Qt浅谈之十九：Model/View实现表格和统计图

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一、简介

Model/View结构使数据管理与相应的数据显示相互独立，并提供了一系列标准的函数接口和用于Model模块与View模块之间的通信。它从MVC演化而来，MVC由三种对象组成，Model是应用程序对象，View是它的屏幕表示，Controller定义了用户界面如何对用户输入进行响应。把MVC中的View和Controller合在一起，就形成了Model/View结构。

二、运行图

（1）为了灵活对用户的输入进行处理，引入了Delegate，Model、View、Delegate三个模块之间通过信号与槽机制实现，当自身的状态发生改变时会发出信号通知其他模块。它们间的关系如下图1所示。

QAbstractItemModel是所有Model的基类，但一般不直接使用QAbstractItemModel，而是使用它的子类。Model模块本身并不存储数据，而是为View和Delegate访问数据提供标准的接口。

View模块从Model中获得数据项显示给用户，Qt提供了一些常用的View模型，如QTreeView、QTableView和QListView。

Delegate的基本接口在QAbstractItemDelegate类中定义，通过实现paint()和sizeHint()以达到渲染数据项的目的。

（2）程序运行图如下图2所示。

三、详解

1、表格中嵌入控件

利用Delegate的方式实现表格中嵌入各种不同控件的效果，控件在需要编辑数据项时才出现。

（1）插入日历编辑框QDateLineEdit

#ifndef DATEDELEGATE_H
#define DATEDELEGATE_H#include <QtGui>class DateDelegate : public QItemDelegate
{Q_OBJECTpublic:DateDelegate(QObject *parent = 0);QWidget *createEditor(QWidget *parent, const QStyleOptionViewItem &option,const QModelIndex &index) const;void setEditorData(QWidget *editor, const QModelIndex &index) const;void setModelData(QWidget *editor, QAbstractItemModel *model,const QModelIndex &index) const;void updateEditorGeometry(QWidget *editor,const QStyleOptionViewItem &option, const QModelIndex &index) const;
};#endif

#include "datedelegate.h"DateDelegate::DateDelegate(QObject *parent): QItemDelegate(parent)
{
}QWidget *DateDelegate::createEditor(QWidget *parent,const QStyleOptionViewItem &/* option */,const QModelIndex &/* index */) const
{QDateTimeEdit *editor = new QDateTimeEdit(parent);editor->setDisplayFormat("yyyy-MM-dd");editor->setCalendarPopup(true);editor->installEventFilter(const_cast<DateDelegate*>(this));return editor;
}void DateDelegate::setEditorData(QWidget *editor,const QModelIndex &index) const
{QString dateStr = index.model()->data(index).toString();QDate date = QDate::fromString(dateStr,Qt::ISODate);QDateTimeEdit *edit = static_cast<QDateTimeEdit*>(editor);edit->setDate(date);
}void DateDelegate::setModelData(QWidget *editor, QAbstractItemModel *model,const QModelIndex &index) const
{QDateTimeEdit *edit = static_cast<QDateTimeEdit*>(editor);QDate date = edit->date();model->setData(index, QVariant(date.toString(Qt::ISODate)));
}void DateDelegate::updateEditorGeometry(QWidget *editor,const QStyleOptionViewItem &option, const QModelIndex &/* index */) const
{editor->setGeometry(option.rect);
}

分析：DateDelegate继承QItemDelegate，一般需要重定义声明中的几个虚函数。createEditor()函数完成创建控件的工作；setEditorDate()设置控件显示的数据，把Model数据更新至Delegate，相当于初始化工作；setModelDate()把Delegate中对数据的更改更新至Model中；updateEditor()更析控件区的显示。

（2）插入下拉列表框QComboBox

#include "combodelegate.h"ComboDelegate::ComboDelegate(QObject *parent): QItemDelegate(parent)
{
}QWidget *ComboDelegate::createEditor(QWidget *parent,const QStyleOptionViewItem &/* option */,const QModelIndex &/* index */) const
{QComboBox *editor = new QComboBox(parent);editor->addItem(QString::fromLocal8Bit("工人"));editor->addItem(QString::fromLocal8Bit("农民"));editor->addItem(QString::fromLocal8Bit("医生"));editor->addItem(QString::fromLocal8Bit("律师"));editor->addItem(QString::fromLocal8Bit("军人"));editor->installEventFilter(const_cast<ComboDelegate*>(this));return editor;
}void ComboDelegate::setEditorData(QWidget *editor,const QModelIndex &index) const
{QString str = index.model()->data(index).toString();QComboBox *box = static_cast<QComboBox*>(editor);int i = box->findText(str);box->setCurrentIndex(i);
}void ComboDelegate::setModelData(QWidget *editor, QAbstractItemModel *model,const QModelIndex &index) const
{QComboBox *box = static_cast<QComboBox*>(editor);QString str = box->currentText();model->setData(index, str);
}void ComboDelegate::updateEditorGeometry(QWidget *editor,const QStyleOptionViewItem &option, const QModelIndex &/* index */) const
{editor->setGeometry(option.rect);
}

（3）插入微调器QSpinBox

#include "spindelegate.h"SpinDelegate::SpinDelegate(QObject *parent): QItemDelegate(parent)
{
}QWidget *SpinDelegate::createEditor(QWidget *parent,const QStyleOptionViewItem &/* option */,const QModelIndex &/* index */) const
{QSpinBox *editor = new QSpinBox(parent);editor->setRange(1000,10000);    editor->installEventFilter(const_cast<SpinDelegate*>(this));return editor;
}void SpinDelegate::setEditorData(QWidget *editor,const QModelIndex &index) const
{int value = index.model()->data(index).toInt();QSpinBox *spin = static_cast<QSpinBox*>(editor);spin->setValue(value);
}void SpinDelegate::setModelData(QWidget *editor, QAbstractItemModel *model,const QModelIndex &index) const
{QSpinBox *spin = static_cast<QSpinBox*>(editor);int value = spin->value();model->setData(index, value);
}void SpinDelegate::updateEditorGeometry(QWidget *editor,const QStyleOptionViewItem &option, const QModelIndex &/* index */) const
{editor->setGeometry(option.rect);
}

2、柱状统计图

自定义的View实现一个柱状统计图对TableModel的表格数据进行显示。

#ifndef HISTOGRAMVIEW_H
#define HISTOGRAMVIEW_H#include <QtGui>class HistogramView : public QAbstractItemView
{Q_OBJECT
public:HistogramView(QWidget *parent=0);QRect visualRect(const QModelIndex &index)const;void scrollTo(const QModelIndex &index, ScrollHint hint = EnsureVisible);QModelIndex indexAt(const QPoint &point) const;    void paintEvent(QPaintEvent *);void mousePressEvent(QMouseEvent *);void setSelectionModel(QItemSelectionModel * selectionModel);QRegion itemRegion(QModelIndex index);  protected slots:void dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight);void selectionChanged(const QItemSelection & selected, const QItemSelection & deselected );protected:QModelIndex moveCursor(QAbstractItemView::CursorAction cursorAction,Qt::KeyboardModifiers modifiers);int horizontalOffset() const;int verticalOffset() const;    bool isIndexHidden(const QModelIndex &index) const;void setSelection ( const QRect&rect, QItemSelectionModel::SelectionFlags flags );QRegion visualRegionForSelection(const QItemSelection &selection) const;       private:QItemSelectionModel *selections; QList<QRegion> listRegionM;  QList<QRegion> listRegionF; QList<QRegion> listRegionS; };#endif

#include "histogramview.h"HistogramView::HistogramView(QWidget *parent): QAbstractItemView(parent)
{}void HistogramView::dataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight)
{QAbstractItemView::dataChanged(topLeft, bottomRight);viewport()->update();
}QRect HistogramView::visualRect(const QModelIndex &index) const
{}void HistogramView::scrollTo(const QModelIndex &index, ScrollHint hint)
{}QModelIndex HistogramView::indexAt(const QPoint &point) const
{QPoint newPoint(point.x(),point.y());QRegion region;foreach(region,listRegionM){if (region.contains(newPoint)){int row = listRegionM.indexOf(region);QModelIndex index = model()->index(row, 3,rootIndex());return index;}}return QModelIndex();
}QModelIndex HistogramView::moveCursor(QAbstractItemView::CursorAction cursorAction,Qt::KeyboardModifiers modifiers)
{}int HistogramView::horizontalOffset() const
{
}int HistogramView::verticalOffset() const
{}bool HistogramView::isIndexHidden(const QModelIndex &index) const
{}void HistogramView::setSelectionModel(QItemSelectionModel * selectionModel)
{selections = selectionModel;
}void HistogramView::mousePressEvent(QMouseEvent *e)
{QAbstractItemView::mousePressEvent(e);setSelection(QRect(e->pos().x(),e->pos().y(),1,1),QItemSelectionModel::SelectCurrent);    
}QRegion HistogramView::itemRegion(QModelIndex index)
{QRegion region;if (index.column() == 3)region = listRegionM[index.row()];return region;
}void HistogramView::setSelection ( const QRect &rect, QItemSelectionModel::SelectionFlags flags )
{int rows = model()->rowCount(rootIndex());int columns = model()->columnCount(rootIndex());QModelIndex selectedIndex;for (int row = 0; row < rows; ++row) {for (int column = 1; column < columns; ++column) {QModelIndex index = model()->index(row, column, rootIndex());QRegion region = itemRegion(index);if (!region.intersected(rect).isEmpty())selectedIndex = index;}}if(selectedIndex.isValid()) selections->select(selectedIndex,flags);else {QModelIndex noIndex;selections->select(noIndex, flags);}
}QRegion HistogramView::visualRegionForSelection(const QItemSelection &selection) const
{}void HistogramView::selectionChanged(const QItemSelection & selected, const QItemSelection & deselected )
{viewport()->update();
}void HistogramView::paintEvent(QPaintEvent *)
{QPainter painter(viewport());painter.setPen(Qt::black);int x0 = 40;int y0 = 250;// draw coordinate  painter.drawLine(x0, y0, 40, 30);painter.drawLine(38, 32, 40, 30);painter.drawLine(40, 30, 42, 32);painter.drawText(5, 45, tr("income"));for (int i=1; i<5; i++) {painter.drawLine(-1,-i*50,1,-i*50);painter.drawText(-20,-i*50,tr("%1").arg(i*5));}// x轴painter.drawLine(x0, y0, 540, 250);painter.drawLine(538, 248, 540, 250);painter.drawLine(540, 250, 538, 252);painter.drawText(500, 270, tr("name"));int row;// nameint posD = x0+20;for (row = 0; row < model()->rowCount(rootIndex()); row++) {QModelIndex index = model()->index(row, 0, rootIndex());QString dep = model()->data(index).toString();    painter.drawText(posD,y0+20,dep);posD += 50;}// incomeint posM = x0+20;for (row = 0; row < model()->rowCount(rootIndex()); row++){QModelIndex index = model()->index(row, 3, rootIndex());int income = model()->data(index).toDouble();int width = 10;if (selections->isSelected(index))painter.setBrush(QBrush(Qt::darkBlue,Qt::SolidPattern));elsepainter.setBrush(Qt::blue);painter.drawRect(QRectF(posM + 10, y0-income/25, width, income/25));QRegion regionM(posM + 10, y0-income/25, width, income/25);listRegionM << regionM;posM += 50;}
}

分析：对父类的QAbstractItemView中的所有纯虚函数都必须进行声明，纯虚函数包括visualRect()、scrollTo()、indexAt()、moveCursor()、horizontalOffset()、verticalOffset()、isIndexHidden()、setSelection()和visualRegionForSelection()，这些函数并不一定都要实现，根据功能要求选择实现。