Question

修改： 所以现在我必须使QLCDNumber可点击。单击它需要重置m_Count。我添加了一个继承自QLCDNumber的类myLCDNumber。它所做的就是重新定义mouseReleaseEvent（QMouseEvent * e）以使用ButtonCount实例接收的自定义信号，该实例将m_Count设置为0。但它不起作用（再次）。虽然在myLCDNumber类中定义了clicked（）信号，但看起来他无法找到它。

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();
}

我应该根据QPushButton创建一个ButtonCount类。它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（）插槽

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，但我无法对其进行验证（无需调试）。

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);
    }

的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

为什么继承？这是糟糕的设计。新类型的简单对象很好地完成了这项工作：

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);
};

继承和Qt信号

1 个答案: