Qt Graphics View 绘图架构

Qt Graphics View 绘图架构

"QWGraphicsView.h" 头文件代码如下：

#pragma once#include <QGraphicsView>class QWGraphicsView : public QGraphicsView
{Q_OBJECTpublic:QWGraphicsView(QWidget *parent);~QWGraphicsView();protected:void mouseMoveEvent(QMouseEvent *event);void mousePressEvent(QMouseEvent *event);signals:void mouseMovePoint(QPoint point);void mouseClicked(QPoint point);
};

mouseMoveEvent()是鼠标移动事件，代码如下：

//鼠标移动事件
void QWGraphicsView::mouseMoveEvent(QMouseEvent *event)
{QPoint point = event->pos();//QGraphicsView的坐标emit mouseMovePoint(point); //释放信号QGraphicsView::mouseMoveEvent(event);
}

       在此事件响应代码里，通过事件的pos()函数获取鼠标光标在视图中的坐标point，然后作为参数发射 mouseMovePoint(point)信号。这样，若在其他地方编写槽函数与此信号关联，就可以对鼠标移动事件作出响应。

mousePressEvent()是鼠标按键按下事件，代码如下：

//鼠标左键按下事件
void QWGraphicsView::mousePressEvent(QMouseEvent *event)
{if (event->button() == Qt::LeftButton){QPoint point = event->pos();//QGraphicsView的坐标emit mouseClicked(point);//释放信号}QGraphicsView::mousePressEvent(event);
}

       在此事件响应代码里，首先判断是否是鼠标左键按下，然后通过事件的pos()函数获取鼠标光标在视图中的坐标point，然后作为参数发射mouseClicked(point)信号。

"sample8_4QGraphicsView.h"  头文件代码如下：

#pragma once#include <QtWidgets/QMainWindow>
#include "ui_sample8_4QGraphicsView.h"#include    <QGraphicsScene>
#include    <QLabel>class sample8_4QGraphicsView : public QMainWindow
{Q_OBJECTpublic:sample8_4QGraphicsView(QWidget *parent = Q_NULLPTR);private:Ui::sample8_4QGraphicsViewClass ui;protected:void resizeEvent(QResizeEvent *event);private:QGraphicsScene  *scene;QLabel  *labViewCord;QLabel  *labSceneCord;QLabel  *labItemCord;void iniGraphicsSystem(); //创建Graphics View的各项private slots:void on_mouseMovePoint(QPoint point);void on_mouseClicked(QPoint point);};

#include "sample8_4QGraphicsView.h"#include  "ui_sample8_4QGraphicsView.h"
#include   <QGraphicsEllipseItem>//解决QT中中文显示乱码问题
#pragma execution_character_set("utf-8")sample8_4QGraphicsView::sample8_4QGraphicsView(QWidget *parent): QMainWindow(parent)
{ui.setupUi(this);labViewCord = new QLabel("View 坐标：");labViewCord->setMinimumWidth(150);ui.statusBar->addWidget(labViewCord);labSceneCord = new QLabel("Scene 坐标：");labSceneCord->setMinimumWidth(150);ui.statusBar->addWidget(labSceneCord);labItemCord = new QLabel("Item 坐标：");labItemCord->setMinimumWidth(150);ui.statusBar->addWidget(labItemCord);ui.View->setCursor(Qt::CrossCursor);ui.View->setMouseTracking(true);ui.View->setDragMode(QGraphicsView::RubberBandDrag);QObject::connect(ui.View, SIGNAL(mouseMovePoint(QPoint)),this, SLOT(on_mouseMovePoint(QPoint)));QObject::connect(ui.View, SIGNAL(mouseClicked(QPoint)),this, SLOT(on_mouseClicked(QPoint)));iniGraphicsSystem();
}

鼠标移动事件响应：

//鼠标移动事件，point是 GraphicsView的坐标,物理坐标
void sample8_4QGraphicsView::on_mouseMovePoint(QPoint point)
{labViewCord->setText(QString::asprintf("View 坐标：%d,%d", point.x(), point.y()));QPointF pointScene = ui.View->mapToScene(point); //转换到Scene坐标labSceneCord->setText(QString::asprintf("Scene 坐标：%.0f,%.0f", pointScene.x(), pointScene.y()));
}

鼠标单击事件响应：

//鼠标单击事件
void sample8_4QGraphicsView::on_mouseClicked(QPoint point)
{QPointF pointScene = ui.View->mapToScene(point); //转换到Scene坐标QGraphicsItem  *item = NULL;item = scene->itemAt(pointScene, ui.View->transform()); //获取光标下的绘图项if (item != NULL) //有绘图项{QPointF pointItem = item->mapFromScene(pointScene); //转换为绘图项的局部坐标labItemCord->setText(QString::asprintf("Item 坐标：%.0f,%.0f", pointItem.x(), pointItem.y()));}
}

窗口变化大小时的事件：

//窗口变化大小时的事件
void sample8_4QGraphicsView::resizeEvent(QResizeEvent *event)
{ Q_UNUSED(event);//Graphics View坐标，左上角总是（0,0），宽度=，长度=ui.labViewSize->setText(QString::asprintf("Graphics View坐标，左上角总是（0,0），宽度=%d，高度=%d",ui.View->width(), ui.View->height()));QRectF  rectF = ui.View->sceneRect(); //Scene的矩形区ui.LabSceneRect->setText(QString::asprintf("QGraphicsView::sceneRect=(Left,Top,Width,Height)=%.0f,%.0f,%.0f,%.0f",rectF.left(), rectF.top(), rectF.width(), rectF.height()));
}

构造Graphics View的各项：

//构造Graphics View的各项
void sample8_4QGraphicsView::iniGraphicsSystem()
{QRectF   rect(-200, -100, 400, 200);//左上角坐标，宽度，高度scene = new QGraphicsScene(rect); //scene逻辑坐标系定义ui.View->setScene(scene);//画一个矩形框，大小等于sceneQGraphicsRectItem *item = new QGraphicsRectItem(rect); //矩形框正好等于scene的大小item->setFlags(QGraphicsItem::ItemIsSelectable     //可选，可以有焦点，但是不能移动| QGraphicsItem::ItemIsFocusable);QPen    pen;pen.setWidth(2);item->setPen(pen);//item->setPos(500,0);//缺省位置在scene的（0,0）scene->addItem(item);//一个位于scene中心的椭圆，测试局部坐标QGraphicsEllipseItem *item2 = new QGraphicsEllipseItem(-100, -50, 200, 100); //矩形框内创建椭圆,绘图项的局部坐标，左上角(-100,-50)，宽200，高100item2->setPos(0, 0);//设置椭圆中心位置item2->setBrush(QBrush(Qt::blue));item2->setFlags(QGraphicsItem::ItemIsMovable //可移动| QGraphicsItem::ItemIsSelectable  //可选择| QGraphicsItem::ItemIsFocusable); //可获得焦点scene->addItem(item2);//一个圆，中心位于scene的边缘QGraphicsEllipseItem *item3 = new QGraphicsEllipseItem(-50, -50, 100, 100); //矩形框内创建椭圆,绘图项的局部坐标，左上角(-100,-50)，宽200，高100item3->setPos(rect.right(), rect.bottom());//设置圆中心位置item3->setBrush(QBrush(Qt::red));item3->setFlags(QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemIsSelectable | QGraphicsItem::ItemIsFocusable);scene->addItem(item3);scene->clearSelection();//item->setSelected(true);//ui.View->setDragMode(QGraphicsView::RubberBandDrag);
}

运行结果如下：

"QWGraphicsView.cpp" 文件代码如下：

#include "QWGraphicsView.h"#include    <QMouseEvent>
#include    <QPoint>QWGraphicsView::QWGraphicsView(QWidget *parent): QGraphicsView(parent)
{
}QWGraphicsView::~QWGraphicsView()
{
}//鼠标移动事件
void QWGraphicsView::mouseMoveEvent(QMouseEvent *event)
{QPoint point = event->pos();//QGraphicsView的坐标emit mouseMovePoint(point); //释放信号QGraphicsView::mouseMoveEvent(event);
}//鼠标左键按下事件
void QWGraphicsView::mousePressEvent(QMouseEvent *event)
{if (event->button() == Qt::LeftButton){QPoint point = event->pos();//QGraphicsView的坐标emit mouseClicked(point);//释放信号}QGraphicsView::mousePressEvent(event);
}

"sample8_4QGraphicsView.cpp"  文件代码如下：

#include "sample8_4QGraphicsView.h"#include  "ui_sample8_4QGraphicsView.h"
#include   <QGraphicsEllipseItem>//解决QT中中文显示乱码问题
#pragma execution_character_set("utf-8")sample8_4QGraphicsView::sample8_4QGraphicsView(QWidget *parent): QMainWindow(parent)
{ui.setupUi(this);labViewCord = new QLabel("View 坐标：");labViewCord->setMinimumWidth(150);ui.statusBar->addWidget(labViewCord);labSceneCord = new QLabel("Scene 坐标：");labSceneCord->setMinimumWidth(150);ui.statusBar->addWidget(labSceneCord);labItemCord = new QLabel("Item 坐标：");labItemCord->setMinimumWidth(150);ui.statusBar->addWidget(labItemCord);ui.View->setCursor(Qt::CrossCursor);ui.View->setMouseTracking(true);ui.View->setDragMode(QGraphicsView::RubberBandDrag);QObject::connect(ui.View, SIGNAL(mouseMovePoint(QPoint)),this, SLOT(on_mouseMovePoint(QPoint)));QObject::connect(ui.View, SIGNAL(mouseClicked(QPoint)),this, SLOT(on_mouseClicked(QPoint)));iniGraphicsSystem();
}//鼠标移动事件，point是 GraphicsView的坐标,物理坐标
void sample8_4QGraphicsView::on_mouseMovePoint(QPoint point)
{labViewCord->setText(QString::asprintf("View 坐标：%d,%d", point.x(), point.y()));QPointF pointScene = ui.View->mapToScene(point); //转换到Scene坐标labSceneCord->setText(QString::asprintf("Scene 坐标：%.0f,%.0f", pointScene.x(), pointScene.y()));
}//鼠标单击事件
void sample8_4QGraphicsView::on_mouseClicked(QPoint point)
{QPointF pointScene = ui.View->mapToScene(point); //转换到Scene坐标QGraphicsItem  *item = NULL;item = scene->itemAt(pointScene, ui.View->transform()); //获取光标下的绘图项if (item != NULL) //有绘图项{QPointF pointItem = item->mapFromScene(pointScene); //转换为绘图项的局部坐标labItemCord->setText(QString::asprintf("Item 坐标：%.0f,%.0f", pointItem.x(), pointItem.y()));}
}//构造Graphics View的各项
void sample8_4QGraphicsView::iniGraphicsSystem()
{QRectF   rect(-200, -100, 400, 200);//左上角坐标，宽度，高度scene = new QGraphicsScene(rect); //scene逻辑坐标系定义ui.View->setScene(scene);//画一个矩形框，大小等于sceneQGraphicsRectItem *item = new QGraphicsRectItem(rect); //矩形框正好等于scene的大小item->setFlags(QGraphicsItem::ItemIsSelectable     //可选，可以有焦点，但是不能移动| QGraphicsItem::ItemIsFocusable);QPen    pen;pen.setWidth(2);item->setPen(pen);//item->setPos(500,0);//缺省位置在scene的（0,0）scene->addItem(item);//一个位于scene中心的椭圆，测试局部坐标QGraphicsEllipseItem *item2 = new QGraphicsEllipseItem(-100, -50, 200, 100); //矩形框内创建椭圆,绘图项的局部坐标，左上角(-100,-50)，宽200，高100item2->setPos(0, 0);//设置椭圆中心位置item2->setBrush(QBrush(Qt::blue));item2->setFlags(QGraphicsItem::ItemIsMovable //可移动| QGraphicsItem::ItemIsSelectable  //可选择| QGraphicsItem::ItemIsFocusable); //可获得焦点scene->addItem(item2);//一个圆，中心位于scene的边缘QGraphicsEllipseItem *item3 = new QGraphicsEllipseItem(-50, -50, 100, 100); //矩形框内创建椭圆,绘图项的局部坐标，左上角(-100,-50)，宽200，高100item3->setPos(rect.right(), rect.bottom());//设置圆中心位置item3->setBrush(QBrush(Qt::red));item3->setFlags(QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemIsSelectable | QGraphicsItem::ItemIsFocusable);scene->addItem(item3);scene->clearSelection();//item->setSelected(true);//ui.View->setDragMode(QGraphicsView::RubberBandDrag);
}//窗口变化大小时的事件
void sample8_4QGraphicsView::resizeEvent(QResizeEvent *event)
{ Q_UNUSED(event);//Graphics View坐标，左上角总是（0,0），宽度=，长度=ui.labViewSize->setText(QString::asprintf("Graphics View坐标，左上角总是（0,0），宽度=%d，高度=%d",ui.View->width(), ui.View->height()));QRectF  rectF = ui.View->sceneRect(); //Scene的矩形区ui.LabSceneRect->setText(QString::asprintf("QGraphicsView::sceneRect=(Left,Top,Width,Height)=%.0f,%.0f,%.0f,%.0f",rectF.left(), rectF.top(), rectF.width(), rectF.height()));
}

"main.cpp"  文件代码如下：

#include "sample8_4QGraphicsView.h"
#include <QtWidgets/QApplication>int main(int argc, char *argv[])
{QApplication a(argc, argv);sample8_4QGraphicsView w;w.show();return a.exec();
}

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