请高人给出下面关于拼图代码的详细解释，最好具体到每行

Question

#include

#include "piecesmodel.h"

PiecesModel::PiecesModel(int pieceSize, QObject *parent)
: QAbstractListModel(parent), m_PieceSize(pieceSize)
{
}

QVariant PiecesModel::data(const QModelIndex &index, int role) const
{
if (!index.isValid())
return QVariant();

if (role == Qt::DecorationRole)
    return QIcon(pixmaps.value(index.row()).scaled(m_PieceSize, m_PieceSize,
                     Qt::KeepAspectRatio, Qt::SmoothTransformation));
else if (role == Qt::UserRole)
    return pixmaps.value(index.row());
else if (role == Qt::UserRole + 1)
    return locations.value(index.row());

return QVariant();

}

void PiecesModel::addPiece(const QPixmap &pixmap, const QPoint &location)
{
int row;
if (int(2.0*qrand()/(RAND_MAX+1.0)) == 1)
row = 0;
else
row = pixmaps.size();

beginInsertRows(QModelIndex(), row, row);
pixmaps.insert(row, pixmap);
locations.insert(row, location);
endInsertRows();

}

Qt::ItemFlags PiecesModel::flags(const QModelIndex &index) const
{
if (index.isValid())
return (Qt::ItemIsEnabled | Qt::ItemIsSelectable | Qt::ItemIsDragEnabled);

return Qt::ItemIsDropEnabled;

}

bool PiecesModel::removeRows(int row, int count, const QModelIndex &parent)
{
if (parent.isValid())
return false;

if (row >= pixmaps.size() || row + count <= 0)
    return false;

int beginRow = qMax(0, row);
int endRow = qMin(row + count - 1, pixmaps.size() - 1);

beginRemoveRows(parent, beginRow, endRow);

while (beginRow <= endRow) {
    pixmaps.removeAt(beginRow);
    locations.removeAt(beginRow);
    ++beginRow;
}

endRemoveRows();
return true;

}

QStringList PiecesModel::mimeTypes() const
{
QStringList types;
types << "image/x-puzzle-piece";
return types;
}

QMimeData *PiecesModel::mimeData(const QModelIndexList &indexes) const
{
QMimeData *mimeData = new QMimeData();
QByteArray encodedData;

QDataStream stream(&encodedData, QIODevice::WriteOnly);

foreach (QModelIndex index, indexes) {
    if (index.isValid()) {
        QPixmap pixmap = qvariant_cast<QPixmap>(data(index, Qt::UserRole));
        QPoint location = data(index, Qt::UserRole+1).toPoint();
        stream << pixmap << location;
    }
}

mimeData->setData("image/x-puzzle-piece", encodedData);
return mimeData;

}

bool PiecesModel::dropMimeData(const QMimeData *data, Qt::DropAction action,
int row, int column, const QModelIndex &parent)
{
if (!data->hasFormat("image/x-puzzle-piece"))
return false;

if (action == Qt::IgnoreAction)
    return true;

if (column > 0)
    return false;

int endRow;

if (!parent.isValid()) {
    if (row < 0)
        endRow = pixmaps.size();
    else
        endRow = qMin(row, pixmaps.size());
} else
    endRow = parent.row();

QByteArray encodedData = data->data("image/x-puzzle-piece");
QDataStream stream(&encodedData, QIODevice::ReadOnly);

while (!stream.atEnd()) {
    QPixmap pixmap;
    QPoint location;
    stream >> pixmap >> location;

    beginInsertRows(QModelIndex(), endRow, endRow);
    pixmaps.insert(endRow, pixmap);
    locations.insert(endRow, location);
    endInsertRows();

    ++endRow;
}

return true;

}

int PiecesModel::rowCount(const QModelIndex &parent) const
{
if (parent.isValid())
return 0;
else
return pixmaps.size();
}

Qt::DropActions PiecesModel::supportedDropActions() const
{
return Qt::CopyAction | Qt::MoveAction;
}

void PiecesModel::addPieces(const QPixmap& pixmap)
{
beginRemoveRows(QModelIndex(), 0, 24);
pixmaps.clear();
locations.clear();
endRemoveRows();
for (int y = 0; y < 5; ++y) {
for (int x = 0; x < 5; ++x) {
QPixmap pieceImage = pixmap.copy(x*m_PieceSize, y*m_PieceSize, m_PieceSize, m_PieceSize);
addPiece(pieceImage, QPoint(x, y));
}
}
}

Answer 1

具体到行估计没人有这个时间 你把你不懂的问题抛出来