c++ - 单击旁边的按钮时如何引用动态创建的标签[Qt]

Question

每次按下“添加客户端”按钮 - 一个减号按钮、客户端名称、一个客户端计数器和一个加号按钮被添加到 gridLayout 的水平线上。我想在按下加号/减号按钮时更新计数 (QLabel)。

这是我的代码:

#include "widget.h"
#include "ui_widget.h"
#include <QDebug>
#include <QGridLayout>
#include <QLabel>

int row = 0;

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

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

void Widget::on_pushButton_clicked()
{
    QPushButton* minus_button = new QPushButton();
    QPushButton* plus_button = new QPushButton();
    minus_button->setText("-");
    plus_button->setText("+");

    QLabel* client_name = new QLabel(ui->lineEdit->text(), this);
    QLabel* client_count = new QLabel("", this);

    ui->gridLayout->addWidget(minus_button, row, 1, Qt::AlignTop|Qt::AlignHCenter);
    ui->gridLayout->addWidget(client_name, row, 2, Qt::AlignTop|Qt::AlignHCenter);
    ui->gridLayout->addWidget(client_count, row, 3, Qt::AlignTop|Qt::AlignHCenter);
    ui->gridLayout->addWidget(plus_button, row++, 4, Qt::AlignTop|Qt::AlignHCenter);

    connect(minus_button, SIGNAL(clicked(bool)), this, SLOT(minusCount()));
    connect(plus_button, SIGNAL(clicked(bool)), this, SLOT(plusCount()));
}

void Widget::minusCount(){
    //Here I want to somehow reference the client_count label which is in the same row
}
void Widget::plusCount(){
    //Here I want to somehow reference the client_count label which is in the same row
}

编辑:在 Kevin 的评论之后，这里是任何可能需要它的人的工作代码。

#include "widget.h"
#include "ui_widget.h"
#include <QDebug>
#include <QGridLayout>
#include <QLabel>
#include <QSignalMapper>

QSignalMapper* m_minusMapper;
QSignalMapper* m_plusMapper;

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    m_minusMapper = new QSignalMapper(this);
    connect(m_minusMapper, SIGNAL(mapped(QWidget*)), this, SLOT(minusCount(QWidget*)));

    m_plusMapper = new QSignalMapper(this);
    connect(m_plusMapper, SIGNAL(mapped(QWidget*)), this, SLOT(plusCount(QWidget*)));
}

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

void Widget::on_pushButton_clicked()
{
    QPushButton* minus_button = new QPushButton();
    minus_button->setObjectName("minus" + QString::number(row));
    minus_button->setText("-");

    QPushButton* plus_button = new QPushButton();
    plus_button->setObjectName("plus" + QString::number(row));
    plus_button->setText("+");

    QLabel* client_name = new QLabel(ui->lineEdit->text(), this);
    QLabel* client_count = new QLabel("0", this);

    ui->gridLayout->addWidget(minus_button, row, 1, Qt::AlignVCenter|Qt::AlignHCenter);
    ui->gridLayout->addWidget(client_name, row, 2, Qt::AlignVCenter|Qt::AlignHCenter);
    ui->gridLayout->addWidget(client_count, row, 3, Qt::AlignVCenter|Qt::AlignHCenter);
    ui->gridLayout->addWidget(plus_button, row++, 4, Qt::AlignVCenter|Qt::AlignHCenter);

    connect(minus_button, SIGNAL(clicked()), m_minusMapper, SLOT(map()));
    connect(plus_button, SIGNAL(clicked()), m_plusMapper, SLOT(map()));

    m_minusMapper->setMapping(minus_button, client_count);
    m_plusMapper->setMapping(plus_button, client_count);
}

void Widget::minusCount(QWidget *widget)
{
    QLabel *client_count = qobject_cast<QLabel*>(widget);
    QString initCount = client_count->text();
    int newCount = initCount.toInt() - 1;
    client_count->setText(QString::number(newCount));
}

void Widget::plusCount(QWidget *widget)
{
    QLabel *client_count = qobject_cast<QLabel*>(widget);
    QString initCount = client_count->text();
    int newCount = initCount.toInt() + 1;
    client_count->setText(QString::number(newCount));
}

Answer 1

Kevin 的回答原则上没问题，但由于我们现在已经有了 2016 年，而且 MSVC2010、gcc 4.7 和 Clang 3.1(可能还有更早的版本)支持 lambdas/C++11，我想添加一个没有QSignalMapper:

static void minusCount(QLabel *label)
{
    QString initCount = label->text();
    int newCount = initCount.toInt() - 1;
    label->setText(QString::number(newCount));
}

static void plusCount(QLabel *label)
{
    QString initCount = label->text();
    int newCount = initCount.toInt() + 1;
    label->setText(QString::number(newCount));
}

void Widget::on_pushButton_clicked()
{
    // ... add the labels and buttons, then:
    connect(minus_button, &QPushButton::clicked,
            client_count, [client_count]() { minusCount(client_count); });
    connect(plus_button, &QPushButton::clicked,
            client_count, [client_count]() { plusCount(client_count); });
}

此处按钮点击应更改的 client_count 标签在 lambda 中被捕获，并直接传递给处理它的函数。

此时 minusCount 和 plusCount 也可以是静态函数，因为它们只对作为参数传递的标签进行操作，所以它们独立于任何 Widget 实例。