QT 分页控件

#ifndef PAGENAVIGATOR_H
#define PAGENAVIGATOR_H

#include <QWidget>
#include <QList>
#include <QLabel>

//class QLabel;
//class QEvent;
//
namespace Ui
{
    class PageNavigator;
}

class PageNavigator : public QWidget
{
    Q_OBJECT

public:
    explicit PageNavigator(int blockSize = 3, QWidget *parent = nullptr);
    ~PageNavigator();

    int getBlockSize() const;
    int getMaxPage() const;
    int getCurrentPage() const;

    // 其他组件只需要调用这两个函数即可
    void setMaxPage(int page);   // 当总页数改变时调用
    void setCurrentPage(int page, bool signalEmitted = false); // 修改当前页时调用
    int  calMaxPage(int count,int pageNum);

protected:
    virtual bool eventFilter(QObject *watched, QEvent *e);

signals:
    void currentPageChanged(int page);

private:
    Ui::PageNavigator *ui;
    int m_blockSize;
    int m_maxPage;
    int m_currentPage;
    QList<QLabel *> *m_pageLabels;

    void setBlockSize(int blockSize);
    void updatePageLabels();
    void initialize();
};

#endif // PAGENAVIGATOR_H
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#include "pagenavigator.h"
#include "ui_pagenavigator.h"
#include"QIntValidator"



PageNavigator::PageNavigator(int blockSize/* = 3*/, QWidget *parent/* = nullptr*/)
	: QWidget(parent)
	, ui(new Ui::PageNavigator)
{
    ui->setupUi(this);
    setBlockSize(blockSize);
    initialize();

	m_maxPage = 0;
    setMaxPage(1);
	QString qss = QString(".QLabel[page=\"true\"] { padding: 6px; }")
		+ QString(".QLabel[currentPage=\"true\"] { color: rgb(190, 0, 0);}")
		+ QString(".QLabel[page=\"true\"]:hover { color: white; border-radius: 4px; background-color: qlineargradient(spread:reflect, x1:0, y1:0, x2:0, y2:1, stop:0 rgba(53, 121, 238, 255), stop:1 rgba(0, 202, 237, 255));}");
	this->setStyleSheet(qss);
}

PageNavigator::~PageNavigator()
{
    delete ui;
    delete m_pageLabels;
}

bool PageNavigator::eventFilter(QObject *watched, QEvent *e)
{
    if (e->type() == QEvent::MouseButtonRelease)
	{
        int page = -1;
        if (watched == ui->previousPageLabel)
		{
			page = getCurrentPage() - 1;
		}

        if (watched == ui->nextPageLabel)
		{
			page = getCurrentPage() + 1;
		}

        for (int i = 0; i < m_pageLabels->count(); ++i)
		{
            if (watched == m_pageLabels->at(i))
			{
                page = m_pageLabels->at(i)->text().toInt();
                break;
            }
        }

        if (-1 != page)
		{
			if (!ui->pageLineEdit->text().isEmpty())
			{
				ui->pageLineEdit->clear();
			}
            setCurrentPage(page, true);
            return true;
        }
    }

    if (watched == ui->pageLineEdit && e->type() == QEvent::KeyRelease)
	{
        QKeyEvent *ke = static_cast<QKeyEvent *>(e);
        if (ke->key() == Qt::Key_Enter || ke->key() == Qt::Key_Return)
		{
            setCurrentPage(ui->pageLineEdit->text().toInt(), true);
            //setMaxPage(ui->pageLineEdit->text().toInt()); // 测试生成多个页码
            return true;
        }
    }

    return QWidget::eventFilter(watched, e);
}

int  PageNavigator::calMaxPage(int count,int pageNum){
    int page=0;
    if(count%pageNum==0){
        page=count/pageNum;
    }else{
        page=(count/pageNum)+1;
    }

    page = qMax(page, 1);

    if (m_maxPage != page)
    {
        m_maxPage = page;
        m_currentPage = 1;
        updatePageLabels();
    }

}
int PageNavigator::getBlockSize() const
{
    return m_blockSize;
}

int PageNavigator::getMaxPage() const
{
    return m_maxPage;
}

int PageNavigator::getCurrentPage() const
{
    return m_currentPage;
}

void PageNavigator::setMaxPage(int page)
{
    page = qMax(page, 1);

    if (m_maxPage != page)
	{
        m_maxPage = page;
        m_currentPage = 1;
        updatePageLabels();
    }
}

void PageNavigator::setCurrentPage(int page, bool signalEmitted/* = false*/)
{
    page = qMax(page, 1);
    page = qMin(page, m_maxPage);

    if (page != m_currentPage)
	{
        m_currentPage = page;
        updatePageLabels();

        if (signalEmitted)
		{
            emit currentPageChanged(page);
        }
    }
}

void PageNavigator::setBlockSize(int blockSize)
{
    // 为了便于计算, block size 必须是奇数, 且最小为3
    blockSize = qMax(blockSize, 3);
    if (blockSize % 2 == 0)
	{
        ++blockSize;
    }
    m_blockSize = blockSize;
}

QString pageToText(int page)
{
	return QString::number(page);
}

// 初始化页码的labels
// 分成三个部分, 左...中...右
void PageNavigator::initialize()
{
    ui->pageLineEdit->installEventFilter(this);
    ui->pageLineEdit->setValidator(new QIntValidator(1, 10000000, this));

    ui->nextPageLabel->setProperty("page", "true");
    ui->previousPageLabel->setProperty("page", "true");
    ui->nextPageLabel->installEventFilter(this);
    ui->previousPageLabel->installEventFilter(this);

	m_pageLabels = new QList<QLabel *>();

    QHBoxLayout *leftLayout = new QHBoxLayout();
    QHBoxLayout *centerLayout = new QHBoxLayout();
    QHBoxLayout *rightLayout = new QHBoxLayout();
    leftLayout->setContentsMargins(0, 0, 0, 0);
    leftLayout->setSpacing(0);
    centerLayout->setContentsMargins(0, 0, 0, 0);
    centerLayout->setSpacing(0);
    rightLayout->setContentsMargins(0, 0, 0, 0);
    rightLayout->setSpacing(0);

    for (int i = 0; i < m_blockSize * 3; ++i)
	{
		QLabel *label = new QLabel(pageToText(i + 1), this);
        label->setProperty("page", "true");
        label->installEventFilter(this);

		m_pageLabels->append(label);

        if (i < m_blockSize)
		{
            leftLayout->addWidget(label);
        }
		else if (i < m_blockSize * 2)
		{
            centerLayout->addWidget(label);
        }
		else
		{
            rightLayout->addWidget(label);
        }
    }

    ui->leftPagesWidget->setLayout(leftLayout);
    ui->centerPagesWidget->setLayout(centerLayout);
    ui->rightPagesWidget->setLayout(rightLayout);
}

void PageNavigator::updatePageLabels()
{
    ui->leftSeparateLabel->hide();
    ui->rightSeparateLabel->hide();

    if (m_maxPage <= m_blockSize * 3)
	{
        for (int i = 0; i < m_pageLabels->count(); i += 1)
		{
            QLabel *label = m_pageLabels->at(i);
            if (i < m_maxPage)
			{
				label->setText(pageToText(i + 1));
                label->show();
            }
			else
			{
                label->hide();
            }

            if (m_currentPage - 1 == i)
			{
                label->setProperty("currentPage", "true");
            }
			else
			{
                label->setProperty("currentPage", "false");
            }

            label->setStyleSheet("/**/");
        }
        return;
    }

    // 以下情况为maxPageNumber大于blockSize * 3, 所有的页码label都要显示
    // c 为 currentPage
    // n 为 block size
    // m 为 maxPage

    // 1. c ∈ [1, n + n/2 + 1]: 显示前 n * 2 个, 后 n 个: 只显示右边的分隔符
    // 2. c ∈ [m - n - n/2, m]: 显示前 n 个, 后 n * 2 个: 只显示左边的分隔符
    // 3. 显示[1, n], [c - n/2, c + n/2], [m - 2*n + 1, m]: 两个分隔符都显示

    int c = m_currentPage;
    int n = m_blockSize;
    int m = m_maxPage;
    int centerStartPage = 0;
    if (c >= 1 && c <= n + n / 2 + 1)
	{
        // 1. c ∈ [1, n + n/2 + 1]: 显示前 n * 2 个, 后 n 个: 只显示右边的分隔符
        centerStartPage = n + 1;
        ui->rightSeparateLabel->show();
    }
	else if (c >= m - n - n / 2 && c <= m)
	{
        // 2. c ∈ [m - n - n/2, m]: 显示前 n 个, 后 n * 2 个: 只显示左边的分隔符
        centerStartPage = m - n - n + 1;
        ui->leftSeparateLabel->show();
    }
	else
	{
        // 3. 显示[1, n], [c - n/2, c + n/2], [m - n + 1, m]: 两个分隔符都显示
        centerStartPage = c - n / 2;
        ui->rightSeparateLabel->show();
        ui->leftSeparateLabel->show();
    }

    for (int i = 0; i < n; ++i)
	{
		m_pageLabels->at(i)->setText(pageToText(i + 1));                     // 前面 n 个
		m_pageLabels->at(n + i)->setText(pageToText(centerStartPage + i));   // 中间 n 个
		m_pageLabels->at(3 * n - i - 1)->setText(pageToText(m - i));         // 后面 n 个
    }

    for (int i = 0; i < m_pageLabels->count(); ++i)
	{
        QLabel *label = m_pageLabels->at(i);
        int page = label->text().toInt();
        if (page == m_currentPage)
		{
            label->setProperty("currentPage", "true");
        }
		else
		{
            label->setProperty("currentPage", "false");
        }

        label->setStyleSheet("/**/");
        label->show();
    }
}
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