2-5内置信号连接自定义槽

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtWidgets>
class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
private:
    void onClick();
    void onCheck(int state);
private:
    QPushButton* clickBtn;
    QLabel* label;

    // QObject interface
protected:
    void timerEvent(QTimerEvent *event);
};
#endif // MAINWINDOW_H

#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    QWidget* widget = new QWidget(this);
    setCentralWidget(widget);
    clickBtn = new QPushButton("点击",widget);
    QCheckBox* cd = new QCheckBox("connect",widget);
    cd->setCheckState(Qt::Checked);
    label = new QLabel(QTime::currentTime().toString(),widget);

    QHBoxLayout* hbox = new QHBoxLayout(widget);
    hbox->addWidget(clickBtn);
    hbox->addWidget(cd);
    hbox->addWidget(label);

    startTimer(1000);
    connect(clickBtn,&QPushButton::clicked,this,&MainWindow::onClick);
    connect(cd,&QCheckBox::stateChanged,this,&MainWindow::onCheck);
}

MainWindow::~MainWindow()
{

}

void MainWindow::onClick()
{
    statusBar()->showMessage("按钮被点击");
}

void MainWindow::onCheck(int state)
{
    statusBar()->showMessage("");
    if(state)
        connect(clickBtn,&QPushButton::clicked,this,&MainWindow::onClick);
    else
        disconnect(clickBtn,&QPushButton::clicked,this,&MainWindow::onClick);
}

void MainWindow::timerEvent(QTimerEvent *event)
{
    label->setText(QTime::currentTime().toString());
}