qt4典型的信号槽的实现

#ifndef DIALOG_H
#define DIALOG_H

#include <QDialog>

namespace Ui {
class Dialog;
}

class Dialog : public QDialog
{
Q_OBJECT

public:
explicit Dialog(QWidget *parent = 0);
~Dialog();

private slots:                       //槽函数，右击发送按钮的“转到槽”
void on_send_clicked();

signals:
void StringChange(QString str);  //信号

private:
Ui::Dialog *ui;
};

#endif // DIALOG_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

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

private slots:                                 //槽函数
void showString(QString str);

private:
Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

#include "dialog.h"
#include "ui_dialog.h"

Dialog::Dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog)
{
ui->setupUi(this);
}

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

void Dialog::on_send_clicked()
{
QString str = ui->StringlineEdit->text();   //保存编辑框上的文本
emit StringChange(str);                     //发送信号
}

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "dialog.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
Dialog *dlg = new Dialog(this);
connect(dlg,SIGNAL(StringChange(QString)),this,SLOT(showString(QString)));    //将对话框上的信号与自己的槽函数进行关联
dlg->show();
}

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

void MainWindow::showString(QString str)
{
ui->stringLabel->setText(str);
}

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();

return a.exec();
}