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QT/自定义槽和信号

news 来源：原创 2024/5/15 22:53:08

创建两个类student和teacher，父类都为QObject

在teacher中自定义Signal，hungry

//自定义信号，写道signals下
signals://返回值void//只需要声明//可以有参数，可以重载void hungry();void hungry(QString FoodName);

在student中自定义Slot，treat

//自定义槽函数，写到public slots Qt5.0版本以上可以写成全局函数或者public作用域下或者lambda表达式
public slots://返回值void//需要声明和实现//可以有参数，可以重载void treat();void treat(QString FoodName);

当teacher对象发出hungry信号，调用treat槽函数

connect(tc, &teacher::hungry, st, &student::treat);

当遇到重载的槽函数时，需用函数指针指向对应的函数

    //连接信号槽//连接有参数信号和槽//当信号和槽发生重载的时候，函数指针可以指向函数地址，用函数指针明确对应的函数void(teacher::*teacherSignal)(QString) = &teacher::hungry;void(student::*studentSlot)(QString) = &student::treat;void(student::*studentSlotEmpty)() = &student::treat;connect(tc, teacherSignal, st, studentSlot);connect(btn1, &QPushButton::clicked, st, studentSlotEmpty);

Qstring转换为char类型的方法

//QString转char* 通过.toUtf8转为QByteArrary类型通过.data()转为char*
qDebug() << "请老师吃" << FoodName.toUtf8().data();

student.h

#ifndef STUDENT_H
#define STUDENT_H#include <QObject>
#include <QDebug>class student : public QObject
{Q_OBJECT
public:explicit student(QObject *parent = nullptr);signals://自定义槽函数，写到public slots Qt5.0版本以上可以写成全局函数或者public作用域下或者lambda表达式
public slots://返回值void//需要声明和实现//可以有参数，可以重载void treat();void treat(QString FoodName);void treat(QString FoodName, QString SecondFoodName);
};#endif // STUDENT_H

teacher.h

#ifndef TEACHER_H
#define TEACHER_H#include <QObject>
#include <QString>class teacher : public QObject
{Q_OBJECT
public:explicit teacher(QObject *parent = nullptr);//自定义信号，写道signals下
signals://返回值void//只需要声明//可以有参数，可以重载void hungry();void hungry(QString FoodName);
};#endif // TEACHER_H

widget.h

#ifndef WIDGET_H
#define WIDGET_H#include <QWidget>
#include <QPushButton>
#include <QTextEdit>
#include "mypushbutton.h"
#include "teacher.h"
#include "student.h"QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACEclass Widget : public QWidget
{Q_OBJECTpublic:Widget(QWidget *parent = nullptr);~Widget();teacher* tc;student* st;QPushButton* btn1;QPushButton* btn2;QPushButton* btn3;QPushButton* btn4;void display(QTextEdit *text1);void classIsOver();
private:Ui::Widget *ui;
};
#endif // WIDGET_H

widget.cpp

#include "widget.h"
#include "ui_widget.h"Widget::Widget(QWidget *parent): QWidget(parent), ui(new Ui::Widget)
{ui->setupUi(this);//new时括号内加入this，会将对象放入对象树，会自动调用析构函数this->tc = new teacher(this);this->st = new student(this);this->btn1 = new QPushButton;this->btn2 = new QPushButton;this->btn3 = new QPushButton("close", this);this->btn4 = new QPushButton("吃两个菜", this);btn1->setParent(this);btn1->setText("下课");btn2->setParent(this);btn2->setText("display");btn2->move(0,200);btn3->move(0,300);btn4->move(0,250);//连接信号槽//连接有参数信号和槽//当信号和槽发生重载的时候，函数指针可以指向函数地址，用函数指针明确对应的函数void(teacher::*teacherSignal)(QString) = &teacher::hungry;void(student::*studentSlot)(QString) = &student::treat;connect(tc, teacherSignal, st, studentSlot);//信号可以连接信号void(teacher::*teacherSignalEmpty)() = &teacher::hungry;void(student::*studentSlotEmpty)() = &student::treat;connect(tc, teacherSignalEmpty, st, studentSlotEmpty);connect(btn1, &QPushButton::clicked, tc, teacherSignalEmpty);//信号可以断开连接//disconnect(btn1, &QPushButton::clicked, tc, teacherSignalEmpty);//一个信号可以绑定多个槽函数//多个信号可以绑定同一个槽函数connect(btn2, &QPushButton::clicked, tc, teacherSignalEmpty);//槽函数的参数和信号的参数类型必须一一对应//信号的参数个数可以多余槽函数的参数个数，反之不可以//链接槽函数 注:信号的参数要大于等于槽函数的参数,//点击事件无参,但是槽函数需要传递ui参数//故槽函数采用Qt5之后支持的lambda表达式进行传参,常用=传递值,而不是&，因为当槽和信号连接时，当前控件会进入锁的状态，而=传递是创造新的值覆盖，不会过多影响效率，加上mutable关键字，可以修改按值传递的拷贝//新建一个texteditQTextEdit *text1 = new QTextEdit(this);//设置大小为200*100并放置在(300,100)处text1->resize(200, 100);text1->move(300, 100);//重置窗体大小为600*400this->resize(600, 400);connect(btn2, &QPushButton::clicked, text1, [=](){display(text1);});//Qt4版本信号和槽信号写法（不推荐）//利用Qt4版本连接有参信号和槽//优势参数直观//劣势参数类型不做匹配检测//connect(tc, SIGNAL(hungry(QString), st, SLOT(treat(QString)));//点击按钮，关闭窗口connect(btn3, &QPushButton::clicked, this, [=](){this->close();});connect(btn4, &QPushButton::clicked, this, [=](){this->st->treat("宫保鸡丁", "鱼香肉丝");});classIsOver();
}void Widget::display(QTextEdit *text1)
{text1->setText("I Love you more than I can say!");text1->append("我爱你在心口难开");
}void Widget::classIsOver()
{//触发自定义信号,emit是Qt关键字,使用：在A中对B发出信号emit this->tc->hungry("宫保鸡丁");
}Widget::~Widget()
{delete ui;
}