Qt中有几种纯粹的视图部件：QListView、QTableView、QColumnView、QTreeView，所有的这些视图都必须提供一个模型（无论是自定义，还是Qt中已提供的）来与之配合。Qt仍然提供了一些便利的窗口部件（“便利”是因为它们提供了自己内置的模型，并能直接使用），如：QListWidget、QTableWidget、和QTreeWidget。还有QComboBox，既是一个便利的窗口部件也是一个视图部件，也就是说，我们既可以直接使用（因为它提供了内置的模型），也能把它当做一个模型的视图部件（这种情况下，可以提供一个合适的模型给它）。

    之所以说视图部件常用，是因为在编程的过程当中经常遇到大数据集，使用视图/模型就显得更有效率。当然，对于数据集较小（数百或数千个项）的应用程序，选择便利部件比较合适。

模型/视图篇

（1）QTreeView节点项

#include 
#include "treeitem.h"

TreeItem::TreeItem(const QList &data, TreeItem *parent)
{
    parentItem = parent;
    itemData = data;
}

TreeItem::~TreeItem()
{
    qDeleteAll(childItems);
}

void TreeItem::a(TreeItem *item)
{
    childItems.append(item);
}

TreeItem *TreeItem::child(int row)
{
    return childItems.value(row);
}

int TreeItem::childCount() const
{
    return childItems.count();
}

int TreeItem::columnCount() const
{
    return itemData.count();
}

QVariant TreeItem::data(int column) const
{
    return itemData.value(column);
}

TreeItem *TreeItem::parent()
{
    return parentItem;
}

int TreeItem::row() const
{
    if (parentItem)
        return parentItem->childItems.indexOf(const_cast(this));

    return 0;
}

（2）QAbstractItemModel模型

#include "treeitem.h"
#include "treemodel.h"
#include 
#include 

TreeModel::TreeModel(QObject *parent)
    : QAbstractItemModel(parent)
{
    QList rootData;
    rootData << "Title";
    rootItem = new TreeItem(rootData);
}

TreeModel::~TreeModel()
{
    delete rootItem;
}

void TreeModel::setXML(QString xmlFile)
{
    toolList = Util::parse(xmlFile);
    setupModelData(rootItem);
}

int TreeModel::columnCount(const QModelIndex &parent) const
{
    if (parent.isValid())
        return static_cast(parent.internalPointer())->columnCount();
    else
        return rootItem->columnCount();
}

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

    TreeItem *item = static_cast(index.internalPointer());

    ToolUtil toolUtil;
    for (int i = 0; i < toolList.count(); ++i)
    {
        toolUtil = toolList.at(i);
        if (toolUtil.id == item->data(0))
        {
            break;
        }
    }

    if (role == Qt::DisplayRole)
    {
        return toolUtil.text;
    }
    else if (role == Qt::DecorationRole)
    {
        return QIcon(Util::exePath() + "\\Resources\\toolicon\\" + toolUtil.toolicon);
    }
    else if (role == Qt::ToolTipRole)
    {
        return toolUtil.tooltip;
    }
    else
    {
        return QVariant();
    }
}

Qt::ItemFlags TreeModel::flags(const QModelIndex &index) const
{
    if (!index.isValid())
        return 0;

    return QAbstractItemModel::flags(index);
}

QVariant TreeModel::headerData(int section, Qt::Orientation orientation,
                               int role) const
{
    if (orientation == Qt::Horizontal && role == Qt::DisplayRole)
        return rootItem->data(section);

    return QVariant();
}

QModelIndex TreeModel::index(int row, int column, const QModelIndex &parent)
            const
{
    if (!hasIndex(row, column, parent))
        return QModelIndex();

    TreeItem *parentItem;

    if (!parent.isValid())
        parentItem = rootItem;
    else
        parentItem = static_cast(parent.internalPointer());

    TreeItem *childItem = parentItem->child(row);
    if (childItem)
        return createIndex(row, column, childItem);
    else
        return QModelIndex();
}

QModelIndex TreeModel::parent(const QModelIndex &index) const
{
    if (!index.isValid())
        return QModelIndex();

    TreeItem *childItem = static_cast(index.internalPointer());
    TreeItem *parentItem = childItem->parent();

    if (parentItem == rootItem)
        return QModelIndex();

    return createIndex(parentItem->row(), 0, parentItem);
}

int TreeModel::rowCount(const QModelIndex &parent) const
{
    TreeItem *parentItem;
    if (parent.column() > 0)
        return 0;

    if (!parent.isValid())
        parentItem = rootItem;
    else
        parentItem = static_cast(parent.internalPointer());

    return parentItem->childCount();
}

TreeItem * TreeModel::item(TreeItem* item, ToolUtil tool)
{
    TreeItem *treeItem = NULL;
    if (item == NULL)
    {
        return treeItem;
    }

    int parentId = tool.parentId;

    if (item->data(0) == parentId)
    {
        treeItem = item;
    }
    else
    {
        for (int j = 0; j < item->childCount(); ++j)
        {
            TreeItem *childItem = item->child(j);
            TreeItem *item2 = this->item(childItem, tool);
            if (item2)
            {
                treeItem = item2;
                break;
            }
        }
    }

    return treeItem;
}

void TreeModel::setupModelData(TreeItem *parent)
{
    QList parents;
    parents << parent;

    for (int i = 0; i < toolList.count(); ++i)
    {
        ToolUtil tool = toolList.at(i);
        QList columnData;
        columnData << tool.id;

        for(int j = 0; j < parents.count(); ++j)
        {

            TreeItem* item = this->item(parents.at(j), tool);
            if (item)
            {
                item->a(new TreeItem(columnData, item));
            }
            else
            {
                parents.last()->a(new TreeItem(columnData, parents.last()));
            }
        }
    }
}

    前几章已经对模型中的方法解释的很清楚了，所以这里就不再过多阐述！