QT——信号槽-白红宇

QT——信号槽

阅读量：7099 次

发布时间：2019-06-28

本文共 3396 字，大约阅读时间需要 11 分钟。

结合教程，写出如下关于信号槽的代码，将教程中信号槽两种方式写入同一个界面中。

#include "mainwindow.h"#include 
     
      #include 
      
       #include 
       
        #include 
        
         int main(int argc, char *argv[]){    QApplication a(argc, argv);    //MainWindow w;    //w.show();    QWidget *myWidget = new QWidget;    myWidget->setWindowTitle("Hello World");    //信号槽    QPushButton *button0 = new QPushButton;    button0->setText("Quit");    QObject::connect(button0, &QPushButton::clicked, &QApplication::quit);     // Lambda表达式标准输出    QPushButton *button = new QPushButton;    button->setText("std::out");    QObject::connect(button, &QPushButton::clicked, [](bool) {        qDebug() << "You clicked me!";    });    QHBoxLayout *layout = new QHBoxLayout;    //layout->addItem(button0);    layout->addWidget(button0);    layout->addWidget(button);    myWidget->setLayout(layout);    myWidget->show();    return a.exec();}

Qt5中信号槽的定义：

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);

connect()一般会使用前面四个参数，第一个是发出信号的对象，第二个是发送对象发出的信号，第三个是接收信号的对象，第四个是接收对象在接收到信号之后所需要调用的函数。也就是说，当 sender 发出了 signal 信号之后，会自动调用 receiver 的 slot 函数。

connect(sender,   signal,   receiver,   slot);

自定义信号槽：

//newspaper.h#ifndef NEWSPAPER_H#define NEWSPAPER_H#include 
     
      //使用信号槽必须继承QBject类class Newspaper : public QObject{    //QBject类及其子类，都必须在第一行写Q_OBJECT    //该宏应放于头文件中    Q_OBJECTpublic:    Newspaper(const QString & name) :        m_name(name)    {    }    void send()    {        //emit 的含义是发出newPaper()的信号        emit newPaper(m_name);    }    //信号函数，返回值为void，参数是类要让外界获取的数据signals:    void newPaper(const QString &name);private:    QString m_name;};#endif // NEWSPAPER_H

//reader.h#ifndef READER_H#define READER_H#include 
     
      #include 
      
       class Reader : public QObject{    Q_OBJECTpublic:    Reader() {}    //槽函数    void receiveNewspaper(const QString & name)    {        qDebug() << "Receives Newspaper: " << name;    }};#endif // READER_H

#include "mainwindow.h"#include "newspaper.h"#include "reader.h"#include 
     
      #include 
      
       #include 
       
        #include 
        
         int main(int argc, char *argv[]){    QCoreApplication app(argc, argv);    //MainWindow w;    //w.show();    Newspaper newspaper("Newspaper A");    Reader reader;    //信号连接机制    QObject::connect(&newspaper, &Newspaper::newPaper,                     &reader,    &Reader::receiveNewspaper);    newspaper.send();    return app.exec();}

编译文件，报错——LNK2001，无法链接解析的外部符号。

解决方法：将Project的同级编辑文件删除，重新编译既可。

输出：

转载于:https://www.cnblogs.com/farewell-farewell/p/7159799.html

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