Qt5学习笔记 | 信号槽

￡神魔★判官ぃ 2021-09-30 15:28 311阅读 0赞

在 Qt 5 中，`QObject::connect()`有五个重载：

QMetaObject::Connection connect(const QObject *, const char *,
                                    const QObject *, const char *,
                                    Qt::ConnectionType);
     
    QMetaObject::Connection connect(const QObject *, const QMetaMethod &,
                                    const QObject *, const QMetaMethod &,
                                    Qt::ConnectionType);
     
    QMetaObject::Connection connect(const QObject *, const char *,
                                    const char *,
                                    Qt::ConnectionType) const;
     
    QMetaObject::Connection connect(const QObject *, PointerToMemberFunction,
                                    const QObject *, PointerToMemberFunction,
                                    Qt::ConnectionType)
     
    QMetaObject::Connection connect(const QObject *, PointerToMemberFunction,
                                    Functor);

最常用的一般形式：

1 connect(sender,   signal,   receiver,   slot);

sender：发出信号的对象，类型为QObject\*

signal：发出的信号，类型为const char\*

receiver：接收信号的对象，类型为QObject\*

slot：接收信号后调用的函数（槽函数），类型为const char\*

注意：槽函数的参数类型要和信号的一致，参数数量小于等于信号数量。

自定义槽函数：

1 #include <QObject>
     2  
     3 // newspaper.h
     4 class Newspaper : public QObject
     5 {
     6     Q_OBJECT
     7 public:
     8     Newspaper(const QString & name) :
     9         m_name(name)
    10     {
    11     }
    12  
    13     void send()
    14     {
    15         emit newPaper(m_name);
    16     }
    17  
    18 signals:
    19     void newPaper(const QString &name);
    20  
    21 private:
    22     QString m_name;
    23 };
    24  
    25 // reader.h
    26 #include <QObject>
    27 #include <QDebug>
    28  
    29 class Reader : public QObject
    30 {
    31     Q_OBJECT
    32 public:
    33     Reader() {}
    34  
    35     void receiveNewspaper(const QString & name)
    36     {
    37         qDebug() << "Receives Newspaper: " << name;
    38     }
    39 };
    40  
    41 // main.cpp
    42 #include <QCoreApplication>
    43  
    44 #include "newspaper.h"
    45 #include "reader.h"
    46  
    47 int main(int argc, char *argv[])
    48 {
    49     QCoreApplication app(argc, argv);
    50  
    51     Newspaper newspaper("Newspaper A");
    52     Reader reader;
    53     QObject::connect(&newspaper, &Newspaper::newPaper,
    54                      &reader,    &Reader::receiveNewspaper);
    55     newspaper.send();
    56  
    57     return app.exec();
    58 }

要使用槽函数功能，自定义的类必须要继承QObject类，并在第一行代码上写上Q\_OBJECT（无论是否使用信号槽，凡是QObject的子类都应该写上）。

Newspaper类有个signals代码块，它里面的就是该类的信号。信号是一个个函数名，返回值是void，不需要添加任何实现。

send()函数，只有一个语句emit newPaper(m\_name); 。emit意思是发出信号，此处为发出newPaper信号，参数为m\_name。

在main函数中，使用QObject::connect()来连接信号和槽。

原文：

https://www.devbean.net/2012/08/qt-study-road-2-signal-slot/

https://www.devbean.net/2012/08/qt-study-road-2-custom-signal-slot/

转载于:https://www.cnblogs.com/fategrandorder/p/9095231.html