在QTableView中某列中添加Button的导致滚动条滚动的时候消失的问题

之前在项目上需要在表格中加入Button是按照以下两个文章的做法：

http://www.cnblogs.com/li-peng/p/3961843.html

http://www.cnblogs.com/li-peng/p/4029885.html

文章的做法是传统通过子类化QItemDelegate类来做的，通过paint函数在某列中画出QPushButton的Style。

但是这么做有一个问题，就是按钮画出来以后，但是拖动QTableView的滚动条的时候，会导致按钮所在的列的部分按钮又消失的问题。

没查到原因，但是最终还是在找到解决方案了。还是子类化QItemDelegate类，但是与之前的两个文章之前的做法有些不同，以下是正确的

代码：

Delegate头文件：

#pragma once

#include <QStyledItemDelegate>
#include <QString>
#include <QPersistentModelIndex>

class QStyleOptionButton;
class CTableWidget;
class QPushButton;

class AppRepoButtonDelegate : public QStyledItemDelegate
{
    Q_OBJECT

public:

    explicit AppRepoButtonDelegate(QObject *parent = Q_NULLPTR);
    ~AppRepoButtonDelegate();
public:
    void setText(const QString& text);
    void setStyleSheet(const QString& qss);

signals:
    void buttonClicked(const QModelIndex& index);
public:

    QWidget* createEditor(QWidget *parent,
        const QStyleOptionViewItem &option,
        const QModelIndex &index) const override;
   void paint(QPainter *painter, const QStyleOptionViewItem &option, 
        const QModelIndex &index) const override;
    void updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const override;
private slots:
    void cellEntered(const QModelIndex& index);
    void slotBtnClicked();
private:
    CTableWidget * m_table_view;
    bool isOneCellInEditMode;
    QPushButton* m_btn;
    QPersistentModelIndex m_currentEditedCellIndex;
    QString m_btnText;
    QString m_btnQss;
};

Delegate类的CPP实现文件：

#include "AppRepoButtonDelegate.h"

#include <QStyleOptionButton>
#include <QPainter>
#include <QApplication>
#include <QMouseEvent>
#include <QStandardItemModel>
#include <QPushButton>
#include <QTableView>

#include "CTableWidget.h"

AppRepoButtonDelegate::AppRepoButtonDelegate(QObject *parent)
    : QStyledItemDelegate(parent)
{
    CTableWidget *tabView = qobject_cast<CTableWidget*>(parent);
    if (tabView)
    {
        m_table_view = tabView;
        m_btn = new QPushButton(QStringLiteral(""), m_table_view);
        m_btn->hide();
        m_table_view->setMouseTracking(true);
        connect(m_table_view, SIGNAL(entered(QModelIndex)),
            this, SLOT(cellEntered(QModelIndex)));
        isOneCellInEditMode = false;
    }
}

AppRepoButtonDelegate::~AppRepoButtonDelegate()
{
}

void AppRepoButtonDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    int x, y, width, height;
    x = option.rect.left() + option.rect.width() / 2 - 20;
    y = option.rect.top() + 5;
    width = 60;
    height = 20;
    
    m_btn->setGeometry(QRect(x,y,width,height));
    m_btn->setText(m_btnText);
    m_btn->setStyleSheet(m_btnQss);
    if (option.state == QStyle::State_Selected)
        painter->fillRect(option.rect, option.palette.highlight());
    QPixmap map = QPixmap::grabWidget(m_btn);
    painter->drawPixmap(x, y, map);
}

QWidget* AppRepoButtonDelegate::createEditor(QWidget *parent, 
    const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    QPushButton * btn = new QPushButton(parent);
    connect(btn, &QPushButton::clicked, this, &AppRepoButtonDelegate::slotBtnClicked);
    btn->setText(m_btnText);
    btn->setStyleSheet(m_btnQss);
    return btn;
}

void AppRepoButtonDelegate::cellEntered(const QModelIndex& index)
{
    if (index.column() == 6 || index.column() == 7)
    {
        if (isOneCellInEditMode)
        {
            m_table_view->closePersistentEditor(m_currentEditedCellIndex);
        }
        m_table_view->openPersistentEditor(index);
        isOneCellInEditMode = true;
        m_currentEditedCellIndex = index;
    }
    else {
        if (isOneCellInEditMode)
        {
            isOneCellInEditMode = false;
            m_table_view->closePersistentEditor(m_currentEditedCellIndex);
        }
    }
}

void AppRepoButtonDelegate::updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, 
    const QModelIndex &index) const
{
    int x, y, width, height;
    x = option.rect.left() + option.rect.width() / 2 - 20;
    y = option.rect.top() + 5;
    width = 60;
    height = 20;
    editor->setGeometry(QRect(x, y, width, height));
}

void AppRepoButtonDelegate::setText(const QString& text)
{
    m_btnText = text;
}

void AppRepoButtonDelegate::setStyleSheet(const QString& qss)
{
    m_btnQss = qss;
}

void AppRepoButtonDelegate::slotBtnClicked()
{
    emit buttonClicked(m_currentEditedCellIndex);
}

用法：

 auto delegateBtn = new AppRepoButtonDelegate(ui->appTable);
        delegateBtn->setText(QStringLiteral("下载更新"));
        m_downloadUpdateDelegate = delegateBtn;
        connect(m_downloadUpdateDelegate, &AppRepoButtonDelegate::buttonClicked,
            this, &AppRepoPage::slotDownloadUpdateBtnClicked);
        ui->appTable->setItemDelegateForColumn(
            6, m_downloadUpdateDelegate); //给第6列添加下载更新按钮的委托

references:

https://stackoverflow.com/questions/12360111/qpushbutton-in-qtableview
https://stackoverflow.com/questions/25337740/how-to-add-qpushbutton-in-qtableview-when-loading-database-by-c
http://www.qtcentre.org/threads/32394-Add-QPushButton-to-cell-in-QTableView
https://forum.qt.io/topic/53467/how-to-add-qpushbutton-in-qtableview

https://stackoverflow.com/questions/43082419/create-pushbuttons-in-qtableview-with-qstyleditemdelegate-subclass/43109044#43109044 

https://qtadventures.wordpress.com/2012/02/04/adding-button-to-qviewtable/