Qt信号与槽第三章

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include "signalandslot.h"

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
signalandslot a,b;
private slots:
void on_action_2_triggered();

private:
Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

signalandslot.h

#ifndef SIGNALANDSLOT_H
#define SIGNALANDSLOT_H

#include <QObject>

class signalandslot : public QObject
{
Q_OBJECT
public:
explicit signalandslot(QObject *parent = 0);
int Data;
signals:
void DataChanged(int Data);
public slots:
void SetData(int Data);
};

#endif // SIGNALANDSLOT_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "signalandslot.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
ui->statusBar->showMessage(tr("a.Data=%1 b.Data=%2").arg(a.Data).arg(b.Data));
//Qt5的写法
connect(&b,&signalandslot::DataChanged,&a,&signalandslot::SetData);
}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::on_action_2_triggered()
{
b.SetData(100);
ui->statusBar->showMessage(tr("a.Data=%1 b.Data=%2").arg(a.Data).arg(b.Data));

}

void MainWindow::on_pushButton_clicked()
{
ui->statusBar->showMessage(tr("b.Data=%1").arg(b.Data));
}

signalandslot.cpp

#include "signalandslot.h"

signalandslot::signalandslot(QObject *parent) : QObject(parent)
{
Data=0;
}
void signalandslot::SetData(int inputData){
if(Data!=inputData){
Data=inputData;
//emit抛出信号
emit DataChanged(Data);
}
}

注意 

emit DateChanged(Data)//抛出信号

信号的传参

Qt4 和Qt5 的自定义建立信号与槽的方式不同

Qt4

QObject::connect(&newspaper,SIGNAL(newPaper(QString)),
&reader,    SLOT(receiveNewspaper(QString)));

Qt5

QObject::connect(&newspaper,&Newspaper::newPaper,
&reader,    &Reader::receiveNewspaper);