信号与槽的连接方式看起来会是这样的:
Qt5之前:
connect(sender,SIGNAL(signal), receiver, SLOT(slot));
Qt5开始:
connect(sender, &Sender::signal, receiver,&Receiver::slot);
前者:
sender和receiver是指向QObject的指针,signal和slot是不带参数的函数名。SIGNAL()宏和SLOT()宏会把他们的参数转换成相应的字符串。
后者:
(1)编译器,检查信号与槽是否存在,参数类型检查,Q_OBJECT宏是否存在
(2)信号可以和普通函数、类的普通成员函数、lambda函数连接(不在局限于信号和槽函数)
(3)参数可以是typedef的或者使用不同的namespace specifier
(4)可以允许一些自动类型的转换(即信号和槽函数类型不必完全匹配)
1、一个信号连接一个槽
connect(slider, &QSlider::valueChanged,spin_box, &QSpinBox::setValue);
2、一个信号连接多个槽
connect(slider,&QSlider::valueChanged, spin_box,&QSpinBox::setValue);
connect(slider, &QSlider::valueChanged,this, &QWidget::showValue);
3、多个信号连接同一个槽
connect(push_button, &QPushButton::clicked,this, &QWidget::show);
connect(tool_button, &QToolButton::clicked,this, &QWidget::show);
4、一个信号连接另一个信号
connect(push_button,&QPushlButton::clicked, this, &QWidget::buttonClicked);
5、断开链接
disconnect(push_button); //断开push_button的所有连接
disconnect(push_button,&QPushButton::clicked, this,&QWidget::show);//断开此信号连接的槽
再说说disconnect,见名知意,肯定与connect是相反的关系。
1、bool QObject::disconnect(const QObject * receiver,const char * method = 0) const
断开所有发送者的信号与接受者槽的连接
2、bool QObject::disconnect(const char * signal = 0, constQObject * receiver = 0, const char * method = 0) const
断开发送者和接受者的连接
3、bool QObject::disconnect(const QObject * sender, const char* signal, const QObject * receiver, const char * method)[static]
断开通常用于以下三种方式:
(1)断开所有连接到该对象的信号
disconnect(myObject, 0, 0, 0);
相当于非静态重载函数
myObject->disconnect();
(2)断开一切连接到特定信号:
disconnect(myObject, SIGNAL(mySignal()), 0, 0);
相当于非静态重载函数
myObject->disconnect(SIGNAL(mySignal()));
(3)断开一个特定的接收者:
disconnect(myObject, 0, myReceiver, 0);
相当于非静态重载函数
myObject->disconnect(myReceiver);
4、bool QObject::disconnect(const QObject * sender, constQMetaMethod & signal, const QObject * receiver, constQMetaMethod & method) [static]
5、bool QObject::disconnect(const QMetaObject::Connection &connection) [static]
6、bool QObject::disconnect(const QObject * sender,PointerToMemberFunction signal, const QObject * receiver,PointerToMemberFunction method) [static]
断开通常用于以下三种方式:
(1)断开所有连接到该对象的信号
disconnect(myObject, 0, 0, 0);
(2)断开一切连接到特定信号:
disconnect(myObject, &MyObject::mySignal(), 0, 0);
(3)断开一个特定的接收者:
disconnect(myObject, 0, myReceiver, 0);
(4)断开一个特定信号到特定槽的连接:
QObject::disconnect(lineEdit, &QLineEdit::textChanged, label, &QLabel::setText);
好了,这些都是最基本的应用。那么多个信号连接同一个槽的时候如何进行区分呢?
方法一:
typedefenum{
BUTTON_1,
BUTTON_2,
BUTTON_3,
BUTTON_4
}BUTTON;
push_button_1->setObjectName(QString::number(BUTTON_1,10));
push_button_2->setObjectName(QString::number(BUTTON_2,10));
tool_button_1->setObjectName(QString::number(BUTTON_3,10));
tool_button_2->setObjectName(QString::number(BUTTON_4,10));
connect(push_button_1,&QPushButton::clicked, this,&MyWidget::changeButton);
connect(push_button_2,&QPushButton::clicked, this, &MyWidget::changeButton);
connect(tool_button_1,&QToolButton::clicked, this, &MyWidget::changeButton);
connect(tool_button_2,&QToolButton::clicked, this,&MyWidget::changeButton);
void MyWidget::changeButton()
{
QObject*object = QObject::sender();
QPushButton *push_button = qobject_cast(object);
QToolButton *tool_button =qobject_cast<</span>QToolButton *>(object);
int index;
if(push_button)
{
QString object_name =push_button->objectName();
index =object_name.toInt();
}
elseif(tool_button )
{
QString object_name= tool_button->objectName();
index =object_name.toInt();
}
QStringinformation = QString("");
switch(index)
{
case BUTTON_1:
information = QString("clicked 1");
break;
case BUTTON_2:
information= QString("clicked 2");
break;
case BUTTON_3:
information = QString("clicked 3");
break;
case BUTTON_4:
information =QString("clicked 4");
break;
default:
information = QString("which is clicked?");
break;
}
QMessageBox::information(NULL,QString("Title"), information);
}
当然,setObjectName不是专门用来干这事的,也可以使用text进行区分或者其它方法,这里介绍的只是一种思路而已!
方法二:
QSignalMapper类可以简单的理解为信号的翻译和转发器,它可以把一个无参数的信号翻译成带int参数、QString参数、QObject*参数或者QWidget*参数的信号,并将之转发。
QSignalMapper *signal_mapper = new QSignalMapper(this);
connect(push_button_1, &QPushButton::clicked,signal_mapper, &QSignalMapper::map);
connect(push_button_2, &QPushButton::clicked,signal_mapper, &QSignalMapper::map);
connect(tool_button_1, &QToolButton::clicked,signal_mapper, &QSignalMapper::map);
connect(tool_button_2, &QToolButton::clicked,signal_mapper, &QSignalMapper::map);
signal_mapper->setMapping(push_button_1, QString::number(BUTTON_1,10));
signal_mapper->setMapping(push_button_2, QString::number(BUTTON_2,10));
signal_mapper->setMapping(tool_button_1, QString::number(BUTTON_3,10));
signal_mapper->setMapping(tool_button_2, QString::number(BUTTON_4,10));
connect(signal_mapper, &QSignalMapper::mapped,this, &MyWidget::changeButton);
void MyWidget::changeButton(QStringtext)
{
int index= text.toInt();
QStringinformation = QString("");
switch(index)
{
case BUTTON_1:
information = QString("clicked 1");
break;
case BUTTON_2:
information= QString("clicked 2");
break;
case BUTTON_3:
information = QString("clicked 3");
break;
case BUTTON_4:
information =QString("clicked 4");
break;
default:
information = QString("which is clicked?");
break;
}
QMessageBox::information(NULL,QString("Title"), information);
}
本人补充:方法三
利用QT5最新的信号-槽连接语法,以及C++11的lamba表达式,很容易实现槽函数的参数传递:
connect(ui.actionDefaultEngine, &QAction::triggered, this, [this](){return SelectSliceEngine(0,m_nSelectEngine); });
connect(ui.actionCuraEngine, &QAction::triggered, this, [this](){return SelectSliceEngine(1,m_nSelectEngine); });
connect(ui.actionSlicerEngine, &QAction::triggered, this, [this](){return SelectSliceEngine(2,m_nSelectEngine); });
上面是三个信号连接到同一个槽函数,利用传入的第一个参数表示不同的信号源,lambda表达式简单直观!
执行顺序
同一信号连接多个槽呢,槽函数执行没有绝对的先后顺序。
如:
connect(slider,&QSlider::valueChanged, spin_box,&QSpinBox::setValue);
connect(slider,&QSlider::valueChanged, this,&QWidget::showValue);
在Qt5之前,并不是setValue一定会比showValue先执行。
但在Qt5中,文档中这样介绍:
A signal can be connected to many slots and signals. Manysignals can be connected to one slot.
If a signal is connected to several slots, the slots areactivated in the same order in which the connections were made,when the signal is emitted.(一个信号连接多个槽,信号发射后,会按照链接顺序执行)。
经过简单测试的确如此:
connect(spin_box,&QSpinBox::valueChanged, this,&ListView::changeValue);
信号与槽连接看上去很正确,但是会出现如下错误:
意思就是说不能够明确的找出到底调用的是哪个信号(因为只有函数名称,并无详细参数说明),所以需加上参数说明,调用static_cast进行转换。 connect(spin_box,static_cast(&QSpinBox::valueChanged), this,&ListView::changeValue);
总结就到这里,都是很常用的东西,编程过程中多注意细节部分,多总结就好了。很多东西文档里都说的很清楚,write less,domore。。。