Qt不同类之间信号槽连接

1.类必须继承QObject.

#ifndef TESTA_H
#define TESTA_H

#include <QObject>

class TestA : public QObject
{
    Q_OBJECT
public:
    );

    void runTestA();
signals:
    showMsg(QString str);
public slots:
};

#endif // TESTA_H

#include "testa.h"
#include<QDebug>
TestA::TestA(QObject *parent) : QObject(parent)
{

}

void TestA::runTestA()
{

    qDebug()<<"+++runtesta++";
    emit showMsg("ssssss");
}

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "testa.h"
namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    );
    ~MainWindow();

    TestA *pTestA;

private slots:
    void on_pushButton_clicked();
    void onShowMsg(QString str);

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include<QDebug>
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    pTestA=new TestA(this);
    connect(pTestA,SIGNAL(showMsg(QString)),this,SLOT(onShowMsg(QString)));
}

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

void MainWindow::on_pushButton_clicked()
{
   pTestA->runTestA();
}

void MainWindow::onShowMsg(QString str)
{
    //防止中文乱码
    QTextCodec::setCodecForCStrings(QTextCodec::codecForName("utf8"));

    qDebug()<<"+++++onshowmsg+";
}