我曾经遇到过你所遇到的问题,并希望在Anthony非常好的回答上补充一些见解。这里是我编写的一个示例,展示了可以使用鼠标事件和键盘事件实现的一些功能。
请注意,事件不会传播到QGraphicsItemGroup
或QList<QGraphicsItem>
中的QGraphicsItem
(我花了一段时间才弄清楚这一点)。
#include <QtGui>
#include <QGraphicsRectItem>
#include <QGraphicsView>
#include <QApplication>
#include <QGraphicsSceneMouseEvent>
class CustomItem : public QGraphicsEllipseItem
{
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event)
{
if(event->button() == Qt::LeftButton) {
if(event->modifiers() == Qt::ShiftModifier) {
qDebug() << "Custom item left clicked with shift key.";
setSelected(true);
} else if(event->modifiers() == Qt::AltModifier){
qDebug() << "Custom item left clicked with alt key.";
double radius = boundingRect().width() / 2.0;
_center = QPointF(boundingRect().topLeft().x() + pos().x() + radius, boundingRect().topLeft().y() + pos().y() + radius);
QPointF pos = event->scenePos();
qDebug() << boundingRect() << radius << this->pos() << pos << event->pos();
double dist = sqrt(pow(_center.x()-pos.x(), 2) + pow(_center.y()-pos.y(), 2));
if(dist / radius > 0.8) {
qDebug() << dist << radius << dist / radius;
_isResizing = true;
} else {
_isResizing = false;
}
} else {
qDebug() << "Custom item left clicked.";
QGraphicsItem::mousePressEvent(event);
event->accept();
}
} else if(event->button() == Qt::RightButton) {
qDebug() << "Custom item right clicked.";
event->ignore();
}
}
void mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
if(event->modifiers() == Qt::AltModifier && _isResizing){
QPointF pos = event->scenePos();
double dist = sqrt(pow(_center.x()-pos.x(), 2) + pow(_center.y()-pos.y(), 2));
setRect(_center.x()-this->pos().x()-dist, _center.y()-this->pos().y()-dist, dist*2, dist*2);
} else if(event->modifiers() != Qt::AltModifier) {
qDebug() << "Custom item moved.";
QGraphicsItem::mouseMoveEvent(event);
qDebug()<<"moved"<<pos();
}
}
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
if(event->modifiers() == Qt::AltModifier && _isResizing) {
_isResizing = false;
} else if(event->modifiers() != Qt::ShiftModifier) {
QGraphicsItem::mouseReleaseEvent(event);
}
}
int type() const
{
return UserType+1;
}
private:
QPointF _center;
bool _isResizing;
};
class CustomScene : public QGraphicsScene
{
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event)
{
qDebug() << "Custom scene clicked.";
QGraphicsScene::mousePressEvent(event);
if(!event->isAccepted()) {
if(event->button() == Qt::LeftButton) {
QPointF pt = event->scenePos();
CustomItem * item = new CustomItem();
item->setRect(pt.x()-25, pt.y()-25, 50, 50);
item->setFlags(QGraphicsItem::ItemIsSelectable|
QGraphicsItem::ItemIsMovable);
addItem(item);
} else if(event->button() == Qt::RightButton) {
QGraphicsItem * itemToRemove = NULL;
foreach(auto item, items(event->scenePos())) {
if(item->type() == QGraphicsItem::UserType+1) {
itemToRemove = item;
break;
}
}
if(itemToRemove) {
removeItem(itemToRemove);
}
}
}
}
void mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
qDebug() << "Custom scene moved.";
QGraphicsScene::mouseMoveEvent(event);
}
void keyPressEvent(QKeyEvent * event) {
if(event->key() == Qt::Key_Backspace) {
qDebug() << "selected items" << selectedItems().size();
while(!selectedItems().isEmpty()) {
removeItem(selectedItems().front());
}
} else {
QGraphicsScene::keyPressEvent(event);
}
}
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
CustomItem item;
item.setRect(20, 20, 60, 60);
item.setFlags(QGraphicsItem::ItemIsSelectable|
QGraphicsItem::ItemIsMovable);
CustomScene scene;
scene.setSceneRect(0, 0, 500, 500);
scene.addItem(&item);
QGraphicsView view;
view.setScene(&scene);
view.show();
return a.exec();
}
希望这也能有所帮助!
QGraphicsItem :: boundingRect()
返回的矩形不正确,或者如果你重新实现了QGraphicsItem::shape()
,它也不正确。 - AnthonyQGraphicsSceneMouseEvent
。我一直在寻找QMouseEvent
作为参数,因为QGraphicsView
的重写使用它们。我没有注意到对于QGraphicsItem
来说它们是不同的。你的例子指出了这一点。我感到很尴尬。 :) - Almomouse...Event()
,所以我想补充一下(我认为)如果你将mouse...Event
方法添加到视图和场景类中,它不会起作用,应该是其中之一。在我的情况下,视图捕获了它,并没有将其传递给继承的QGRectItem,但现在我解决了这个问题。谢谢大家! - user12927872