有没有办法计算 QStandardItem 的高度？

Question

我创建了一个从 QListView 扩展的可扩展 ListView，当我只想显示标题数据（未扩展的项目）时一切正常，因为我给它一个硬编码的高度，即 64，出现细节展开项目时。但问题是我不知道细节的确切高度，因为细节可以一行或多行，我想根据项目内容适合项目高度。

这里是当项目展开或折叠时处理点击监听的代码：

LogListItemDelegate *delegate = static_cast<LogListItemDelegate *>(itemDelegate());
QStandardItem *item = static_cast<QStandardItemModel *>(model())->itemFromIndex(index);
bool expand = delegate->isExpandable() && mapFromGlobal(QCursor::pos()).x() >= visualRect(index).width() - 48;
bool expanded = index.data(LogListItemDelegate::DT_Expanded).toBool();

// here the height returned is header height, no containing the details which it is in expanding mode
int height = item->sizeHint().height();

        if (!expanded) {
            item->setData(true, LogListItemDelegate::DT_Expanded);
            item->setSizeHint(QSize(0, 150)); // 150 here must be dynamically calculated
        } else {
            item->setData(false, LogListItemDelegate::DT_Expanded);
            item->setSizeHint(QSize(0, 64)); // 64 is the header height, no prolem
        }

现在的问题是：item展开时如何计算高度？

结果：

编辑：

It is when I want to add the message to the list
void LogListView::addMessage(const QJsonObject &msg, const bool append)
{
    static int id = 1; // unique id for log items
    auto *item = new QStandardItem();
    item->setEditable(false);
    item->setData(QString("%1").arg(id++, 5, 10, QChar('0')), LogListItemDelegate::DT_Id);
    item->setData(msg["icon"], LogListItemDelegate::DT_ICON);
    item->setData(QDateTime::currentDateTime().toString("yyyy-MM-dd HH:mm:ss"), LogListItemDelegate::DT_Timestamp);
    item->setData(msg["title"], LogListItemDelegate::DT_Title);
    item->setData(msg["subtitle"], LogListItemDelegate::DT_Subtitle);
    item->setData(msg["details"], LogListItemDelegate::DT_Details);
    item->setData(false, LogListItemDelegate::DT_Expanded);
    // here I am unable to calculate the height, because the details does not have a specific height to set here, 
    // so when append the item to the list it is unvisible. If set the height 64, it is the exact height of the item without details, which is good
    //item->setSizeHint(QSize(0, 64));

    static_cast<QStandardItemModel *>(model())->appendRow(item);
    scrollToBottom();
}

就是sizeHint()中的代码

QSize LogListItemDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    bool expanded = index.data(DT_Expanded).toBool();
    QFont fntDetials = option.font;
    fntDetials.setPointSize(12);
    QRect r = option.rect;
    QFontMetrics fm(fntDetials);
    QString details = index.data(DT_Details).toString();
    QRect br = fm.boundingRect(r, Qt::TextWordWrap, details);
    return QSize(option.rect.width(), br.height()+64);
}

可惜不行……，我觉得Qt可以看看Android ListView及其回收功能来解决ListView的问题，这样一来，我觉得是非常非常痛苦的。

Answer 1

如果要设置自定义尺寸，应该使用QStyledItemDelegate的sizeHint方法，例如：

#include <QApplication>
#include <QStyledItemDelegate>
#include <QListView>
#include <QStandardItemModel>

class HeightDelegate: public QStyledItemDelegate
{
public:
    using QStyledItemDelegate::QStyledItemDelegate;
    QSize sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const override{
        QSize s = QStyledItemDelegate::sizeHint(option, index);
        // some calculation
        int h = (index.row()+1)*20;
        s.setHeight(h);
        return s;
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QListView w;
    QStandardItemModel model;
    HeightDelegate delegate;
    w.setItemDelegate(&delegate);
    w.setModel(&model);
    for(int i=0; i<8; i++){
        QStandardItem *it = new QStandardItem(QString::number(i));
        it->setBackground(QBrush(QColor(qrand()%255, qrand()%255, qrand()%255)));
        model.appendRow(it);
    }
    w.show();
    return a.exec();
}