如何修复自定义QItemDelegate中drawCheck的复选框渲染异常？

我给QTableView的第一列添加了自定义代理BooleanItemDelegate，当前遇到复选框渲染异常：当所有可见复选框均勾选时渲染正常，但当两个及以上复选框未勾选时，复选框的白色勾选标记会闪烁，仿佛仅被部分重绘而非完整绘制。相关代码如下：

头文件 BooleanItemDelegate.h #

#ifndef BOOLEANITEMDELEGATE_H
#define BOOLEANITEMDELEGATE_H

#include <QItemDelegate>
#include <QSqlTableModel>

class BooleanItemDelegate : public QItemDelegate
{

public:
    BooleanItemDelegate(QSqlTableModel* model, QObject* parent);
    ~BooleanItemDelegate();

public:
    void paint(QPainter* painter, const QStyleOptionViewItem &option, const QModelIndex& index) const;
    bool editorEvent(QEvent* event, QAbstractItemModel* model, const QStyleOptionViewItem& option, const QModelIndex& index);
};

#endif // BOOLEANITEMDELEGATE_H

源文件 BooleanItemDelegate.cpp #

#include "BooleanItemDelegate.h"
#include <qcoreevent.h>

BooleanItemDelegate::BooleanItemDelegate(QSqlTableModel* model, QObject* parent)
    : QItemDelegate(parent)
{}


BooleanItemDelegate::~BooleanItemDelegate()
{}

void BooleanItemDelegate::paint(
    QPainter* painter,
    const QStyleOptionViewItem& option,
    const QModelIndex& index
) const
{
    drawBackground(painter, option, index);
    drawCheck(painter, option, option.rect, index.data().toBool() ? Qt::Checked : Qt::Unchecked);
    drawFocus(painter, option, option.rect);
}


bool BooleanItemDelegate::editorEvent(QEvent* event, QAbstractItemModel* model, const QStyleOptionViewItem& option, const QModelIndex& index)
{
    if (event->type() == QEvent::MouseButtonRelease || event->type() == QEvent::MouseButtonDblClick )
    {
        model->setData(index, !model->data(index).toBool());
        event->accept();
    }
    return QItemDelegate::editorEvent(event, model, option, index);
}

解决思路 #

• 修复复选框绘制区域：当前直接把整个item的option.rect传给drawCheck，导致复选框占满整个单元格，重绘时容易出现区域重叠引发闪烁。应该通过样式获取复选框的正确绘制区域：

  void BooleanItemDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
  {
      painter->save();
      // 先绘制背景
      drawBackground(painter, option, index);
      // 获取复选框的正确位置
      QStyleOptionButton checkOpt;
      checkOpt.rect = style()->subElementRect(QStyle::SE_CheckBoxIndicator, &option, nullptr);
      checkOpt.state = option.state | (index.data().toBool() ? QStyle::State_On : QStyle::State_Off);
      // 绘制复选框
      style()->drawControl(QStyle::CE_CheckBox, &checkOpt, painter);
      // 绘制焦点框
      drawFocus(painter, option, option.rect);
      painter->restore();
  }
  

• 避免重复事件处理：在editorEvent中，处理完鼠标事件后仍调用父类的editorEvent，会导致同一事件被重复处理，触发多次数据变更和重绘，进而引发闪烁。处理完自定义逻辑后直接返回true即可：

  bool BooleanItemDelegate::editorEvent(QEvent* event, QAbstractItemModel* model, const QStyleOptionViewItem& option, const QModelIndex& index)
  {
      if (event->type() == QEvent::MouseButtonRelease || event->type() == QEvent::MouseButtonDblClick )
      {
          model->setData(index, !model->data(index).toBool());
          event->accept();
          return true; // 不再让父类处理该事件
      }
      return QItemDelegate::editorEvent(event, model, option, index);
  }
  

• 确保重绘区域精准：如果上述修改后仍有闪烁，可在调用setData时明确指定数据角色，确保模型正确触发dataChanged信号，让视图精准重绘目标单元格：

  model->setData(index, !model->data(index).toBool(), Qt::EditRole);
  

内容的提问来源于stack exchange，提问作者Joseph