c++ - 继承和 Qt 信号

Question

编辑:所以现在我必须让 QLCDNumber 可以点击。单击它需要重置 m_Count。我添加了一个继承自 QLCDNumber 的类 myLC​​DNumber。它所做的只是重新定义 mouseReleaseEvent(QMouseEvent *e) 以使用 ButtonCount 实例接收的自定义信号，这会将 m_Count 设置为 0。但它不起作用(再次)。看起来他找不到 clicked() 信号，尽管它是在 myLC​​DNumber 类中定义的。

myLCDNumber.h

#ifndef MYLCDNUMBER_H
#define MYLCDNUMBER_H

#include <iostream>
#include <QObject>
#include <QApplication>
#include <QPushButton>
#include <QLCDNumber>

class myLCDNumber : public QLCDNumber
{
    public:
        myLCDNumber(uint numDigits);
        ~myLCDNumber();
        void mouseReleaseEvent(QMouseEvent *e);

    signals:
        void clicked();
};

#endif // MYLCDNUMBER_H

myLCDNumber.cpp

#include <QMouseEvent>
#include "mylcdnumber.h"

myLCDNumber::myLCDNumber(uint numDigits):QLCDNumber(numDigits){}

myLCDNumber::~myLCDNumber(){}

void myLCDNumber::mouseReleaseEvent(QMouseEvent *e)
{
    qDebug("je suis bien dans le click");
    if (e->button() == Qt::LeftButton)
        emit clicked();
}

我应该创建一个基于 QPushButton 的 ButtonCount 类。它所做的只是计算它被使用的次数(通过类中的变量)。单击它会增加 m_Count 变量(通过 ButtonCount.Increment())，然后将 valueChanged 信号(以 m_Count 变量作为值)发送到 QLCDNumber 小部件上的 display() 槽

出于某种原因，单击按钮不会按预期增加 LCD 计数器。我认为每次单击按钮时都会正确修改 m_Count，但我无法验证它(无法进行调试)。

ButtonCount.h

#ifndef BUTTONCOUNT_H
#define BUTTONCOUNT_H

#include <iostream>
#include <QObject>
#include <QApplication>
#include <QPushButton>

class ButtonCount : public QPushButton
{
    Q_OBJECT

    public:
        ButtonCount(const QString & text, QWidget * parent = 0);
        ~ButtonCount();
        int m_Count;

    public slots:
        void Increment();

    signals:
        void valueChanged(int);
};

#endif // BUTTONCOUNT_H

ButtonCount.cpp

#include "buttoncount.h"
    ButtonCount::ButtonCount(const QString &text, QWidget *parent):QPushButton(text, parent)
    {
        m_Count = 0;
        QObject::connect(this,SIGNAL(clicked()),this,SLOT(Increment()));
    }

    ButtonCount::~ButtonCount(){}

    void ButtonCount::Increment(){
        m_Count++;
        emit valueChanged(m_Count);
    }

main.cpp

#include <QApplication>
#include <QWidget>
#include <QLabel>
#include <QLCDNumber>
#include <QLayout>
#include <QDial>
#include "buttoncount.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget window;

    ButtonCount *button_c = new ButtonCount("Count clicks");
    myLCDNumber *lcd = new myLCDNumber(2);
    lcd->setSegmentStyle(QLCDNumber::Filled);
    QObject::connect(button_c,SIGNAL(valueChanged(int)),lcd,SLOT(display(int)));
    QObject::connect(lcd,SIGNAL(clicked()),button_c,SLOT(reset()));
    QVBoxLayout *layout = new QVBoxLayout();

    layout->addWidget(lcd);
    layout->addWidget(button_c);

    window.setLayout(layout);

    window.show();

    return a.exec();
}

Answer 1

为什么要继承？这是糟糕的设计。新类型的简单对象可以很好地完成这项工作:

class ButtonCounter : public QObject {
    Q_OBJECT

    int mCounter;
public:
    Q_PROPERTY(int counter
               READ counter 
               WRITE setCounter
               NOTIFY counterChanged )

    explicit ButtonCounter(QObject *parent) : 
         QObject(parent),
         mCounter(0) {
    }

    explicit ButtonCounter(QAbstractButton *parent) : 
         QObject(parent),
         mCounter(0) {
        connect(parent, SIGNAL(clicked()), this, SLOT(countOne()));
    }
    int counter() const {
        return mCounter;
    }

public slots:
    void setCounter(int value) {
       if (mCounter != value) {
           mCounter = value;
           emmit counterChanged(mCounter);
       }
    }

    void countOne() {
       setCounter(mCounter+1);
    }

public signals:
    void counterChanged(int newValue);
};