QGraphicsXXXItem
不支持 q-properties,因此不能QPropertyAnimation
直接使用。所以解决方案是创建一个继承QObject
and的类QGraphicsLineItem
,另外我们必须添加一个 q-property 来处理与行关联的p2
位置,QLineF
如下所示:
lineitem.h
#ifndef LINEITEM_H
#define LINEITEM_H
#include <QGraphicsLineItem>
#include <QObject>
class LineItem: public QObject, public QGraphicsLineItem {
Q_OBJECT
Q_PROPERTY(QPointF p1 READ p1 WRITE setP1)
Q_PROPERTY(QPointF p2 READ p2 WRITE setP2)
public:
using QGraphicsLineItem::QGraphicsLineItem;
QPointF p1() const {
return line().p1();
}
void setP1(const QPointF & p){
QLineF l = line();
l.setP1(p);
setLine(l);
}
QPointF p2() const {
return line().p2();
}
void setP2(const QPointF & p){
QLineF l = line();
l.setP2(p);
setLine(l);
}
};
#endif // LINEITEM_H
主文件
#include "lineitem.h"
#include <QApplication>
#include <QGraphicsView>
#include <QPropertyAnimation>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QGraphicsScene scene(-100, -100, 200, 200);
QGraphicsView view(&scene);
QGraphicsLineItem *item = scene.addLine(QLine(0, 100, 100, 0));
item->setPen(QPen(Qt::red, 5));
LineItem *lineItem = new LineItem(QLineF(QPointF(0, 0), QPointF(0, 100)));
scene.addItem(lineItem);
lineItem->setPen(QPen(Qt::green, 2));
QPropertyAnimation *anim = new QPropertyAnimation(lineItem, "p2");
anim->setStartValue(QPointF(0, 100));
anim->setEndValue(QPointF(100, 0));
anim->setDuration(2000);
anim->start();
view.resize(640, 480);
view.show();
return a.exec();
}
另一种方法是使用 QVariantAnimation:
#include <QApplication>
#include <QGraphicsView>
#include <QPropertyAnimation>
#include <QGraphicsLineItem>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QGraphicsScene scene(-100, -100, 200, 200);
QGraphicsView view(&scene);
scene.addLine(QLine(0, 100, 100, 0), QPen(Qt::green));
QGraphicsLineItem *item = scene.addLine(QLine(0, 0, 0, 100));
item->setPen(QPen(Qt::red, 5));
QVariantAnimation * anim = new QVariantAnimation(&scene);
anim->setStartValue(QPointF(0, 100));
anim->setEndValue(QPointF(100, 0));
anim->setDuration(2000);
anim->start();
QObject::connect(anim, &QVariantAnimation::valueChanged, [item](const QVariant & val){
QLineF l = item->line();
l.setP2(val.toPointF());
item->setLine(l);
});
view.resize(640, 480);
view.show();
return a.exec();
}