QStyledItemDelegate 和 QItemDelegate 都是继承 QAbstractItemDelegate，官方文档上说这两个类基本一样， 唯一不同是 QStyledItemDelegate 可以被 Qss 影响。
接下来查看 QStyledItemDelegate 和 QItemDelegate 的 paint() 源码( Qt版本为: 6.0.3):
// QStyledItemDelegate 使用 QStyle 的 drawControl 方法绘制可受到参数 widget 的样式影响
void QStyledItemDelegate::paint(QPainter *painter,
const QStyleOptionViewItem &option, const QModelIndex &index) const
{
Q_ASSERT(index.isValid());
QStyleOptionViewItem opt = option;
initStyleOption(&opt, index);
const QWidget *widget = QStyledItemDelegatePrivate::widget(option);
QStyle *style = widget ? widget->style() : QApplication::style();
style->drawControl(QStyle::CE_ItemViewItem, &opt, painter, widget);
}// QItemDelegate 使用 QPainter 原生绘制图形, Qss无法影响到 QItemDelegate
void QItemDelegate::paint(QPainter *painter,
const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
Q_D(const QItemDelegate);
Q_ASSERT(index.isValid());
QStyleOptionViewItem opt = setOptions(index, option);
// prepare
painter->save();
if (d->clipPainting)
painter->setClipRect(opt.rect);
// get the data and the rectangles
QVariant value;
QPixmap pixmap;
QRect decorationRect;
value = index.data(Qt::DecorationRole);
if (value.isValid()) {
// ### we need the pixmap to call the virtual function
pixmap = decoration(opt, value);
if (value.userType() == QMetaType::QIcon) {
d->tmp.icon = qvariant_cast<QIcon>(value);
d->tmp.mode = d->iconMode(option.state);
d->tmp.state = d->iconState(option.state);
const QSize size = d->tmp.icon.actualSize(option.decorationSize,
d->tmp.mode, d->tmp.state);
decorationRect = QRect(QPoint(0, 0), size);
} else {
d->tmp.icon = QIcon();
decorationRect = QRect(QPoint(0, 0), pixmap.size());
}
} else {
d->tmp.icon = QIcon();
decorationRect = QRect();
}
QRect checkRect;
Qt::CheckState checkState = Qt::Unchecked;
value = index.data(Qt::CheckStateRole);
if (value.isValid()) {
checkState = static_cast<Qt::CheckState>(value.toInt());
checkRect = doCheck(opt, opt.rect, value);
}
QString text;
QRect displayRect;
value = index.data(Qt::DisplayRole);
if (value.isValid() && !value.isNull()) {
text = d->valueToText(value, opt);
displayRect = d->displayRect(index, opt, decorationRect, checkRect);
}
// do the layout
doLayout(opt, &checkRect, &decorationRect, &displayRect, false);
// draw the item
drawBackground(painter, opt, index);
drawCheck(painter, opt, checkRect, checkState);
drawDecoration(painter, opt, decorationRect, pixmap);
drawDisplay(painter, opt, displayRect, text);
drawFocus(painter, opt, displayRect);
// done
painter->restore();
}
void QItemDelegate::drawBackground(QPainter *painter,
const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
if (option.showDecorationSelected && (option.state & QStyle::State_Selected)) {
QPalette::ColorGroup cg = option.state & QStyle::State_Enabled
? QPalette::Normal : QPalette::Disabled;
if (cg == QPalette::Normal && !(option.state & QStyle::State_Active))
cg = QPalette::Inactive;
painter->fillRect(option.rect, option.palette.brush(cg, QPalette::Highlight));
} else {
QVariant value = index.data(Qt::BackgroundRole);
if (value.canConvert<QBrush>()) {
QPointF oldBO = painter->brushOrigin();
painter->setBrushOrigin(option.rect.topLeft());
painter->fillRect(option.rect, qvariant_cast<QBrush>(value));
painter->setBrushOrigin(oldBO);
}
}
}下面是使用 QItemDelegate 和 QStyledItemDelegate 时，用 Qss 渲染QTableView 出现的不同效果:
调用代码:
// 代码尝试对两个 TableView 的 item 进行 Qss样式渲染
QString sQss = "QTableView::item{ border-bottom:1px solid red; }"
"QTableView::item::selected{ color:red; background:#EFF4FF;}";
m_pModel = new CTableModel(this);
QStringList lstHeader = {"测试列"};
m_pModel->SetHeader(lstHeader);
QVector<CTableModel::TRowData> vtModelData;
for (int i = 0; i < 10; i++)
{
CTableModel::TRowData tData;
tData.sItem1 = QString("数据%1_%2").arg(i).arg(1);
vtModelData.push_back(tData);
}
m_pModel->SetContentData(vtModelData);
ui->tvItem->setModel(m_pModel);
ui->tvStyleItem->setModel(m_pModel);
m_pItemDelegate = new CTableDelegate(ui->tvItem);
ui->tvItem->setItemDelegateForColumn(0, m_pItemDelegate);
m_pStyleItemDelegate = new CStyledTableDelegate(ui->tvStyleItem);
ui->tvStyleItem->setItemDelegateForColumn(0, m_pStyleItemDelegate);
ui->tvItem->setStyleSheet(sQss);
ui->tvStyleItem->setStyleSheet(sQss);运行图如下， 左边的 QTableView 使用的是 QItemDelegate，Qss 样式没有效果；右边的 QTableView 使用的是 QStyledItemDelegate , 单元格有选中效果和红色下划线。
当你想在单元格显示一些特殊图形时, 只是使用 QStyledItemDelegate 提供API可能并不能满足需求, 此时需要重写 paint 函数, 当重写paint函数时, 我认为 QStyledItemDelegate 和 QItemDelegate 并没有区别。你可以像 QItemDelegate 的 paint 函数那样, 使用QPainter 原生绘制; 也可以像 QStyledItemDelegate 那样使用 QStyle 绘制，并且可以用 Qss 辅助渲染，十分方便炫酷!
当然在使用的过程中可能会遇到一些问题，请参考如下代码:
// 初始化代码
m_pwgtStyle = new QWidget();
m_pbtnStyle = new QPushButton();
QStringList qss;
qss.append(QString("QPushButton{background-color:green;border:1px solid black; border-radius:6px;color:black;font-size:15px;}"));
qss.append(QString("QPushButton:pressed{background-color:red;}"));
qss.append(QString("QPushButton:!enabled{border:1px solid gray;color:gray;}"));
m_pbtnStyle->setStyleSheet(qss.join(""));void CStyledTableDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
QRect oRect = option.rect;
QStyleOptionButton oStyleButton;
oStyleButton.text = "测试按钮";
QMargins oMargins(10, 5, 10, 5);
oStyleButton.rect = oRect.marginsRemoved(oMargins);
oStyleButton.state |= QStyle::State_Enabled;
QApplication::style()->drawControl(QStyle::CE_PushButton, &oStyleButton, painter, m_pbtnStyle);
// m_pwgtStyle->style()->drawControl(QStyle::CE_PushButton, &oStyleButton, painter, m_pbtnStyle);
// m_pbtnStyle->style()->drawControl(QStyle::CE_PushButton, &oStyleButton, painter, m_pbtnStyle);
}
运行结果:
void CStyledTableDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
QRect oRect = option.rect;
QStyleOptionButton oStyleButton;
oStyleButton.text = "测试按钮";
QMargins oMargins(10, 5, 10, 5);
oStyleButton.rect = oRect.marginsRemoved(oMargins);
oStyleButton.state |= QStyle::State_Enabled;
// QApplication::style()->drawControl(QStyle::CE_PushButton, &oStyleButton, painter, m_pbtnStyle);
// m_pwgtStyle 是QWidget类型
m_pwgtStyle->style()->drawControl(QStyle::CE_PushButton, &oStyleButton, painter, m_pbtnStyle);
// m_pbtnStyle->style()->drawControl(QStyle::CE_PushButton, &oStyleButton, painter, m_pbtnStyle);
}运行结果:
void CStyledTableDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
QRect oRect = option.rect;
QStyleOptionButton oStyleButton;
oStyleButton.text = "测试按钮";
QMargins oMargins(10, 5, 10, 5);
oStyleButton.rect = oRect.marginsRemoved(oMargins);
oStyleButton.state |= QStyle::State_Enabled;
// QApplication::style()->drawControl(QStyle::CE_PushButton, &oStyleButton, painter, m_pbtnStyle);
// m_pwgtStyle->style()->drawControl(QStyle::CE_PushButton, &oStyleButton, painter, m_pbtnStyle);
// m_pbtnStyle 是 QPushButton
m_pbtnStyle->style()->drawControl(QStyle::CE_PushButton, &oStyleButton, painter, m_pbtnStyle);
}运行结果:
可以看到只有 QPushButton 的 QStyle 对象在渲染控件的时候有 drawControl 的第四个参数的 Qss 效果。 这是为什么呢? 答案是在初始化的时候，代码只是对 m_pbtnStyle 这个对象设置了 Qss, 导致 m_pbtnStyle->style() 对象类型为 QStyleSheetStyle(这个类型在 Qt 库里不公开), 而其他对象的 style() 类型是 QWindowsVistaStyle(这个类型也不公开)。 由此可以推测只有类型是 QStyleSheetStyle 类型才能渲染出 Qss 效果，只要 m_pwgtStyle 也设置 Qss 就可以渲染出带有Qss效果的UI