QGraphicsView程式基本結構和功能實現

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H


#include <QMainWindow>
#include <QLabel>
#include<QGraphicsScene>
#include<QGraphicsItem>
#include"qwgraphicsview.h"


namespace Ui {
class MainWindow;
}


class MainWindow : public QMainWindow
{
Q_OBJECT
private:
    QGraphicsScene  *scene;
    QLabel  *labViewCord;
    QLabel  *labSceneCord;
    QLabel  *labItemCord;
    void iniGraphicsSystem(); //建立Graphics View的各項


protected:
    void resizeEvent(QResizeEvent *event);//重定義了resizeEvent（）事件


private slots:
    void on_mouseMovePoint(QPoint point);


    void on_mouseClicked(QPoint point);


public:
explicit MainWindow(QWidget *parent = nullptr);
~MainWindow();


private:
Ui::MainWindow *ui;
};


#endif // MAINWINDOW_H


 

qwgraphicsview.h

#ifndef QWGRAPHICSVIEW_H
#define QWGRAPHICSVIEW_H
#include<QGraphicsView>
#include <QObject>
#include<qwgraphicsview.h>
#include"mainwindow.h"


/**
 * 從QGraphicsView類繼承一個類
 * 實現mouseMoveEvent和mousePressEvent事件
 * 把滑鼠事件轉換為訊號，在主程式中設計槽函式響應這些滑鼠事件
 **/
class QWGraphicsView : public QGraphicsView
{
    Q_OBJECT
protected:
    void mouseMoveEvent(QMouseEvent *event);
    void mousePressEvent(QMouseEvent *event);
public:
    QWGraphicsView(QWidget *parent=nullptr);


signals:
    void mouseMovePoint(QPoint point);
    void mouseClicked(QPoint point);


};


#endif // QWGRAPHICSVIEW_H


 

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include"qwgraphicsview.h"
#include<QFlags>
#include<QPen>
#include<QGraphicsEllipseItem>
#include<QBrush>


MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
labViewCord=new QLabel("View 座標：");
labViewCord->setMinimumWidth(150);
ui->statusBar->addWidget(labViewCord);
labSceneCord=new QLabel("Sence 座標:");
labSceneCord->setMinimumWidth(150);
ui->statusBar->addWidget(labSceneCord);
labItemCord=new QLabel("Item 座標：");
labItemCord->setMinimumWidth(150);
ui->statusBar->addWidget(labItemCord);
ui->View->setCursor(Qt::CrossCursor);//指標
ui->View->setMouseTracking(true);//該屬性用來設定某個控制元件是否被跟蹤軌跡。
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();
}


MainWindow::~MainWindow()
{
delete ui;
}
/**
 * @brief MainWindow::on_mouseClicked
 * @param point
 */
void MainWindow::on_mouseClicked(QPoint point)//滑鼠點選事件
{
    QPointF pointScene=ui->View->mapToScene(point);//轉換到Scene座標
    QGraphicsItem *item=nullptr;
    item=scene->itemAt(pointScene,ui->View->transform());//獲取游標下的圖形項
    if(item!=nullptr)//判斷是否有圖形項
    {
        QPointF pointItem=item->mapFromScene(pointScene);//圖形項的區域性座標
        labItemCord->setText(QString::asprintf("Item座標：%。0f，%。0f",pointItem.x(),pointItem.y()));
    }
}
/**
 * @brief MainWindow::on_mouseMovePoint
 * @param point
 */
void MainWindow::on_mouseMovePoint(QPoint point)
/*
 * 滑鼠移動事件
 * point是GraphicsView的座標
 * 是物理座標
 */
{
    labViewCord->setText(QString::asprintf("View座標：%d,%d",point.x(),point.y()));
    QPointF pointScene=ui->View->mapToScene(point);//轉換到Scene座標
    labSceneCord->setText(QString::asprintf("Sence座標：%.0f,%.0f",pointScene.x(),pointScene.y()));
}
/**
 * @brief MainWindow::resizeEvent
 * @param event
 */
void MainWindow::resizeEvent(QResizeEvent *event)//視窗變化時事件
{
    Q_UNUSED(event);
    ui->label->setText(QString::asprintf("Graphics View座標，左上角總是（0,0），寬度=%d，高度=%d",ui->View->width(),ui->View->height()));
    QRectF rectF=ui->View->sceneRect();//
    ui->label_2->setText(QString::asprintf("GraphcsView::sceneRect=(Left,Top,Width,Height)=%.0f,%.0f,%.0f,%.0f",
                                           rectF.left(),rectF.top(),rectF.width(),rectF.height()));
}
void MainWindow::iniGraphicsSystem()//構造Graphics View中的各項
{
    QRectF   rect(-200,-100,400,200);//左上角的座標，寬度，高度
    scene=new QGraphicsScene(rect);//scene邏輯座標系定義
    ui->View->setScene(scene);
    //畫一個矩形，大小等於scene
    QGraphicsRectItem *item=new QGraphicsRectItem(rect);
    item->setFlags(QGraphicsItem::ItemIsSelectable|//設定flags
                   //QGraphicsItem::ItemIsMovable|
                   QGraphicsItem::ItemIsFocusable);
    QPen pen;
    pen.setWidth(2);
    item->setPen(pen);
    scene->addItem(item);
    //畫一個位於scene中心的橢圓
    QGraphicsEllipseItem *item2=new QGraphicsEllipseItem(-100,-50,200,100);
    item2->setPos(0,0);
    item2->setBrush(QBrush(Qt::blue));
    item2->setFlags(QGraphicsItem::ItemIsSelectable|
                    QGraphicsItem::ItemIsMovable|
                    QGraphicsItem::ItemIsFocusable);
    scene->addItem(item2);
    //畫一個圓，中心位於scene的邊緣
    QGraphicsEllipseItem *item3=new QGraphicsEllipseItem(-50,-50,100,100);
    item3->setPos(rect.right(),rect.bottom());
    item3->setBrush(QBrush(Qt::red));
    item3->setFlags(QGraphicsItem::ItemIsSelectable|
                    QGraphicsItem::ItemIsMovable|
                    QGraphicsItem::ItemIsFocusable);
    scene->addItem(item3);
    scene->clearSelection();
}


 

qwgraphicsview.cpp

#include "qwgraphicsview.h"
#include<QPoint>
#include<QMouseEvent>
/**
 * @brief QWGraphicsView::QWGraphicsView
 * @param parent
 */
QWGraphicsView::QWGraphicsView(QWidget *parent):QGraphicsView(parent)
{


}
/**
 * @brief QWGraphicsView::mouseMoveEvent
 * @param event
 */
void QWGraphicsView::mouseMoveEvent(QMouseEvent *event)//滑鼠移動事件
{
    QPoint point=event->pos();//QGraphicsView的座標
    emit mouseMovePoint(point);//發射訊號
    QGraphicsView::mouseMoveEvent(event);
}
/**
 * @brief QWGraphicsView::mousePressEvent
 * @param event
 */
void QWGraphicsView::mousePressEvent(QMouseEvent *event)
{
    if(event->button()==Qt::LeftButton)//判斷按下滑鼠左鍵
    {
        QPoint point=event->pos();//獲取座標
        emit mouseClicked(point);//發射訊號
    }
    QGraphicsView::mousePressEvent(event);
}

執行結果