Qt信号与槽第三章

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mainwindow.h

#ifndef MAINWINDOW_H#define MAINWINDOW_H#include "signalandslot.h"#include <QMainWindow>namespace Ui {class MainWindow;}class MainWindow : public QMainWindow{    Q_OBJECTpublic:    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_OBJECTpublic:    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);

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