第10课 初探 Qt 中的消息处理

bool connect(const QObject* sender,     //发送对象
             const char* signal,        //消息名
             const QObject* receiver,   //接收对象
             const char* method,        //接收者成员函数（消息处理函数）
             Qt::ConnectionType type = Qt::AutoConnection);

#include <QApplication>
#include <QPushButton>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QPushButton b; //顶级组件
    
    b.setText("Click me to quit!");
    b.show();

    //将按钮b的clicked消息映射到a的quit函数
    QObject::connect(&b, SIGNAL(clicked()), &a, SLOT(quit()));

    return a.exec();
}

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

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QCalculatorUI* cal = QCalculatorUI::NewInstance();
    int ret = -1;

    if(cal != NULL)
    {
        cal->show();
        ret = a.exec();

        delete cal;
    }

    return ret;
}

#ifndef _QCALCULATORUI_H_
#define _QCALCULATORUI_H_

#include <QWidget>
#include <QLineEdit>
#include <QPushButton>

class QCalculatorUI : public QWidget
{
    //要自定义信号和槽，必须在最开始的这里添加Q_OBJECT
    Q_OBJECT
private:
    QLineEdit* m_edit;
    QPushButton* m_buttons[20];

    //二阶构造法:当new一个QLineEdit和一些按钮时可能会失败，所以采用二阶构造
    QCalculatorUI(); //第1阶——先隐藏构造函数
    bool construct();//第2阶

private slots: //声明槽时得加slots
    void onButtonClicked();

public:
    static QCalculatorUI* NewInstance();
    void show();
    ~QCalculatorUI();
};

#endif  //_QCALCULATORUI_H_

#include "QCalculatorUI.h"
#include <QDebug>

QCalculatorUI::QCalculatorUI(): QWidget(NULL, Qt::WindowCloseButtonHint)
{

}

bool QCalculatorUI::construct()
{
    bool ret = true;

    const char* btnText[20] =
    {
        "7", "8", "9", "+", "(",
        "4", "5", "6", "-", ")",
        "1", "2", "3", "*", "←",
        "0", ".", "=", "/", "C",
    };

    m_edit = new QLineEdit(this);//le的生命期由父组件来管理
    if( m_edit != NULL)
    {
        m_edit->move(10, 10);
        m_edit->resize(240, 30);
        m_edit->setReadOnly(true); //设置编辑框的只读属性
    }
    else
    {
        ret = false;
        return ret;
    }

    for(int i = 0; (i < 4) && ret; i++)
    {
        for(int j = 0; (j< 5) && ret; j++)
        {

            m_buttons[i * 5 + j] = new QPushButton(this);//按钮的生命期由父组件来管理
            if (m_buttons[i * 5 + j] != NULL)
            {
                m_buttons[i * 5 + j]->resize(40, 40);
                m_buttons[i * 5 + j]->move(10 + j * 50, 50 + i * 50);
                m_buttons[i * 5 + j]->setText(btnText[i * 5 + j]);

                //消息映射
                //1.消息名（信号）要加SIGNAL关键字，消息处理函数（槽）：用SLOT关键字
                //2.信号和槽的函数签名必须一致，即都是无参的函数，返回值void
                connect(m_buttons[i*5+j], SIGNAL(clicked()), this, SLOT(onButtonClicked()));
            }
            else
            {
                ret = false;
            }
        }
    }

    return ret;
}

QCalculatorUI* QCalculatorUI::NewInstance()
{
    QCalculatorUI* ret = new QCalculatorUI();

    if((ret == NULL) || !ret->construct())
    {
        delete ret;//删除半成品
        ret = NULL;
    }

    return ret;
}

void  QCalculatorUI::show()
{
    QWidget::show();
    setFixedSize(width(), height());
}

void QCalculatorUI::onButtonClicked()
{
    //sender是QObject类的，用于表示消息的发送者
    QPushButton* btn = (QPushButton*)sender();

    qDebug() << "onButtonClicked()";
    qDebug() << btn->text();

}

 QCalculatorUI::~QCalculatorUI()
 {

 }