在两个组件之间生成连线

connection.cpp

@@ -0,0 +1,20 @@
+#include "connection.h"
+
+#include <QPen>
+
+Connection::Connection(Item* from, Item::AnchorType fromType,
+                       Item* to, Item::AnchorType toType, QGraphicsItem* parent)
+    : QGraphicsLineItem(parent),
+      from_(from), to_(to), fromType_(fromType), toType_(toType)
+{
+    setZValue(-1); // 在图元之下
+    setPen(QPen(Qt::black, 2));
+    from_->addConnection(this);
+    to_->addConnection(this);
+    updatePosition();
+}
+
+void Connection::updatePosition()
+{
+    setLine(QLineF(from_->anchorPos(fromType_), to_->anchorPos(toType_)));
+}

connection.h

@@ -0,0 +1,19 @@
+#ifndef CONNECTION_H
+#define CONNECTION_H
+
+#include <QGraphicsLineItem>
+#include "item.h"
+
+class Connection : public QGraphicsLineItem
+{
+public:
+    Connection(Item* from, Item::AnchorType fromType,
+               Item* to, Item::AnchorType toType, QGraphicsItem* parent = nullptr);
+
+    void updatePosition();
+
+    Item *from_, *to_;
+    Item::AnchorType fromType_, toType_;
+};
+
+#endif // CONNECTION_H

editor.pro

@@ -16,12 +16,14 @@ DEFINES += QT_DEPRECATED_WARNINGS
 #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
 
 SOURCES += \
+    connection.cpp \
     item.cpp \
     main.cpp \
     mainwindow.cpp \
     mygraphicsview.cpp
 
 HEADERS += \
+    connection.h \
     item.h \
     mainwindow.h \
     mygraphicsview.h

item.cpp

@@ -1,4 +1,5 @@
 #include "item.h"
+#include "connection.h"
 #include <QPainter>
 #include <QStyleOptionGraphicsItem>
 
@@ -17,17 +18,59 @@ Item::Item(const QString &type, QGraphicsItem *parent)
 
 QRectF Item::boundingRect() const
 {
-    return QRectF(0, 0, 80, 40);
+    return QRectF(-5, -5, 90, 50);
 }
 
 void Item::paint(QPainter *painter,
                  const QStyleOptionGraphicsItem *,
                  QWidget *)
 {
+    QRectF r = boundingRect().adjusted(5, 5, -5, -5); // 图元主体
     painter->setBrush(color_.lighter(150));
     painter->setPen(QPen(color_, 2));
-    painter->drawRoundedRect(boundingRect(), 5, 5);
+    painter->drawRoundedRect(r, 5, 5);
+
+    // 画锚点
+    painter->setBrush(Qt::darkGray);
+    painter->setPen(Qt::NoPen);
+    painter->drawEllipse(QPointF(r.left(), r.center().y()), 5, 5);   // 左锚点
+    painter->drawEllipse(QPointF(r.right(), r.center().y()), 5, 5);  // 右锚点
 
     painter->setPen(Qt::black);
-    painter->drawText(boundingRect(), Qt::AlignCenter, type_);
+    painter->drawText(r, Qt::AlignCenter, type_);
+}
+
+QPointF Item::anchorPos(AnchorType anc) const
+{
+    QRectF r = boundingRect();
+    switch (anc) {
+    case Left:  return mapToScene(QPointF(r.left(), r.center().y()));
+    case Right: return mapToScene(QPointF(r.right(), r.center().y()));
+    }
+    return QPointF();
+}
+
+void Item::addConnection(Connection* conn)
+{
+    if (!connections_.contains(conn))
+        connections_.append(conn);
+}
+
+void Item::removeConnection(Connection* conn)
+{
+    connections_.removeAll(conn);
+}
+
+QList<Connection *> Item::connections()
+{
+    return connections_;
+}
+
+QVariant Item::itemChange(GraphicsItemChange change, const QVariant &value)
+{
+    if (change == QGraphicsItem::ItemPositionChange) {
+        for (Connection* conn : connections_)
+            conn->updatePosition();
+    }
+    return QGraphicsObject::itemChange(change, value);
 }

item.h

@@ -2,11 +2,16 @@
 #define ITEM_H
 
 #include <QGraphicsObject>
+#include <QColor>
+#include <QList>
+
+class Connection;
 
 class Item : public QGraphicsObject
 {
     Q_OBJECT
 public:
+    enum AnchorType { Left, Right };
     explicit Item(const QString &type, QGraphicsItem *parent = nullptr);
 
     QRectF boundingRect() const override;
@@ -14,9 +19,19 @@ public:
                const QStyleOptionGraphicsItem *option,
                QWidget *widget) override;
 
+    QPointF anchorPos(AnchorType type) const;
+    void addConnection(Connection* conn);
+    void removeConnection(Connection* conn);
+    QList<Connection*> connections();
+
+protected:
+    QVariant itemChange(GraphicsItemChange change, const QVariant &value) override;
+
 private:
     QString type_;
     QColor  color_;
+    QList<Connection*> connections_;
+
 };
 
 #endif // ITEM_H

mainwindow.cpp

@@ -19,10 +19,7 @@ MainWindow::MainWindow(QWidget *parent)
     /* 1. 场景 */
     m_scene = new QGraphicsScene(this);
     ui->graphicsView->setScene(m_scene);
-    ui->graphicsView->setRenderHint(QPainter::Antialiasing);
     ui->graphicsView->setSceneRect(0, 0, 800, 600);
-    ui->graphicsView->setAcceptDrops(true);
-    ui->graphicsView->setFocus();
 
     /* 2. 列表 */
     ui->listWidget->setViewMode(QListView::IconMode);

mainwindow.ui

@@ -19,8 +19,8 @@
      <rect>
       <x>20</x>
       <y>10</y>
-      <width>161</width>
-      <height>381</height>
+      <width>171</width>
+      <height>491</height>
      </rect>
     </property>
    </widget>
@@ -29,8 +29,8 @@
      <rect>
       <x>210</x>
       <y>10</y>
-      <width>791</width>
-      <height>381</height>
+      <width>871</width>
+      <height>491</height>
      </rect>
     </property>
     <property name="dragMode">

mygraphicsview.cpp

@@ -10,7 +10,7 @@ MyGraphicsView::MyGraphicsView(QWidget *parent)
     setAcceptDrops(true);
     viewport()->setAcceptDrops(true);
     setRenderHint(QPainter::Antialiasing);
-    setFocusPolicy(Qt::StrongFocus); // 让view能接收键盘事件
+    setFocusPolicy(Qt::StrongFocus);
 }
 
 void MyGraphicsView::dragEnterEvent(QDragEnterEvent *event)
@@ -51,9 +51,18 @@ void MyGraphicsView::dropEvent(QDropEvent *event)
 void MyGraphicsView::keyPressEvent(QKeyEvent *event)
 {
     if (event->key() == Qt::Key_Delete && scene()) {
-        // 删除所有被选中的图元
         QList<QGraphicsItem*> selectedItems = scene()->selectedItems();
         for (QGraphicsItem* item : selectedItems) {
+            // 如果是Item，顺便删除其连线
+            if (auto node = dynamic_cast<Item*>(item)) {
+                QList<Connection*> conns = node->connections();
+                for (Connection* conn : conns) {
+                    scene()->removeItem(conn);
+                    conn->from_->removeConnection(conn);
+                    conn->to_->removeConnection(conn);
+                    delete conn;
+                }
+            }
             scene()->removeItem(item);
             delete item;
         }
@@ -61,3 +70,83 @@ void MyGraphicsView::keyPressEvent(QKeyEvent *event)
         QGraphicsView::keyPressEvent(event);
     }
 }
+
+// ----------- 连线交互 ------------
+
+Item* MyGraphicsView::anchorItemAt(const QPoint& viewPos, Item::AnchorType& anchorType)
+{
+    QPointF scenePos = mapToScene(viewPos);
+    for (QGraphicsItem* item : scene()->items(scenePos)) {
+        if (Item* node = dynamic_cast<Item*>(item)) {
+            QRectF r = node->boundingRect();
+            QPointF local = node->mapFromScene(scenePos);
+            if (QLineF(local, QPointF(r.left(), r.center().y())).length() < 10) {
+                anchorType = Item::Left;
+                return node;
+            }
+            if (QLineF(local, QPointF(r.right(), r.center().y())).length() < 10) {
+                anchorType = Item::Right;
+                return node;
+            }
+        }
+    }
+    return nullptr;
+}
+
+void MyGraphicsView::mousePressEvent(QMouseEvent *event)
+{
+    if (event->button() == Qt::LeftButton) {
+        Item::AnchorType anchor;
+        Item* node = anchorItemAt(event->pos(), anchor);
+        if (node) {
+            drawingConnection_ = true;
+            startItem_ = node;
+            startAnchor_ = anchor;
+            tempLine_ = scene()->addLine(QLineF(node->anchorPos(anchor), mapToScene(event->pos())),
+                                         QPen(Qt::darkGray, 2, Qt::DashLine));
+            return;
+        }
+    }
+    QGraphicsView::mousePressEvent(event);
+}
+
+void MyGraphicsView::mouseMoveEvent(QMouseEvent *event)
+{
+    if (drawingConnection_ && tempLine_) {
+        QLineF l = tempLine_->line();
+        l.setP2(mapToScene(event->pos()));
+        tempLine_->setLine(l);
+        return;
+    }
+    QGraphicsView::mouseMoveEvent(event);
+}
+
+void MyGraphicsView::mouseReleaseEvent(QMouseEvent *event)
+{
+    if (drawingConnection_ && tempLine_) {
+        // 检查鼠标释放点是否在某个Item boundingRect内
+        QPointF scenePos = mapToScene(event->pos());
+        for (QGraphicsItem* item : scene()->items(scenePos)) {
+            if (Item* node = dynamic_cast<Item*>(item)) {
+                QRectF r = node->boundingRect();
+                QPointF local = node->mapFromScene(scenePos);
+                // 计算落点距离左右端点
+                double distLeft = QLineF(local, QPointF(r.left(), r.center().y())).length();
+                double distRight = QLineF(local, QPointF(r.right(), r.center().y())).length();
+                Item::AnchorType anchor = (distLeft < distRight) ? Item::Left : Item::Right;
+                // 生成连线
+                Connection* conn = new Connection(startItem_, startAnchor_, node, anchor);
+                scene()->addItem(conn);
+                break;
+            }
+        }
+        // 清除临时线
+        scene()->removeItem(tempLine_);
+        delete tempLine_;
+        tempLine_ = nullptr;
+        drawingConnection_ = false;
+        startItem_ = nullptr;
+        return;
+    }
+    QGraphicsView::mouseReleaseEvent(event);
+}

mygraphicsview.h

@@ -6,7 +6,9 @@
 #include <QDragEnterEvent>
 #include <QMimeData>
 #include <QKeyEvent>
+#include <QMouseEvent>
 #include "item.h"
+#include "connection.h"
 
 class MyGraphicsView : public QGraphicsView
 {
@@ -16,9 +18,21 @@ public:
 
 protected:
     void dragEnterEvent(QDragEnterEvent *event) override;
-    void dropEvent(QDropEvent *event) override;
     void dragMoveEvent(QDragMoveEvent *event) override;
+    void dropEvent(QDropEvent *event) override;
     void keyPressEvent(QKeyEvent *event) override;
+
+    void mousePressEvent(QMouseEvent *event) override;
+    void mouseMoveEvent(QMouseEvent *event) override;
+    void mouseReleaseEvent(QMouseEvent *event) override;
+
+private:
+    Item* anchorItemAt(const QPoint& viewPos, Item::AnchorType& anchorType);
+
+    bool drawingConnection_ = false;
+    Item* startItem_ = nullptr;
+    Item::AnchorType startAnchor_;
+    QGraphicsLineItem* tempLine_ = nullptr;
 };
 
 #endif // MYGRAPHICSVIEW_H