qt - 在 QListView 的 QWidgetDelegate 的 paint() 方法中渲染 QWidget

Question

我在 QListView 中实现自定义小部件渲染时遇到了困难.
我目前有一个 QListView显示我的自定义模型 PlayQueue基于 QAbstractListModel .

这适用于简单的文本，但现在我想为每个元素显示一个自定义小部件。
所以我将 QStyledItemDelegate 子类化实现paint像这样的方法:

void QueueableDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index ) const
{
    if (option.state & QStyle::State_Selected)
        painter->fillRect(option.rect, option.palette.highlight());
    QWidget *widget = new QPushButton("bonjour");
    widget->render(painter);
}

选择背景已正确呈现，但未显示任何小部件。我试过简单的QPainter像 Qt 示例中的命令，这工作正常:

void QueueableDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index ) const
{
    if (option.state & QStyle::State_Selected)
        painter->fillRect(option.rect, option.palette.highlight());
    if (option.state & QStyle::State_Selected)
        painter->setPen(option.palette.highlightedText().color());
    painter->setFont(QFont("Arial", 10));
    painter->drawText(option.rect, Qt::AlignCenter, "Custom drawing");
}

所以我尝试了一些更改，例如:

更改 QStyledItemDelegate至QItemDelegate

添加 painter->save()和 painter->restore()围绕渲染

将小部件几何设置为可用大小

但是我现在有点卡住了，我在互联网上搜索了一段时间，但找不到任何我想要的示例，他们都在谈论编辑小部件(这更容易)或自定义绘制控件(预定义的，如进度条)。
但在这里我真的需要一个我创建的自定义小部件，其中包含一些布局、标签和像素图。
谢谢你的帮助!

我在 Ubuntu 11.04 上为 GCC 使用 Qt 4.7.3。

Answer 1

只是为了完成整个画面:进一步可以找到使用委托(delegate)将 QWidget 管理为 QListView 项的代码。

我终于找到了如何使用它的 paint(...) 方法使其在 QStyledItemDelegate 的子类中工作。

它似乎比以前的解决方案更有效地提高性能，但是这个声明需要通过调查 setIndexWidget() 对创建的 QWidget 的作用来验证 =)。

所以最后，这里是代码:

class PackageListItemWidget: public QWidget

......

class PackageListItemDelegate: public QStyledItemDelegate

......

void PackageListItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index ) const
{

// here we have active painter provided by caller

// by the way - we can't use painter->save() and painter->restore()
// methods cause we have to call painter->end() method before painting
// the QWidget, and painter->end() method deletes
// the saved parameters of painter

// we have to save paint device of the provided painter to restore the painter
// after drawing QWidget
QPaintDevice* original_pdev_ptr = painter->device();

// example of simple drawing (selection) before widget
if (option.state & QStyle::State_Selected)
    painter->fillRect(option.rect, option.palette.highlight());

// creating local QWidget (that's why i think it should be fasted, cause we 
// don't touch the heap and don't deal with a QWidget except painting)
PackageListItemWidget item_widget;

// Setting some parameters for widget for example
    // spec. params
item_widget.SetPackageName(index.data(Qt::DisplayRole).toString());     
    // geometry
item_widget.setGeometry(option.rect);

// here we have to finish the painting of provided painter, cause
//     1) QWidget::render(QPainter *,...) doesn't work with provided external painter 
//          and we have to use QWidget::render(QPaintDevice *,...)
//          which creates its own painter
//     2) two painters can't work with the same QPaintDevice at the same time
painter->end(); 

// rendering of QWidget itself
item_widget.render(painter->device(), QPoint(option.rect.x(), option.rect.y()), QRegion(0, 0, option.rect.width(), option.rect.height()), QWidget::RenderFlag::DrawChildren);   

// starting (in fact just continuing) painting with external painter, provided
// by caller
painter->begin(original_pdev_ptr);  

// example of simple painting after widget
painter->drawEllipse(0,0, 10,10);   
};