在QTableView中显示动画图标的最佳方法是什么？

Question

我一直在努力解决这个问题,我似乎无法找到正确的方法.

我想要的是能够使用动画图标作为我的一些项目的装饰(通常表明该特定项目正在进行一些处理).我有一个自定义表模型,我在一个显示QTableView.

我的第一个想法是创建一个自定义委托,负责显示动画.当传递a QMovie作为装饰角色时,代表将连接到QMovie每个新框架可用时更新显示(参见下面的代码).但是,在调用委托paint方法后,画家似乎仍然无效(调用画家save方法时出错,可能是因为指针不再指向有效内存).

另一种解决方案是dataChanged每当新帧可用时发出项目的信号,但1)会产生许多不必要的开销,因为数据没有真正改变; 2)在模型级别处理电影似乎并不干净:显示层(QTableView或代理人)应负责处理新帧的显示.

有没有人知道在Qt视图中显示动画的干净(并且最好是高效)方式？

---

对于那些感兴趣的人,这里是我开发的代表的代码(目前不起作用).

// Class that paints movie frames every time they change, using the painter
// and style options provided
class MoviePainter : public QObject
{
    Q_OBJECT

  public: // member functions
    MoviePainter( QMovie * movie, 
                  QPainter * painter, 
                  const QStyleOptionViewItem & option );

  public slots:
    void paint( ) const;

  private: // member variables
    QMovie               * movie_;
    QPainter             * painter_;
    QStyleOptionViewItem   option_;
};


MoviePainter::MoviePainter( QMovie * movie,
                            QPainter * painter,
                            const QStyleOptionViewItem & option )
  : movie_( movie ), painter_( painter ), option_( option )
{
    connect( movie, SIGNAL( frameChanged( int ) ),
             this,  SLOT( paint( ) ) );
}

void MoviePainter::paint( ) const
{
    const QPixmap & pixmap = movie_->currentPixmap();

    painter_->save();
    painter_->drawPixmap( option_.rect, pixmap );
    painter_->restore();
}

//-------------------------------------------------

//Custom delegate for handling animated decorations.
class MovieDelegate : public QStyledItemDelegate
{
    Q_OBJECT

  public: // member functions
    MovieDelegate( QObject * parent = 0 );
    ~MovieDelegate( );

    void paint( QPainter * painter, 
                const QStyleOptionViewItem & option, 
                const QModelIndex & index ) const;

  private: // member functions
    QMovie * qVariantToPointerToQMovie( const QVariant & variant ) const;

  private: // member variables
    mutable std::map< QModelIndex, detail::MoviePainter * > map_;
};

MovieDelegate::MovieDelegate( QObject * parent )
  : QStyledItemDelegate( parent )
{
}

MovieDelegate::~MovieDelegate( )
{
    typedef  std::map< QModelIndex, detail::MoviePainter * > mapType;

          mapType::iterator it = map_.begin();
    const mapType::iterator end = map_.end();

    for ( ; it != end ; ++it )
    {
        delete it->second;
    }
}

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

    const QVariant & data = index.data( Qt::DecorationRole );

    QMovie * movie = qVariantToPointerToQMovie( data );

    // Search index in map
    typedef std::map< QModelIndex, detail::MoviePainter * > mapType;

    mapType::iterator it = map_.find( index );

    // if the variant is not a movie
    if ( ! movie )
    {
        // remove index from the map (if needed)
        if ( it != map_.end() )
        {
            delete it->second;
            map_.erase( it );
        }

        return;
    }

    // create new painter for the given index (if needed)
    if ( it == map_.end() )
    {
        map_.insert( mapType::value_type( 
                index, new detail::MoviePainter( movie, painter, option ) ) );
    }
}

QMovie * MovieDelegate::qVariantToPointerToQMovie( const QVariant & variant ) const
{
    if ( ! variant.canConvert< QMovie * >() ) return NULL;

    return variant.value< QMovie * >();
}

Answer 1

最好的解决方案是在委托中使用QSvgRenderer。

它非常容易实现，与 gif 不同，SVG 是轻量级的并且支持透明度。

    TableViewDelegate::TableViewDelegate(TableView* view, QObject* parent)
    : QStyledItemDelegate(parent), m_view(view)
{
    svg_renderer = new QSvgRenderer(QString{ ":/res/img/spinning_icon.svg" }, m_view);

    connect(svg_renderer, &QSvgRenderer::repaintNeeded,
        [this] {
        m_view->viewport()->update();
    });
}


void TableViewDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option,
    const QModelIndex& index) const
{
    QStyleOptionViewItem opt{ option };
    initStyleOption(&opt, index);

    if (index.column() == 0) {
        if (condition)
        {
            // transform bounds, otherwise fills the whole cell
            auto bounds = opt.rect;
            bounds.setWidth(28);
            bounds.moveTo(opt.rect.center().x() - bounds.width() / 2,
                opt.rect.center().y() - bounds.height() / 2);

            svg_renderer->render(painter, bounds);
        }
    }

    QStyledItemDelegate::paint(painter, opt, index);
}

这是一个不错的网站，您可以在其中生成自己的旋转图标并以 SVG 格式导出。

Answer 2

为了记录,我最终QAbstractItemView::setIndexWidget在paint我的委托方法中使用,在项目内插入一个QLabel显示内容QMovie(见下面的代码).

此解决方案非常好用,并将显示问题与模型分开.一个缺点是标签中新框架的显示导致整个项目再次渲染,导致几乎连续调用委托paint方法......

为了减少这些调用所带来的开销,我尝试通过重用现有标签(如果有的话)来最小化在委托中处理电影所做的工作.但是,这会在调整窗口大小时导致奇怪的行为:动画向右移动,就像两个标签并排放置一样.

好吧,这是一个可能的解决方案,随时评论如何改进它!

// Declaration

#ifndef MOVIEDELEGATE_HPP
#define MOVIEDELEGATE_HPP

#include <QtCore/QModelIndex>
#include <QtGui/QStyledItemDelegate>


class QAbstractItemView;
class QMovie;


class MovieDelegate : public QStyledItemDelegate
{
    Q_OBJECT

  public: // member functions

    MovieDelegate( QAbstractItemView & view, QObject * parent = NULL );

    void paint( QPainter * painter, 
                const QStyleOptionViewItem & option, 
                const QModelIndex & index ) const;


  private: // member functions

    QMovie * qVariantToPointerToQMovie( const QVariant & variant ) const;


  private: // member variables

    mutable QAbstractItemView & view_;
};

#endif // MOVIEDELEGATE_HPP


// Definition

#include "movieDelegate.hpp"

#include <QtCore/QVariant>
#include <QtGui/QAbstractItemView>
#include <QtGui/QLabel>
#include <QtGui/QMovie>


Q_DECLARE_METATYPE( QMovie * )


//---------------------------------------------------------
// Public member functions
//---------------------------------------------------------

MovieDelegate::MovieDelegate( QAbstractItemView & view, QObject * parent )
  : QStyledItemDelegate( parent ), view_( view )
{
}


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

    const QVariant & data = index.data( Qt::DecorationRole );

    QMovie * movie = qVariantToPointerToQMovie( data );

    if ( ! movie )
    {
        view_.setIndexWidget( index, NULL );
    }
    else
    {
        QObject * indexWidget = view_.indexWidget( index );
        QLabel  * movieLabel  = qobject_cast< QLabel * >( indexWidget );

        if ( movieLabel )
        {
            // Reuse existing label

            if ( movieLabel->movie() != movie )
            {
                movieLabel->setMovie( movie );
            }
        }
        else
        {
            // Create new label;

            movieLabel = new QLabel;

            movieLabel->setMovie( movie );

            view_.setIndexWidget( index, movieLabel );
        }
    }
}


//---------------------------------------------------------
// Private member functions
//---------------------------------------------------------

QMovie * MovieDelegate::qVariantToPointerToQMovie( const QVariant & variant ) const
{
    if ( ! variant.canConvert< QMovie * >() ) return NULL;

    return variant.value< QMovie * >();
}