QSignalMapper Class

/**************************************************************************************
 *                       QT QSignalMapper
 *
 *     QSignalMapper可以看做是一个信号的转发类。将多个信号作为一个集合，当接受到信号之后，
 * 将信号转发出去，并且可以更改发送出去信号参数类型。进行映射之后，接受到信号将会发给
 * map()函数，而map()函数又会发送mapped()信号。
 *     Button是qt中常用到的控件，当使用多个Button时，如果每一个button都对应一个slot函数，
 * 就会显得很多余，使用QSignalMapper类就能避免这种情况，提高不少效率。
 * 参考：　　
 *        http://doc.qt.io/qt-4.8/qsignalmapper.html#setMapping
 *　　　http://blog.csdn.net/cuteqt/article/details/4306900
 * 
 *                                                        Tony Liu, 2016-5-20, Shenzhen
**************************************************************************************/
1. 首先分析参考链接中，QT官网的例子。
class ButtonWidget : public QWidget
{
    Q_OBJECT

public:
    ButtonWidget(QStringList texts, QWidget *parent = 0);

slots:
    void doclicked(const QString &text);

private:
    QSignalMapper *signalMapper;
};

ButtonWidget::ButtonWidget(QStringList texts, QWidget *parent)
    : QWidget(parent)
{
    signalMapper = new QSignalMapper(this);

    QGridLayout *gridLayout = new QGridLayout;
    for (int i = 0; i < texts.size(); ++i) {
        QPushButton *button = new QPushButton(texts[i]);

　　　　 //将信号发送给signalMapper对象的map()函数
        connect(button, SIGNAL(clicked()), signalMapper, SLOT(map()));

        //进行映射，表示当button发送信号给map()函数，map()函数将会发出mapped(texts[i])信号，将texts[i]作为参数
　　　　 signalMapper->setMapping(button, texts[i]);
        gridLayout->addWidget(button, i / 3, i % 3);
    }
　　 //发出的mapped()函数，由doclicked()函数接收
    connect(signalMapper, SIGNAL(mapped(const QString &)),
            this, SLOT(doclicked(const QString &)));

    setLayout(gridLayout);
}

2.自己实现
class MainWindow : public QMainWindow
{
    Q_OBJECT
    
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void buttonClicked(QWidget *w);


private:
    Ui::MainWindow *ui;

    QSignalMapper signalMapper;
};

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    signalMapper.setMapping(ui->pushButton_O_1, ui->pushButton_O_1);
    signalMapper.setMapping(ui->pushButton_O_2, ui->pushButton_O_2);
    signalMapper.setMapping(ui->pushButton_O_3, ui->pushButton_O_3);
    signalMapper.setMapping(ui->pushButton_O_4, ui->pushButton_O_4);
    signalMapper.setMapping(ui->pushButton_O_5, ui->pushButton_O_5);
    signalMapper.setMapping(ui->pushButton_O_6, ui->pushButton_O_6);
    signalMapper.setMapping(ui->pushButton_O_7, ui->pushButton_O_7);
    signalMapper.setMapping(ui->pushButton_O_8, ui->pushButton_O_8);
    signalMapper.setMapping(ui->pushButton_O_9, ui->pushButton_O_9);

    connect(ui->pushButton_O_1, SIGNAL(clicked()), &signalMapper, SLOT(map()));
    connect(ui->pushButton_O_2, SIGNAL(clicked()), &signalMapper, SLOT(map()));
    connect(ui->pushButton_O_3, SIGNAL(clicked()), &signalMapper, SLOT(map()));
    connect(ui->pushButton_O_4, SIGNAL(clicked()), &signalMapper, SLOT(map()));
    connect(ui->pushButton_O_5, SIGNAL(clicked()), &signalMapper, SLOT(map()));
    connect(ui->pushButton_O_6, SIGNAL(clicked()), &signalMapper, SLOT(map()));
    connect(ui->pushButton_O_7, SIGNAL(clicked()), &signalMapper, SLOT(map()));
    connect(ui->pushButton_O_8, SIGNAL(clicked()), &signalMapper, SLOT(map()));
    connect(ui->pushButton_O_9, SIGNAL(clicked()), &signalMapper, SLOT(map()));
    //发送的参数只能使QString和QWidget,QObject等，而QPushButton继承了QWidget
    connect(&signalMapper, SIGNAL(mapped(QWidget *)), this, SLOT(buttonClicked(QWidget *)));
    /* 给Button设置一个属性，并给属性添加值,如果一个按键带有多个参数的时候，
     * 设置属性是个不错的方法，可以设置多个属性
     */
    ui->pushButton_O_1->setProperty("gpio", 1);
    ui->pushButton_O_2->setProperty("gpio", 2);
    ui->pushButton_O_3->setProperty("gpio", 3);
    ui->pushButton_O_4->setProperty("gpio", 4);
    ui->pushButton_O_5->setProperty("gpio", 5);
    ui->pushButton_O_6->setProperty("gpio", 6);
    ui->pushButton_O_7->setProperty("gpio", 7);
    ui->pushButton_O_8->setProperty("gpio", 8);
    ui->pushButton_O_9->setProperty("gpio", 9);

}

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

void MainWindow::buttonClicked(QWidget *w)
{
    //获取属性,传入的参数使qvariant类型的，需要转化为int类型
    int gpioIndex = qvariant_cast<int>(w->property("gpio"));
    QString str = QString::number(gpioIndex, 10);
    //由于传入的参数使QWidget，如果要设置按键，需要转为QPushButton，才能操作button
    QString ioState = ((QPushButton *)w)->text();
}