直播相关02-录制麦克风声音，QT 信号与槽，自定义信号和槽

一信号与槽函数

#include "mainwindow.h"
#include <QPushButton>
#include <iostream>
using namespace std;//我们的目的是在 window中加入一个button，当点击这个button后，关闭 MainWindow 。
MainWindow::MainWindow(QWidget *parent): QMainWindow(parent)
{//注意，这里是new 了一个 QpushButton的，那么理论上要 delete 这个loginButton 。这里为什么 没有呢？QPushButton * loginButton = new QPushButton();loginButton->setText("登陆");loginButton->setParent(this); // 将自己挂载到当前的 mianwindow上，这意味着，当 mainwindows 销毁的时候，loginbutton 会跟着销毁，因此不用手动的调用 elete loginbuttonloginButton->setFixedSize(100,30); // 设置button 为固定大小//我们将 loginbutton 的 clicked信号，给MainWindow 的 close槽函数。//qpushbutton 的clicked 信号，是qpushbutton 自带的信号//mainwindows 的close 槽函数，是 mainwindows 自带的槽函数connect(loginButton,&QPushButton::clicked,this,&MainWindow::close);}MainWindow::~MainWindow()
{
}

二自定义信号和自定义槽函数

1.自定义信号，添加一个C++ 类，要继承 QObject

主要你要自定义信号与槽，就一定要 Add Q_OBJECT

sender.h 文件

#ifndef SENDER_H
#define SENDER_H#include <QObject>class Sender : public QObject
{//主要你要自定义信号与槽，就一定要 Add Q_OBJECT，这个取消了会有问题Q_OBJECT
public:explicit Sender(QObject *parent = nullptr);signals://自定义信号，只需要在.h文件中声明就可以了，不需要在.cpp中实现void exit();void start();
};#endif // SENDER_H

2.自定义槽函，添加一个C++类，要继承 QObject

在receiver.h 中定义这两个槽函数

在receiver.cpp中实现这两个槽函数

#ifndef RECEIVER_H
#define RECEIVER_H#include <QObject>class receiver : public QObject
{//主要你要自定义信号与槽，就一定要 Add Q_OBJECT，这个取消了会有问题Q_OBJECT
public:explicit receiver(QObject *parent = nullptr);signals://槽函数是要给别人调用的，因此在public slots 后 写 槽函数,在.cpp文件中写实现.
public slots:void handleExit();void handleStart();};#endif // RECEIVER_H

#include "receiver.h"
#include <iostream>
using namespace std;receiver::receiver(QObject *parent) : QObject(parent)
{}void receiver::handleExit(){cout<<"receiver handleExit method "<<endl;
}
void receiver::handleStart(){cout<<"receiver handleStart method "<<endl;
}

3.调用

这里为了方便期间，将上述两个类重命名为 customerreceiver.h 和 customersender.h

//将信号发送者和信号接受者建立关联
//使用emit 发送信号, 实际上就是调用发送者的信号函数

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "customersender.h"
#include "customerreceiver.h"
#include <iostream>
using namespace std;MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::MainWindow)
{cout<<"qt custom single custom slot"<<endl;ui->setupUi(this);CustomerSender * customersender = new CustomerSender;CustomerReceiver * customerrecevier =  new CustomerReceiver();//将信号发送者 和 信号 接受者 建立关联connect(customersender,&CustomerSender::start,customerrecevier,&CustomerReceiver::handleStart);connect(customersender,&CustomerSender::exit,customerrecevier,&CustomerReceiver::handleExit);cout<<"00000 log for watch"<<endl;//使用emit 发送信号, 实际上就是 调用 发送者的信号函数emit customersender->start();cout<<"11111log for watch"<<endl;emit customersender->exit();cout<<"222"<<endl;//由于 customersender 和 customerrecevier 并没有挂载到当前mainwindows上，类似这样customersender->setParent(this);因此要手动deletedelete customersender;delete customerrecevier;
}MainWindow::~MainWindow()
{delete ui;
}

4. 当自定义信号和自定义槽函数有参数或者返回值的时候

自定义信号 addmethodstart ，参数为 int a 和 int b

返回值double 目前不知道有啥用

signals://自定义信号，只需要在.h文件中声明就可以了，不需要在.cpp中实现void exit();void start();double addmethodstart(int a ,int b );

自定义槽函数

    int handleAddFuncation();double handleAddFuncation2(int n , int m);int CustomerReceiver::handleAddFuncation(){cout<<"CustomerReceiver handleAddFuncation method return 100"<<endl;return 100;
}double CustomerReceiver::handleAddFuncation2(int n , int m){cout<<"CustomerReceiver handleAddFuncation2 method return n+m "<< n+m << endl;return n+m;
}

当我们发送一个信号的时候，如果有槽函数有对应的 int，int 参数，则会接受信号发送的2000,3000的值传递到槽函数中。

如果槽函数没有对应的int，int 参数，则不传递

    connect(customersender,&CustomerSender::addmethodstart,customerrecevier,&CustomerReceiver::handleAddFuncation);cout<< emit customersender->addmethodstart(200,300);//由于 handleAddFuncation 函数没有参数，因此这个200,300传递不到槽函数handleAddFuncation中cout<<"333"<<endl;connect(customersender,&CustomerSender::addmethodstart,customerrecevier,&CustomerReceiver::handleAddFuncation2);cout<< emit customersender->addmethodstart(2000,3000);//由于handleAddFuncation2 有int，int 的参数 ，因此这个2000,3000会传递给槽函数 handleAddFuncation2

返回值问题，信号的返回值目前没有发现意义是啥，

槽函数的返回值可以通过 emit 信号函数返回。

例如：

cout<< emit customersender->addmethodstart(200,300);
会打印 100出来，这是因为 对应的槽函数 handleAddFuncation 返回值是100

5. 连接多个信号

connect 函数除了可以连接一个信号和一个槽函数外，

还可以连接一个信号和另一个信号 .

类似于连锁反应

customersender2.h

#ifndef CUSTOMERSENDER2_H
#define CUSTOMERSENDER2_H#include <QObject>class customersender2 : public QObject
{Q_OBJECT
public:explicit customersender2(QObject *parent = nullptr);signals:void deletebutton2();
};#endif // CUSTOMERSENDER2_H

customersender3.h

#ifndef CUSTOMERSENDER3_H
#define CUSTOMERSENDER3_H#include <QObject>class customersender3 : public QObject
{Q_OBJECT
public:explicit customersender3(QObject *parent = nullptr);signals:void deletebutton3();
};#endif // CUSTOMERSENDER3_H

customerreceuver2.h

#ifndef CUSTOMERRECEUVER2_H
#define CUSTOMERRECEUVER2_H#include <QObject>class customerreceuver2 : public QObject
{Q_OBJECT
public:explicit customerreceuver2(QObject *parent = nullptr);signals:public slots:void handledeletebutton2();
};#endif // CUSTOMERRECEUVER2_H

customerreceuver3.h

#ifndef CUSTOMERRECEUVER3_H
#define CUSTOMERRECEUVER3_H#include <QObject>class customerreceuver3 : public QObject
{Q_OBJECT
public:explicit customerreceuver3(QObject *parent = nullptr);signals:public slots:void handledeletebutton3();
};#endif // CUSTOMERRECEUVER3_H

customerreceuver2.cpp

#include "customerreceuver2.h"
#include <iostream>
using namespace  std;customerreceuver2::customerreceuver2(QObject *parent) : QObject(parent)
{}void customerreceuver2::handledeletebutton2(){cout<<"customerreceuver2::handledeletebutton2"<<endl;
}

customerreceuver3.cpp

#include "customerreceuver3.h"
#include <iostream>
using namespace std;customerreceuver3::customerreceuver3(QObject *parent) : QObject(parent)
{}void customerreceuver3::handledeletebutton3(){cout<<"customerreceuver3::handledeletebutton3"<<endl;}

调用

        cout<<" single to single"<<endl;customersender2 *cus2 = new customersender2;customersender3 *cus3 = new customersender3;customerreceuver2 *cusre2 =  new customerreceuver2;customerreceuver3 *cusre3 =  new customerreceuver3;connect(cus2, &customersender2::deletebutton2,cusre2,&customerreceuver2::handledeletebutton2);emit cus2->deletebutton2();cout<<"111"<<endl;connect(cus3, &customersender3::deletebutton3,cusre3,&customerreceuver3::handledeletebutton3);emit cus3->deletebutton3();cout<<"222 "<<endl;cout<<"after this line will be test single to single"<<endl;//让 sender2 的信号deletebutton2 唤醒 sender3 的信号 deletebutton3connect(cus2, &customersender2::deletebutton2,cus3, &customersender3::deletebutton3);emit cus2->deletebutton2();cout<<"333333"<<endl;//    single to single
//    customerreceuver2::handledeletebutton2
//    111
//    customerreceuver3::handledeletebutton3
//    222 
//    after this line will be test single to single
//    customerreceuver2::handledeletebutton2
//    customerreceuver3::handledeletebutton3
//    333333

6.labmda 表达式

    //for test labmda，假设我们不想写receiverconnect(cus2, &customersender2::deletebutton2,[](){cout<<"labmda called"<<endl;});emit cus2->deletebutton2();cout<<"666666"<<endl;