28——Extending QML – Signal Support Example
最后更新于：2022-04-01 07:22:08
本系列所有文章可以在这里查看[http://blog.csdn.net/cloud_castle/article/category/2123873](http://blog.csdn.net/cloud_castle/article/category/2123873)
接上文[Qt5官方demo解析集27——Extending QML - Attached Properties Example](http://blog.csdn.net/cloud_castle/article/details/37510123)
这个demo演示了为QML自定义类型添加信号的方法，这与[Qt5官方demo解析集16——Chapter 2: Connecting to C++ Methods and Signals](http://blog.csdn.net/cloud_castle/article/details/36882625)所介绍的差不多，鉴于例子的尺寸，可能那一篇要更清晰一些。
无论如何，我们还是要继续扩展这个BirthdayParty例程。我们为这个生日派对添加了一个“派对开始”的信号，并定义了一个函数用来发射这个信号。
由于person类依然没有改变，我们看看小小改动了的birthdayparty.h:
~~~
#ifndef BIRTHDAYPARTY_H
#define BIRTHDAYPARTY_H
#include <QObject>
#include <QDate>
#include <qqml.h>
#include "person.h"
class BirthdayPartyAttached : public QObject
{
Q_OBJECT
Q_PROPERTY(QDate rsvp READ rsvp WRITE setRsvp)
public:
BirthdayPartyAttached(QObject *object);
QDate rsvp() const;
void setRsvp(const QDate &);
private:
QDate m_rsvp;
};
class BirthdayParty : public QObject
{
Q_OBJECT
Q_PROPERTY(Person *host READ host WRITE setHost)
Q_PROPERTY(QQmlListProperty<Person> guests READ guests)
Q_CLASSINFO("DefaultProperty", "guests")
public:
BirthdayParty(QObject *parent = 0);
Person *host() const;
void setHost(Person *);
QQmlListProperty<Person> guests();
int guestCount() const;
Person *guest(int) const;
static BirthdayPartyAttached *qmlAttachedProperties(QObject *);
void startParty(); // 自定义函数，之所以不使用Q_INVOKABLE是因为该函数是在main.cpp而不是QML中被调用的
// ![0]
signals:
void partyStarted(const QTime &time); // 自定义信号
// ![0]
private:
Person *m_host;
QList<Person *> m_guests;
};
QML_DECLARE_TYPEINFO(BirthdayParty, QML_HAS_ATTACHED_PROPERTIES)
#endif // BIRTHDAYPARTY_H
~~~
birthdayParty.cpp:
~~~
#include "birthdayparty.h"
BirthdayPartyAttached::BirthdayPartyAttached(QObject *object)
: QObject(object)
{
}
QDate BirthdayPartyAttached::rsvp() const
{
return m_rsvp;
}
void BirthdayPartyAttached::setRsvp(const QDate &d)
{
m_rsvp = d;
}
BirthdayParty::BirthdayParty(QObject *parent)
: QObject(parent), m_host(0)
{
}
Person *BirthdayParty::host() const
{
return m_host;
}
void BirthdayParty::setHost(Person *c)
{
m_host = c;
}
QQmlListProperty<Person> BirthdayParty::guests()
{
return QQmlListProperty<Person>(this, m_guests);
}
int BirthdayParty::guestCount() const
{
return m_guests.count();
}
Person *BirthdayParty::guest(int index) const
{
return m_guests.at(index);
}
void BirthdayParty::startParty() // 该函数用来将当前时间作为信号参数发射出去
{
QTime time = QTime::currentTime();
emit partyStarted(time);
}
BirthdayPartyAttached *BirthdayParty::qmlAttachedProperties(QObject *object)
{
return new BirthdayPartyAttached(object);
}
~~~
example.qml:
~~~
import People 1.0
import QtQuick 2.0 // For QColor
BirthdayParty {
// ![0]
onPartyStarted: console.log("This party started rockin' at " + time); // 在QML中我们不需要额外对信号进行处理
// ![0] // 只需要关注与该信号对应的onXXX函数
// 当信号发出时该函数即被执行
host: Boy {
name: "Bob Jones"
shoe { size: 12; color: "white"; brand: "Nike"; price: 90.0 }
}
Boy {
name: "Leo Hodges"
BirthdayParty.rsvp: "2009-07-06"
shoe { size: 10; color: "black"; brand: "Reebok"; price: 59.95 }
}
Boy {
name: "Jack Smith"
shoe { size: 8; color: "blue"; brand: "Puma"; price: 19.95 }
}
Girl {
name: "Anne Brown"
BirthdayParty.rsvp: "2009-07-01"
shoe.size: 7
shoe.color: "red"
shoe.brand: "Marc Jacobs"
shoe.price: 699.99
}
// ![1]
}
// ![1]
~~~
main.cpp:
~~~
#include <QCoreApplication>
#include <QQmlEngine>
#include <QQmlComponent>
#include <QDebug>
#include "birthdayparty.h"
#include "person.h"
int main(int argc, char ** argv)
{
QCoreApplication app(argc, argv);
qmlRegisterType<BirthdayPartyAttached>();
qmlRegisterType<BirthdayParty>("People", 1,0, "BirthdayParty");
qmlRegisterType<ShoeDescription>();
qmlRegisterType<Person>();
qmlRegisterType<Boy>("People", 1,0, "Boy");
qmlRegisterType<Girl>("People", 1,0, "Girl");
QQmlEngine engine;
QQmlComponent component(&engine, QUrl("qrc:example.qml"));
BirthdayParty *party = qobject_cast<BirthdayParty *>(component.create());
if (party && party->host()) {
qWarning() << party->host()->name() << "is having a birthday!";
if (qobject_cast<Boy *>(party->host()))
qWarning() << "He is inviting:";
else
qWarning() << "She is inviting:";
for (int ii = 0; ii < party->guestCount(); ++ii) {
Person *guest = party->guest(ii);
QDate rsvpDate;
QObject *attached =
qmlAttachedPropertiesObject<BirthdayParty>(guest, false);
if (attached)
rsvpDate = attached->property("rsvp").toDate();
if (rsvpDate.isNull())
qWarning() << " " << guest->name() << "RSVP date: Hasn't RSVP'd";
else
qWarning() << " " << guest->name() << "RSVP date:" << qPrintable(rsvpDate.toString()); // 上文讨论了qPrintable的问题
}
party->startParty(); // 这里调用了发射信号函数，因此party开始时间将被打印在最后一行
} else {
qWarning() << component.errors();
}
return 0;
}
~~~
结果如图：
