QPointF  beforePos;
QPointF  releasePos;
};

#endif // MYSCENE_H

myscene.cpp

#include "myscene.h"
#include <QGraphicsSceneMouseEvent>
#include <QPointF>
#include <QDebug>

MyScene::MyScene(QObject *parent) :
QGraphicsScene(parent)
{
}
void MyScene::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
//QPointF pos = event->scenePos();
QPointF pos(event->scenePos().x()-beforePos.x(),event->scenePos().y()-beforePos.y());
emit isMoving(pos);
//qDebug()<<"x:"<<pos.x()<<"y:"<<pos.y();
}
void MyScene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
beforePos = event->scenePos();
}
void MyScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
releasePos = event->scenePos();
}

再看nodeui.h与nodeui.cpp，在原来的QGraphicsPixmapItem基础上又假如了点自己的东西

#ifndef NODEUI_H
#define NODEUI_H

#include <QGraphicsPixmapItem>
#include <QGraphicsItem>
#include <QStyleOptionGraphicsItem>
#include <QPainter>
#include <QGraphicsSceneMouseEvent>
#include <QPointF>

class NodeUI : public QObject,public QGraphicsPixmapItem
{
Q_OBJECT
public:
NodeUI();
NodeUI(QString &file,QString &text,int imagesize=80);

//setup function
void setMyPixmap(QString &file,int size);
void setMyText(QString &text);
QString getMyText();
//virtual function
QRectF boundingRect() const;
QPainterPath shape() const;
signals:
void nodeIsMoving(QPointF &pos);
void nodeIsPressed();

protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
private:
//QString myImage;
QString myText;

};

#endif // NODEUI_H

nideui.cpp

#include "nodeui.h"
#include <QPixmap>
#include <iostream>
#include <QDebug>

NodeUI::NodeUI()
{
}
/*note: imagesize = 80 is in the nodeui.h*/
NodeUI::NodeUI(QString &file,QString &text,int imagesize)
{

setMyText(text);
setMyPixmap(file,imagesize);
}

void NodeUI::setMyText(QString &text)
{
myText = text;
}

void NodeUI::setMyPixmap(QString &file,int size)
{
//myImage = file;
QPixmap pixmap;
pixmap.load(file);
pixmap= pixmap.scaled(size,size,Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
setPixmap(pixmap);
}
QRectF NodeUI::boundingRect() const
{
QRect rect = this->pixmap().rect();
//return QRectF(rect);
return QRectF(0,0,rect.width(),rect.width()+15);
}

void NodeUI::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
QWidget *widget)
{
QPixmap pixmap = this->pixmap();
QRect rect = pixmap.rect();

painter->drawPixmap(rect,pixmap);

//print name,calculate the text's heigh & width for center layout
QPen pen(Qt::black);
painter->setPen(pen);
painter->setRenderHint(QPainter::Antialiasing);
QFont font("Verdana",8, QFont::Normal);
painter->setFont(font);
painter->drawText(QRectF(0,rect.height(),rect.width(),15),Qt::AlignCenter,myText);

if (option->state & QStyle::State_Sunken)
{
QRectF rect1 = boundingRect();
//QPen pen(Qt::darkGreen);
painter->setPen(QPen(Qt::darkGreen));
}else
{

}
}
QPainterPath NodeUI::shape() const
{
QRectF rect = boundingRect();

QPainterPath path;
path.addRoundRect(rect, 5,5);
return path;
}

void NodeUI::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
emit nodeIsPressed();
qDebug()<<"pressed";
QGraphicsItem::mousePressEvent(event);
}
void NodeUI::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
update(boundingRect());
QGraphicsItem::mouseReleaseEvent(event);
}
QString NodeUI::getMyText()
{
return myText;
}

最后是scene与item的文件mainwindow.cpp，继承了QMainWindow，作用就是画一个应用程序框架

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QtGui/QMainWindow>
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QPointF>
#include "nodeui.h"
#include "myscene.h"
#include <QMap>

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
MainWindow(QWidget *parent = 0);
~MainWindow();

NodeUI *selectedNodeUI();
bool isNodeUiClicked();
void nodeUiSizeAdjust();
//var

protected:

private:

void GetScreenInfo();
QGraphicsView *view;
//QGraphicsScene *scene;
MyScene *scene;
//instead of (NodeUI *nodeui;)&(QPointF nodeUiPos;)
//目前弃用，由于QMap的顺序无法人为设定，按照内部key自动升序
//QMap<NodeUI*,QPointF>nodeUiMaps;
//NodeUI *currentNodeUI;
//nodeui pressed or released
volatile bool mPressed;

QList<NodeUI*> nodeUiLists;
QList<QPointF> nodeUiPosLists;
QList<QPixmap> nodeUiPixmapLists;
/*
struct {
QList<NodeUI*> nodelists;
QList<QPointF> poslists;
}ss;
*/
//弃用
NodeUI *nodeui;
QPointF nodeUiPos;

//sceen size info;
qint16 sceenSizeX;
qint16 sceenSizeY;
private slots:
void isMoving(QPointF &pos);
void isPressed();
void isReleased();
void selectionChanged();

signals:
void nodeUiClicked(NodeUI* node);
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include <QDesktopWidget>
#include <QApplication>
#include <QPixmap>
#include <QGraphicsItem>
#include <QMouseEvent>
#include <QWidget>
#include <QGraphicsPixmapItem>
#include <QMessageBox>
#include <QDebug>

const qreal MY_NODEUI_POS_Y = 200;
const qreal MY_NODEUI_DIS = 110;
const qreal MY_NODEUI_STA = 90;
const int   MYNODEUI_SIZE = 100;
const int   MYNODEUI_SIZE_M = 20;
const int   SCREEN_SIZE = 800;
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
//初始化
mPressed = false;
//get windows size
GetScreenInfo();

view = new QGraphicsView;
scene = new MyScene();
scene->setSceneRect(0,0,800,480);

//new
QString file;
QString text;
QPointF pos;
NodeUI* node;

//HOME:1
file = QString(":/images/home.png");
text = QString("Home");
pos = QPointF(MY_NODEUI_STA,MY_NODEUI_POS_Y);

node = new NodeUI(file,text,MYNODEUI_SIZE);
node->setPos(pos);
nodeUiLists.append(node);
nodeUiPosLists.append(pos);
nodeUiPixmapLists.append(node->pixmap());
/*
here cannot delete node!!!!!!!!!!!!!!!
delete node;
*/

//VIDIO:2
file = QString(":/images/securitycamera.png");
text = QString("Vidio");
pos = QPointF(MY_NODEUI_STA+MY_NODEUI_DIS*1,MY_NODEUI_POS_Y);

node = new NodeUI(file,text,MYNODEUI_SIZE);
node->setPos(pos);
nodeUiLists.append(node);
nodeUiPosLists.append(pos);
nodeUiPixmapLists.append(node->pixmap());

//APPLICATION:3
file = QString(":/images/application.png");
text = QString("Application");
pos = QPointF(MY_NODEUI_STA+MY_NODEUI_DIS*2,MY_NODEUI_POS_Y);

node = new NodeUI(file,text,MYNODEUI_SIZE);
node->setPos(pos);
nodeUiLists.append(node);
nodeUiPosLists.append(pos);
nodeUiPixmapLists.append(node->pixmap());

//NETWORK:4
file = QString(":/images/network-2.png");
text = QString("Network");
pos = QPointF(MY_NODEUI_STA+MY_NODEUI_DIS*3,MY_NODEUI_POS_Y);

node = new NodeUI(file,text,MYNODEUI_SIZE);
node->setPos(pos);
nodeUiLists.append(node);
nodeUiPosLists.append(pos);
nodeUiPixmapLists.append(node->pixmap());

//COMPUTER:5
file = QString(":/images/smartphone.png");
text = QString("Phone");
pos = QPointF(MY_NODEUI_STA+MY_NODEUI_DIS*4,MY_NODEUI_POS_Y);

node = new NodeUI(file,text,MYNODEUI_SIZE);
node->setPos(pos);
nodeUiLists.append(node);
nodeUiPosLists.append(pos);
nodeUiPixmapLists.append(node->pixmap());

//CUSTOMIZE:5
file = QString(":/images/customize.png");
text = QString("Setting");
pos = QPointF(MY_NODEUI_STA+MY_NODEUI_DIS*5,MY_NODEUI_POS_Y);

node = new NodeUI(file,text,MYNODEUI_SIZE);
node->setPos(pos);
nodeUiLists.append(node);
nodeUiPosLists.append(pos);
nodeUiPixmapLists.append(node->pixmap());

//重新计算UiSize
nodeUiSizeAdjust();

int i = 0;
foreach(NodeUI* node_temp,nodeUiLists)
{

node_temp->setFlags(QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemIsSelectable);

qDebug()<<"name:"<<node_temp->getMyText()<<nodeUiPosLists.at(i);

scene->addItem(node_temp);

i++;
}

//用于按钮的单机

view->setScene(scene);
//set drag mode
//view->setDragMode(QGraphicsView::RubberBandDrag);
view->setRenderHints(QPainter::Antialiasing);
//no menu
view->setContextMenuPolicy(Qt::NoContextMenu);

view->setBackgroundBrush(QImage(":/images/shuibo2.jpg"));
//view->setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);
//view->setCacheMode(QGraphicsView::CacheBackground);
setCentralWidget(view);
setWindowTitle(tr("Main Window"));
}
//槽，当scene鼠标拖拽是执行
//控制UI图标的水平
void MainWindow::isMoving(QPointF &pos)
{
int i=0;
if(mPressed){
foreach(NodeUI* node,nodeUiLists)
{
node->setPos(nodeUiPosLists.at(i).x()+pos.x(),MY_NODEUI_POS_Y);
i++;
}
nodeUiSizeAdjust();
}
}
//槽，当nodeui鼠标按下时执行,调用selectedNodeUI函数，更新currentNodeUI变量
//除此之外，selectionChanged()也是一个槽，由scene调用
void MainWindow::isPressed()
{
selectionChanged();
mPressed = true;
}
//槽，当nodeui鼠标释放时执行
//应当设置标志位，让UI图片停止对鼠标拖动事件的响应
void MainWindow::isReleased()
{
mPressed = false;
if(isNodeUiClicked())
qDebug()<<"clicked";
qDebug()<<"release";
}

//槽，当scene的selectedItem变化时，发送同名信号到此槽
void MainWindow::selectionChanged()
{
int i=0,j=0;
QList<QGraphicsItem *> items = scene->selectedItems();
if (items.count() == 1) {
//当前所选择的UI图标的坐标
QPointF pos = items.first()->pos();
NodeUI* node_temp = dynamic_cast<NodeUI *>(items.first());
qDebug()<<"items.x:"<<pos.x()<<"items.y:"<<pos.y();

foreach(NodeUI* node,nodeUiLists)
{
if(node == node_temp)
break;
i++;
}
j=i;
i=0;
foreach(QPointF ppos,nodeUiPosLists)
{
nodeUiPosLists[i].setX((i-j)*MY_NODEUI_DIS+pos.x());
nodeUiPosLists[i].setY(MY_NODEUI_POS_Y);
i++;
}

} else {
return;
}
}
//判断是否Nodeui接收的是否是单击信号。
//判断依据是当前单击的nodeui对象的pos与存储在nodeUiPosListsd的位置比较，相等则为单击
bool MainWindow::isNodeUiClicked()
{
int i=-1;
QList<QGraphicsItem *> items = scene->selectedItems();
if (items.count() == 1) {
QPointF pos = items.first()->pos();
NodeUI* node_temp = dynamic_cast<NodeUI *>(items.first());
if(pos ==nodeUiPosLists.at(i)){
//emit nodeUiClicked(node_temp);
QMessageBox::information(this,"New Window","will open : "+node_temp->getMyText());
return true;
}
}
return false;
}
void MainWindow::nodeUiSizeAdjust()
{
quint16 i=0;
foreach(NodeUI* node,nodeUiLists)
{
//qDebug()<<"i= "<<i;
QPointF pos=node->pos();

pos.setX(node->pos().x()+MYNODEUI_SIZE/2);
//pos.setX(node->pos().x()+node->pixmap().width());
if(pos.x()>=0 && pos.x()<=SCREEN_SIZE/2)
{
//(MYNODEUI_SIZE-MYNODEUI_SIZE_M)/(SCREEN_SIZE/2)==(size-20)/pos.x()
quint16 size=pos.x()/5+20;
QPixmap pixmap = nodeUiPixmapLists.at(i);
//QPixmap pixmap = nodeUiLists.at(i)->pixmap();
pixmap = pixmap.scaled(size,size,Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
nodeUiLists[i]->setPixmap(pixmap);
}

//if(pos.x()>SCREEN_SIZE/2 && pos.x()<=SCREEN_SIZE)
if(pos.x()>SCREEN_SIZE/2 && pos.x()<=SCREEN_SIZE+10)
{
//(MYNODEUI_SIZE-MYNODEUI_SIZE_M)/(SCREEN_SIZE/2)==(size-20)/pos.x()
quint16 size=(SCREEN_SIZE-pos.x())/5+20;
QPixmap pixmap = nodeUiPixmapLists.at(i);
//QPixmap pixmap = nodeUiLists.at(i)->pixmap();
pixmap = pixmap.scaled(size,size,Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
nodeUiLists[i]->setPixmap(pixmap);
}
i++;
}
}
MainWindow::~MainWindow()
{
}
//获取设备分辨率的呢个信息
void MainWindow::GetScreenInfo()
{
QDesktopWidget* desktopWidget = QApplication::desktop();
//获取可用桌面大小
//QRect deskRect = desktopWidget->availableGeometry();
//获取设备屏幕大小
QRect screenRect = desktopWidget->screenGeometry();

sceenSizeX = screenRect.width();
sceenSizeY = screenRect.height();

//获取系统设置的屏幕个数（屏幕拷贝方式该值为1）
//g_nScreenCount = desktopWidget->screenCount();
}

最后是main.cpp

实例化MainWindow

#include <QtGui/QApplication>
#include "mainwindow.h"

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;

w.setWindowOpacity(1);
w.setWindowFlags(Qt::FramelessWindowHint);
w.setAttribute(Qt::WA_TranslucentBackground);
w.show();
//w.showFullScreen();

return a.exec();
}

大概都写了注解了，其实看看一个名称也该大概了解其作用，写这程序时遇到的问题都记录在了前一篇qt学习笔记（四）中，记录一下，以备不时之需