如何优化一个QStyledItemDelegate继承类的paint方法 - QTCN开发网

#ifndef MULTIIMAGESDELEGATE_H
#define MULTIIMAGESDELEGATE_H

#include <QStyledItemDelegate>
#include <QString>
#include <QObject>
#include <QPainter>
#include <QModelIndex>
#include <QStyle>
#include <QStringList>
#include <QPixmap>
#include <QImage>
#include <QRect>
#include <QSize>
#include <QFile>

class MultiImagesDelegate : public QStyledItemDelegate
{
    Q_OBJECT

public:
    MultiImagesDelegate(QObject *parent = 0);
    MultiImagesDelegate(const QString &imagesFolder, QObject *parent = 0);

    void setImagesFolder(const QString &imagesFolder);

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

    QSize sizeHint(const QStyleOptionViewItem &option,
                   const QModelIndex &index) const override;

private:
     QString mImagesFolder;
     mutable int mWidthHint;
     enum {ImageMargin = 1};
};

#endif

#include "multiimagesdelegate.h"

MultiImagesDelegate::MultiImagesDelegate(QObject *parent) :
    QStyledItemDelegate(parent)
{
    mWidthHint = 200;
}

MultiImagesDelegate::MultiImagesDelegate(const QString &imagesFolder, QObject *parent) :
    QStyledItemDelegate(parent)
{
    setImagesFolder(imagesFolder);
}

//设置图片所在的文件夹
void MultiImagesDelegate::setImagesFolder(const QString &imagesFolder)
{
    mImagesFolder = imagesFolder;
}

void MultiImagesDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
                         const QModelIndex &index) const
{
    //painter->save();
    painter->setRenderHint(QPainter::Antialiasing);
    //如果是用户选择的行，则用高亮色绘制背景
    if (option.state & QStyle::State_Selected)
        painter->fillRect(option.rect, option.palette.highlight());

    //把model里的图片文件字符串拆分为一个QStringList
    QStringList images = index.data().toString().split(";");
    //绘制每张图片的x位移量，初始值从0开始
    int xOffsetForAdjust = 0;

    QRect optionRect = option.rect;

    //遍历图片文件名，并绘制图片
    for (int i = 0; i < images.count(); ++i) {

        QString imageFileName(mImagesFolder + images.at(i));
        if (QFile(imageFileName).exists()) {
            //加载图片
            QImage individualImage = QImage(imageFileName);
            //按行高对图片进行尺寸调整
            QImage scaledIndividualImage = individualImage.scaledToHeight(optionRect.height());

            //调整后的实际图片宽度和高度
            int scaledWidthOfImage = scaledIndividualImage.width();
            int scaledHeightOfImage = scaledIndividualImage.height();

            //定义绘制图片的矩形
            QRect imageRect(optionRect);
            imageRect.setWidth(scaledWidthOfImage);
            imageRect.setHeight(scaledHeightOfImage);

            //按照已经绘制的图片大小以及当前图片的大小调整当前图片绘制矩形的位置
            imageRect.adjust(xOffsetForAdjust + ImageMargin, ImageMargin * 2,
                             xOffsetForAdjust - ImageMargin, -ImageMargin * 2);
            //把当前图片的宽度加到总的x位移量，用于下一张图片的绘制
            xOffsetForAdjust += scaledWidthOfImage;

            //绘制当前图片
            painter->drawImage(imageRect, scaledIndividualImage);

            //计算所有已经绘制的图片的宽度，用于sizHint
            int totalWidth = imageRect.right() - optionRect.left() + ImageMargin * 2;
            if (totalWidth > mWidthHint)  //?? 当尺寸变小后，此方法不适用
                mWidthHint = totalWidth;
        }
    }
    //painter->restore();
}

QSize MultiImagesDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    Q_UNUSED(option);
    Q_UNUSED(index);
    return QSize(mWidthHint,100);
}