添加，移动，调整大小，替换或删除qgraphicslineitem或其他图形对象

Question

同事警告我说我错了。这就是为什么我完全重新提出了我以前的问题。

a）最佳创建新行

b）如何可靠地选择20个其他人之间的特定行

c）如何最好地移动一条线的起点

d）如何最好地移动一条线的终点

e）如何最好地移动线

f）如何删除一行

文档和示例中描述了所有内容，但每个示例都为操作选择了不同的位置。有人使用视图，一些场景，另一个使用大部分内容。有人使用bouding rect，另一个没有，有人使用编辑模式而另一个没有等...

myscene.cpp

#include "myscene.h"
#include "myview.h"
#include "mymovingpoint.h"
#include <qgraphicsitem.h>
#include <qgraphicsview.h>
#include <qobject.h>
#include <qgraphicsview.h>
#include <qpoint.h>
#include <qmath.h>

/*
 *
 *
 */
myScene::myScene(QObject *parent)
    : QGraphicsScene(parent)
{
    myMode = myMode::InsertItem;
}
/*
 *
 *
 */
void myScene::mouseDoubleClickEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    # remove item added by clickevent, if doubleclicked
    if(line)
    {
        removeItem(line);
    }

    # if doubleclick and left button, select existing item
    if(mouseEvent->buttons().testFlag(Qt::LeftButton))
    {
        //QGraphicsItem *item = itemAt(mouseEvent->scenePos(), QTransform());
        # itemAt() returns only the object exactly under the mouse
        # function  getNearObject return object 3 points around
        QGraphicsItem *item = getNearObject(mouseEvent);
        if(item)
        {
            myMode = myMode::EditItem;

            myLineItem *tempLine = dynamic_cast<myLineItem*>(item);
            oldLine = line;
            line = tempLine;
            QColor myclr;
            myclr.setRgb(255,0,0,255);
            line->setPen(QPen(myclr, 2));
            line->addMovingPoints();
        }
        else
        {
            myMode = myMode::InsertItem;
        }
    }
}
/*
 *
 *
 */
#return nearest objects
QGraphicsItem* myScene::getNearObject(QGraphicsSceneMouseEvent *mouseEvent)
{
    int roundvalue = -3;
    int roundx;
    int roundy;

    QPointF pointf = mouseEvent->scenePos();
    QPointF pointtmp;

    roundx = roundvalue;
    roundy = roundvalue;
    while(roundy <= roundvalue*-1)
    {
        while(roundx <= roundvalue*-1)
        {
            pointtmp.setX(pointf.x()-roundx);
            pointtmp.setY(pointf.y()-roundy);
            QGraphicsItem *item = itemAt(pointtmp, QTransform());
            if(item)
            {
                return item;
            }
            roundx += 1;
        }
        roundx += roundvalue;
        roundy += 1;
    }
    return NULL;
}
/*
 *
 *
 */
void myScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if(mouseEvent->buttons().testFlag(Qt::LeftButton))
    {
        QGraphicsItem *item = itemAt(mouseEvent->scenePos(), QTransform());
        if(myMode == myMode::InsertItem)
        {
            if(oldLine)
            {
                myLineColor.setRgb(213, 182, 10, 255);
                oldLine->setPen(QPen(myLineColor, 2));
            }
        }

        if(myMode == myMode::EditItem)
        {
            myLineItem *tempLine = dynamic_cast<myLineItem*>(item);
            if(tempLine)
            {
                oldLine = line;
                line = tempLine;
                QColor myclr;
                myclr.setRgb(255,0,0,255);
                line->setPen(QPen(myclr, 2));
                myMovingPoint myPoint(line);
            }
        }
        else if(myMode == myMode::InsertItem)
        {
            oldLine = line;

            if(mouseEvent->modifiers() & Qt::ControlModifier)
            {
                line = new myLineItem(QLineF(toNearest5(mouseEvent->scenePos()), toNearest5(mouseEvent->scenePos())));
            }
            else
            {
                line = new myLineItem(QLineF(mouseEvent->scenePos(), mouseEvent->scenePos()));
            }

            myLineColor.setRgb(213, 182, 10, 255);
            line->setPen(QPen(myLineColor, 2));
        }
        else
        {
            QGraphicsScene::mousePressEvent(mouseEvent);
        }
    }
}
/*
 *
 *
 */
void myScene::mouseMoveEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    if(!items().contains(line))
    {
        addItem(line);
    }

    if(mouseEvent->buttons().testFlag(Qt::LeftButton))
    {
        QLineF newLine;
        if(myMode == myMode::InsertItem)
        {
            if(mouseEvent->modifiers() & Qt::ControlModifier)
            {
                newLine = QLineF(toNearest5(line->line().p1()), toNearest5(mouseEvent->scenePos()));
            }
            else
            {
                newLine = QLineF(line->line().p1(), mouseEvent->scenePos());
            }
            myLineColor.setRgb(213, 182, 10, 255);
            line->setLine(newLine);
            update();
        }
        else if(myMode == myMode::EditItem)
        {
            QLineF newLine = QLineF(line->line().p1(), mouseEvent->scenePos());
            line->setLine(newLine);
            update();
        }
    }
    QGraphicsScene::mouseMoveEvent(mouseEvent);
}
/*
 *
 *
 */
void myScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
    myMode = myMode::InsertItem;
    QGraphicsScene::mouseReleaseEvent(mouseEvent);
}
/*
 *
 *
 */
void myScene::keyPressEvent(QKeyEvent * keyEvent)
{
    if(keyEvent->key() == Qt::Key_Delete)
    {
        if(line)
        {
            removeItem(line);
        }
    }
}
/*
 *
 *
 */
QPointF myScene::toNearest5(QPointF i)
{
    int shift = 10;

    int r = i.x();
    int s = i.y();

    r = (i.x()+5.0)/10;
    s = (i.y()+5.0)/10;

    r = r*10;
    s = s*10;

    QPointF output = QPointF(r, s);
    return (output);
}

mysceneview.cpp

#include "myview.h"
#include <qmath.h>
#include <qmatrix.h>


myView::myView(QGraphicsScene *scene, QWidget *parent)
    : QGraphicsView(scene, parent)
{
}


void myView::keyPressEvent(QKeyEvent *event)
{
    QGraphicsView::keyPressEvent(event);
}


void myView::keyReleaseEvent(QKeyEvent *event)
{
    QGraphicsView::keyReleaseEvent(event);
}

void myView::enterEvent(QEvent *event)
{
    viewport()->setCursor(Qt::ArrowCursor);
    QGraphicsView::enterEvent(event);
}


void myView::mousePressEvent(QMouseEvent* event)
{
    if (event->modifiers() & Qt::ControlModifier)
    {
        viewport()->setCursor(Qt::ArrowCursor);
        _lastPos = QPoint(event->pos());
        //_lastPos = QPoint(event->pos().x()-event->pos().x()%5, event->pos().y()-event->pos().y()%5);
    }
    else
    {
        viewport()->setCursor(Qt::ArrowCursor);
        _lastPos = event->pos();
    }
    QGraphicsView::mousePressEvent(event);
}


void myView::mouseMoveEvent(QMouseEvent* event)
{
    viewport()->setCursor(Qt::ArrowCursor);

    if (event->buttons().testFlag(Qt::RightButton))
    {
        QScrollBar *hBar = horizontalScrollBar();
        QScrollBar *vBar = verticalScrollBar();
        QPoint delta = event->pos() - _lastPos;
        _lastPos = event->pos();
        hBar->setValue(hBar->value() + (isRightToLeft() ? delta.x() : -delta.x()));
        vBar->setValue(vBar->value() - delta.y());
        //event->ignore();
    }
    QGraphicsView::mouseMoveEvent(event);
}


void myView::mouseReleaseEvent(QMouseEvent* event)
{
    viewport()->setCursor(Qt::ArrowCursor);
    QGraphicsView::mouseReleaseEvent(event);
}



#if QT_CONFIG(wheelevent)
void myView::wheelEvent(QWheelEvent *e)
{
        if (e->delta() > 0)
        {
            x=x+0.1;
            qreal scale = x;

            QMatrix matrix;
            matrix.scale(scale, scale);

            setMatrix(matrix);
            //zoomIn(6);
        }
        else
        {
            x=x-0.1;
            qreal scale = x;

            QMatrix matrix;
            matrix.scale(scale, scale);

            setMatrix(matrix);
            //zoomOut(6);
        }
        e->accept();
}
#endif