Qt开发实现跨窗口信号槽通信

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QLabel>
#include <QString>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void receiveMsg(QString str);

private:
    QLabel *label;
};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "subwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    setWindowTitle("MainWindow");
    setFixedSize(400, 300);

    // add text label
    label = new QLabel(this);
    label->setText("to be changed");

    // open sub window and connect
    SubWindow *subwindow = new SubWindow(this);
    connect(subwindow, SIGNAL(sendText(QString)), this, SLOT(receiveMsg(QString)));
    subwindow->show(); // use open or exec both ok
}

void MainWindow::receiveMsg(QString str)
{
    // receive msg in the slot
    label->setText(str);
}

MainWindow::~MainWindow()
{
}

#ifndef SUBWINDOW_H
#define SUBWINDOW_H

#include <QDialog>

class SubWindow : public QDialog
{
    Q_OBJECT
public:
    explicit SubWindow(QWidget *parent = 0);

signals:
    void sendText(QString str);
public slots:
    void onBtnClick();
};

#endif // SUBWINDOW_H

#include "QPushButton"
#include "subwindow.h"

SubWindow::SubWindow(QWidget *parent) : QDialog(parent)
{
    setWindowTitle("SubWindow");
    setFixedSize(200, 100);

    QPushButton *button = new QPushButton("click", this);
    connect(button, SIGNAL(clicked()), this, SLOT(onBtnClick()));
}

void SubWindow::onBtnClick()
{
    // send signal
    emit sendText("hello qt");
}