QT MVC 技术Model/View初探

发布时间：2020-07-29 12:08:05 作者：WZM3558862
来源：网络阅读：1490

Model/View实现表格技术

[+]

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。

QT MVC 技术Model/View初探

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。

QT MVC 技术Model/View初探

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

[cpp] view plain copy

#ifndef DATEDELEGATE_H
#define DATEDELEGATE_H
#include <QtGui>
class DateDelegate : public QItemDelegate
{
Q_OBJECT
public:
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

[cpp] view plain copy

#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

[cpp] view plain copy

#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

[cpp] view plain copy

#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。

[cpp] view plain copy

#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

[cpp] view plain copy

#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;
// name
int 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;
}
// income
int 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));
else
painter.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。

QT MVC 技术Model/View初探

Model/View实现表格技术

一、简介

二、运行图

三、详解

1、表格中嵌入控件

2、柱状统计图

相关阅读