Question

我有一个12 * 4网格的场景和QGraphicsItems块，当我右键单击块时我有一个上下文菜单我可以在块中添加图标我不知道如何让这些图标可以拖动到图形场景中的其他块，我知道有＆＃34;可拖动图标示例＆＃34;但是如何将该代码实现为图形场景。

这是mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QGraphicsPathItem>
class QGraphicsSceneMouseEvent;
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
bool eventFilter(QObject *, QEvent *);
~MainWindow();

private slots:
void showContextMenu(const QPoint&);
void addPixBlock();

private:
Ui::MainWindow *ui;
QGraphicsScene *scene;
QGraphicsItem *itemAt(const QPointF&);

int x;
int y;

QMenu *Menu;
QMenu *Submenu;
QAction *Picture;
QGraphicsPixmapItem* pix;
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "block.h"
#include <QGraphicsScene>
#include <QGraphicsSceneMouseEvent>
#include <QDebug>
#include <QPainter>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
scene = new QGraphicsScene(this) ;
for(int row=-4;row<8;++row)
  for(int column=0;column<4;++column)
{
  Block *b = new Block;
  scene->addItem(b);
  b->setPos(row* 95,column*85);
}
ui->graphicsView->setScene(scene);
scene->installEventFilter(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
QGraphicsItem* MainWindow::itemAt(const QPointF &pos)
{
QList<QGraphicsItem*> items = scene->items(QRectF(pos - QPointF(1,1), 
QSize(3,3)));

foreach(QGraphicsItem *item, items)
     if (item->type() > QGraphicsItem::UserType)
     return item;
 return 0;
  }
 bool MainWindow::eventFilter(QObject *o, QEvent *e)
  {
 QGraphicsSceneMouseEvent *me = (QGraphicsSceneMouseEvent*) e;

 switch ((int) e->type()){

 case QEvent::GraphicsSceneMousePress:{

 switch ((int) me->button()){

  case Qt::RightButton:{

     QGraphicsItem *item = itemAt(me->scenePos());

     if (item && item->type() == Block::Type){
         x=item->scenePos().x();
         y=item->scenePos().y();
        showContextMenu(item->scenePos().toPoint());
      }
   break;
  }
  }
  break;
  }
 }
 return QObject::eventFilter(o, e);
 }
void MainWindow::showContextMenu(const QPoint &pos)
{
Menu= new QMenu("Menu");
Submenu=Menu->addMenu(QIcon(":/img/pix.png"),"Pix");
Picture =Submenu->addAction(QIcon(":/img/pix.png"),"Pix");
connect(Picture, SIGNAL(triggered()), this, SLOT(addPixBlock()));
Menu->exec(QCursor::pos());
}
void MainWindow::addPixBlock()
{
QPixmap pixmap(":/img/pix.png");
pix = scene->addPixmap(pixmap.scaled(70,50));
pix->setPos(x,y);
}

block.h

#ifndef BLOCK_H
#define BLOCK_H
#include <QGraphicsPathItem>
class QGraphicsSceneMouseEvent;
class Block : public QGraphicsPathItem
{
public:
enum { Type = QGraphicsItem::UserType + 3 };
int type() const { return Type; }
Block(QGraphicsItem *parent = 0);
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget 
*widget);
bool eventFilter(QObject *, QEvent *);
};
#endif // BLOCK_H

Block.cpp

#include "block.h"
#include <QPainter>
#include <QtWidgets>
class QGraphicsSceneMouseEvent;
Block::Block(QGraphicsItem *parent)
         : QGraphicsPathItem(parent)
{
QPainterPath p;
//<->,|,<->,|,roundness
p.addRoundedRect(0,0,80,50, 5, 5);
setPath(p);
setAcceptDrops(true);
setAcceptedMouseButtons(Qt::LeftButton);
}
void Block::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, 
QWidget *widget)
{
Q_UNUSED(option)
Q_UNUSED(widget)
painter->setPen(QPen(QColor(67, 141, 220)));
painter->setBrush(QColor(67, 141, 220,100));
painter->drawPath(path());
}

Answer 1

首先，如果您想将QGraphicsPixmapItem放在另一个项目的顶部，更好的选择是将其设置为parentItem。

另一方面，我们可以使用事件过滤器，但在这种情况下更好的选择是实现自定义QGraphicsScene，当按下左键时，它允许拖动项目，为此我们使用{ {1}}我们传递项目的数据，然后我们覆盖事件QDrag，我们将获取该项目并建立新的父项。

<强> graphicsscene.h

dropEvent

<强> graphicsscene.cpp

#ifndef GRAPHICSSCENE_H
#define GRAPHICSSCENE_H

#include <QGraphicsScene>

class QMenu;
class QAction;

class GraphicsScene : public QGraphicsScene
{
public:
    using QGraphicsScene::QGraphicsScene;

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event) override;
    void dropEvent(QGraphicsSceneDragDropEvent *event) override;

private:
    QGraphicsPixmapItem *findPixmapItem(QGraphicsItem *item);
    void createDrag(const QPointF &pos, QWidget *widget, QGraphicsItem *item);
    void showContextMenu(const QPointF &pos);
    void addPixBlock(QGraphicsItem *item);

    QMenu *menu;
    QMenu *submenu;
    QAction *picture;
    QGraphicsPixmapItem *pix;
};

#endif // GRAPHICSSCENE_H

然后我们建立新场景并添加#include "graphicsscene.h" #include <QDrag> #include <QGraphicsItem> #include <QGraphicsSceneMouseEvent> #include <QMenu> #include <QMimeData> #include <QWidget> void GraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *event) { auto its = items(QRectF(event->scenePos() - QPointF(1,1), QSize(3,3))); auto val = std::find_if(its.constBegin(), its.constEnd(), [](auto const& it){ return it->type() > QGraphicsItem::UserType; }); if(val == its.constEnd()) return; if(event->button() == Qt::RightButton){ showContextMenu(event->scenePos()); } else{ createDrag(event->scenePos(), event->widget(), *val); } } void GraphicsScene::dropEvent(QGraphicsSceneDragDropEvent *event) { QByteArray byteArray = event->mimeData()->data("Item"); QGraphicsPixmapItem * item = *reinterpret_cast<QGraphicsPixmapItem**>(byteArray.data()); QGraphicsItem *item_parent = itemAt(event->scenePos(), QTransform()); item->setParentItem(item_parent); } QGraphicsPixmapItem *GraphicsScene::findPixmapItem(QGraphicsItem *item){ auto chs = item->childItems(); auto val = std::find_if(chs.constBegin(), chs.constEnd(), [](auto const& it){ return static_cast<QGraphicsPixmapItem *>(it) != Q_NULLPTR; }); return val == chs.constEnd() ? Q_NULLPTR : static_cast<QGraphicsPixmapItem *>(*val); } void GraphicsScene::createDrag(const QPointF &pos, QWidget *widget, QGraphicsItem *item){ QGraphicsPixmapItem *pix = findPixmapItem(item); if(pix == Q_NULLPTR) return; QByteArray byteArray(reinterpret_cast<char*>(&pix),sizeof(QGraphicsPixmapItem*)); QDrag *drag = new QDrag(widget); QMimeData * mimeData = new QMimeData; mimeData->setData("Item",byteArray); drag->setMimeData(mimeData); drag->setHotSpot(pos.toPoint()-pix->scenePos().toPoint()); drag->setPixmap(pix->pixmap()); drag->start(); } void GraphicsScene::showContextMenu(const QPointF &pos) { QGraphicsItem *item = itemAt(pos, QTransform()); menu= new QMenu("Menu"); submenu = menu->addMenu(QIcon(":/img/pix.png"),"Pix"); picture = submenu->addAction(QIcon(":/img/pix.png"),"Pix"); connect(picture, &QAction::triggered, [item, this](){ addPixBlock(item); }); menu->exec(QCursor::pos()); } void GraphicsScene::addPixBlock(QGraphicsItem *item) { if(findPixmapItem(item)) return; QPixmap pixmap(":/img/pix.png"); pix = addPixmap(pixmap.scaled(70,50)); if(pix->parentItem() != item) pix->setParentItem(item); } s。

完整示例可在以下link

中找到

可拖动的像素图在QGraphicsScene的图形项目中

1 个答案: