模型视图委托(MVD)是Qt中特有的设计模式,类似MVC设计模式,将MVC设计模式中的Controller当做MVD中的Delegate,两者的概念基本相同。不同的是委托不是独立存在,而是包含在视图里面。 模型视图委托设计模式中,模型负责存储和管理数据;视图负责显示数据,其中界面的框架和基础信息是视图负责,具体数据的显示是委托负责;委托不仅仅负责数据的显示,还有一个重要的功能是负责数据的编辑,如在视图中双击就可以编辑数据。
一、MVD简介
QT当中model-view-delegate(模型-视图-代理),此结构实现数据和界面的分离。
Qt的模型-视图结构分为三部分:模型(mode)-视图(view)-代理(Delegate) ,其中模型与数据源通信,并为其它部件提供接口;视图从模型中引用数据条的模型索引(Modellndex),在视图当中,代理负责绘制数据条目,比如编辑条目,代理和模型进行直接通信。
1、模型 (model): 实现自定义模型可以通过QAbstractltemModel类继承,也可以通过QAbstractListModel和QAbstractTableModel类继承实现列表模型或者表格模型
2、视图(view): 实现自定义的视图View,可以继承子QAbstractltemView类,对所需要的虚拟函数进行重定义。
3、代理 (delegate) :在表格当中嵌入各种不同的控件,通过表格中控件对编辑的内容进行操作。表格插入控件方式,控件始终显示。
二、简述
本实例基于QT的委托代理机制实现的Qt模型视图代理(Model-View-Delegate)使用示例。以QTableView为基础,实现表头排序,列表复选框,插入按钮、下拉框、进度条。在Qt中,QTableView是一个用于显示表格数据的控件,可以使用Qt的模型视图代理(Model-View-Delegate)设计模式来定制QTableView的外观和行为。
三、效果
四、核心代码
student.h 学生信息
#ifndef STUDENT_H
#define STUDENT_H
#include <QtCore>
struct Student
{
bool checked = false;
quint16 id = 0;
QString name;
quint16 age = 0;
QString gender = QObject::tr("男");
quint16 achievement= 0;
qint16 process = 50;
};
Q_DECLARE_METATYPE(Student);//将自定义类型声明为元类型(MetaType),以便在信号与槽机制中通过传递
Q_DECLARE_METATYPE(Student*);
#endif // STUDENT_H
1、下拉框委托类
comboboxdelegate.h
#ifndef COMBOBOXDELEGATE_H
#define COMBOBOXDELEGATE_H
#include <QStyledItemDelegate>
//下拉框委托类
class ComboBoxDelegate : public QStyledItemDelegate
{
Q_OBJECT
public:
explicit ComboBoxDelegate(QObject *parent = nullptr)
: QStyledItemDelegate(parent)
{}
protected:
QWidget *createEditor(QWidget *parent,
const QStyleOptionViewItem &,
const QModelIndex &) const Q_DECL_OVERRIDE;
void setEditorData(QWidget *editor, const QModelIndex &index) const Q_DECL_OVERRIDE;
void setModelData(QWidget *editor,
QAbstractItemModel *model,
const QModelIndex &index) const Q_DECL_OVERRIDE;
};
#endif // COMBOBOXDELEGATE_H
comboboxdelegate.cpp
#include "comboboxdelegate.h"
#include "student.h"
#include <QtWidgets>
QWidget *ComboBoxDelegate::createEditor(QWidget *parent,
const QStyleOptionViewItem &,
const QModelIndex &) const
{
QComboBox *comboBox = new QComboBox(parent);
comboBox->addItems(QStringList() << tr("男") << tr("女"));
return comboBox;
}
void ComboBoxDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
QComboBox *comboBox = qobject_cast<QComboBox *>(editor);
comboBox->setCurrentIndex(index.data(Qt::EditRole).toInt());
}
void ComboBoxDelegate::setModelData(QWidget *editor,
QAbstractItemModel *model,
const QModelIndex &index) const
{
QComboBox *comboBox = qobject_cast<QComboBox *>(editor);
model->setData(index, comboBox->currentText(), Qt::EditRole);
}
2、按钮委托类
buttondelegate.h
#ifndef BUTTONDELEGATE_H
#define BUTTONDELEGATE_H
#include <QStyledItemDelegate>
//按钮委托类
class ButtonDelegate : public QStyledItemDelegate
{
public:
ButtonDelegate(QObject* parent = nullptr);
void paint(QPainter *painter,
const QStyleOptionViewItem &option,
const QModelIndex &index) const override;
protected:
bool editorEvent(QEvent *event, QAbstractItemModel *model,
const QStyleOptionViewItem &option,
const QModelIndex &index) override;
private:
QScopedPointer<QStyleOptionButton> m_buttonPtr;
};
#endif // BUTTONDELEGATE_H
buttondelegate.cpp
#include "buttondelegate.h"
#include "student.h"
#include <QPainter>
#include <QApplication>
#include <QMouseEvent>
#include <QtWidgets>
ButtonDelegate::ButtonDelegate(QObject *parent)
: QStyledItemDelegate(parent)
, m_buttonPtr(new QStyleOptionButton)
{
}
void ButtonDelegate::paint(QPainter *painter,
const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
int w = qMin(option.rect.width(), option.rect.height()) / 10.0;
m_buttonPtr->rect = option.rect.adjusted(w, w, -w, -w);
m_buttonPtr->text = index.model()->data(index).toString();
m_buttonPtr->state |= QStyle::State_Enabled;
painter->save();
if (option.state & QStyle::State_Selected) {
painter->fillRect(option.rect, option.palette.highlight());
painter->setBrush(option.palette.highlightedText());
}
QPushButton button;
qApp->style()->drawControl(QStyle::CE_PushButton, m_buttonPtr.data(), painter, &button);
painter->restore();
}
bool ButtonDelegate::editorEvent(QEvent *event,
QAbstractItemModel *model,
const QStyleOptionViewItem &option,
const QModelIndex &index)
{
int w = qMin(option.rect.width(), option.rect.height()) / 10.0;
switch (event->type()) {
case QEvent::MouseButtonPress:{
QMouseEvent* mouseEvent =(QMouseEvent*)event;
if (option.rect.adjusted(w, w, -w, -w).contains(mouseEvent->pos())) {
m_buttonPtr->state |= QStyle::State_Sunken;
}
} break;
case QEvent::MouseButtonRelease:{
QMouseEvent* mouseEvent =(QMouseEvent*)event;
if (option.rect.adjusted(w, w, -w, -w).contains(mouseEvent->pos())) {
m_buttonPtr->state &= (~QStyle::State_Sunken);
Student* stu = model->data(index, Qt::UserRole).value<Student*>();
if(stu){
QString details = tr("This Student id = %1, name = %2, age = %3, "
"gender = %4, achievement = %5")
.arg(stu->id)
.arg(stu->name)
.arg(stu->age)
.arg(stu->gender)
.arg(stu->achievement);
QDialog dialog;
QHBoxLayout *layout = new QHBoxLayout(&dialog);
layout->addWidget(new QLabel(details, &dialog));
dialog.exec();
}
}
}
break;
default: break;
}
return true;
}
3、 进度条委托类
progressbardelegate.h
#ifndef PROGRESSBARDELEGATE_H
#define PROGRESSBARDELEGATE_H
#include <QStyledItemDelegate>
//进度条委托类
class ProgressBarDelegate : public QStyledItemDelegate
{
public:
ProgressBarDelegate(QObject* parent = nullptr) : QStyledItemDelegate(parent) {}
void paint(QPainter *painter,
const QStyleOptionViewItem &option,
const QModelIndex &index) const;
};
#endif // PROGRESSBARDELEGATE_H
progressbardelegate.cpp
#include "progressbardelegate.h"
#include <QPainter>
#include <QtWidgets>
void ProgressBarDelegate::paint(QPainter *painter,
const QStyleOptionViewItem &option,
const QModelIndex &index) const
{
QStyleOptionViewItem viewOption(option);
initStyleOption(&viewOption, index);
if (option.state.testFlag(QStyle::State_HasFocus))
viewOption.state = viewOption.state ^ QStyle::State_HasFocus;
QStyledItemDelegate::paint(painter, viewOption, index);
int value = index.model()->data(index).toUInt();
if (value < 0)
value = 0;
else if (value > 100)
value = 100;
int w = qMin(option.rect.width(), option.rect.height()) / 10.0;
QStyleOptionProgressBar progressBarOption;
progressBarOption.initFrom(option.widget);
progressBarOption.rect = option.rect.adjusted(w, w, -w, -w);
progressBarOption.minimum = 0;
progressBarOption.maximum = 100;
progressBarOption.textAlignment = Qt::AlignCenter;
progressBarOption.textVisible = true;
progressBarOption.progress = value;
progressBarOption.text = tr("%1%").arg(progressBarOption.progress);
painter->save();
if (option.state & QStyle::State_Selected) {
painter->fillRect(option.rect, option.palette.highlight());
painter->setBrush(option.palette.highlightedText());
}
QProgressBar progressBar;
qApp->style()->drawControl(QStyle::CE_ProgressBar, &progressBarOption, painter, &progressBar);
painter->restore();
}
4、排序代理
sortfilterproxymodel.h
#ifndef SORTFILTERPROXYMODEL_H
#define SORTFILTERPROXYMODEL_H
#include <QSortFilterProxyModel>
//排序代理
class SortFilterProxyModel : public QSortFilterProxyModel
{
public:
SortFilterProxyModel(QObject *parent = nullptr)
: QSortFilterProxyModel(parent) {}
protected:
bool lessThan(const QModelIndex &left, const QModelIndex &right) const override; //重定义排序规则
};
#endif // SORTFILTERPROXYMODEL_H
sortfilterproxymodel.cpp
#include "sortfilterproxymodel.h"
#include <QDateTime>
bool SortFilterProxyModel::lessThan(const QModelIndex &left, const QModelIndex &right) const
{
QVariant leftData = sourceModel()->data(left);
QVariant rightData = sourceModel()->data(right);
if (leftData.userType() == QMetaType::QDateTime) {
return leftData.toDateTime() < rightData.toDateTime();
} else if(leftData.userType() == QMetaType::Int) {
return leftData.toInt() > rightData.toInt();
}
QString leftString = leftData.toString();
QString rightString = rightData.toString();
return QString::localeAwareCompare(leftString, rightString) < 0;
}
5、学生数据表数据模型
studenttablemodel.h
#ifndef STUDENTTABLEMODEL_H
#define STUDENTTABLEMODEL_H
#include <QAbstractTableModel>
struct Student;
class StuedentTableModel : public QAbstractTableModel
{
Q_OBJECT
public:
explicit StuedentTableModel(QObject *parent = nullptr): QAbstractTableModel(parent){}
int rowCount(const QModelIndex & = QModelIndex()) const { return m_students.count(); }
int columnCount(const QModelIndex & = QModelIndex()) const { return 7; }
QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;
bool setData(const QModelIndex &index, const QVariant &value, int role = Qt::EditRole);
QVariant headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const;
Qt::ItemFlags flags(const QModelIndex &index) const;
void setStudents(const QList<Student *> &students);
private:
QList<Student *> m_students;
};
#endif // STUDENTTABLEMODEL_H
studenttablemodel.cpp
#include "studenttablemodel.h"
#include "student.h"
enum Property { ID, NAME, AGE, GENDER, ACHIEVEMENT, MENUBUTTON, PROCESS };
QVariant StuedentTableModel::data(const QModelIndex &index, int role) const
{
if (!index.isValid())
return false;
int row = index.row();
int col = index.column();
Student *stu = m_students.at(row);
switch (role) {
case Qt::TextAlignmentRole: return Qt::AlignCenter;
case Qt::CheckStateRole:
switch (col) {
case ID: return stu->checked;
default: break;
}
break;
case Qt::DisplayRole:
case Qt::EditRole: { //双击为空需添加
switch (col) {
case ID: return stu->id;
case NAME: return stu->name;
case AGE: return stu->age;
case GENDER: return stu->gender;
case ACHIEVEMENT: return stu->achievement;
case MENUBUTTON: return tr("Detail");
case PROCESS: return stu->process;
default: break;
}
case Qt::UserRole: {
switch (col) {
case MENUBUTTON: return QVariant::fromValue(stu);
default: break;
}
}
}
default: break;
}
return QVariant();
}
bool StuedentTableModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
if (!index.isValid())
return false;
int row = index.row();
int col = index.column();
Student *stu = m_students[row];
switch (role) {
case Qt::CheckStateRole:
switch (col) {
case ID:
stu->checked = !stu->checked;
emit dataChanged(index, index);
return true;
default: break;
}
break;
case Qt::EditRole:
switch (col) {
case ID: stu->id = value.toUInt(); break;
case NAME: stu->name = value.toString(); break;
case AGE: stu->age = value.toUInt(); break;
case GENDER: stu->gender = value.toString(); break;
case ACHIEVEMENT: stu->achievement = value.toUInt(); break;
case PROCESS: stu->process = value.toUInt(); break;
}
emit dataChanged(index, index);
return true;
default: break;
}
return false;
}
QVariant StuedentTableModel::headerData(int section, Qt::Orientation orientation, int role) const
{
const QStringList names = {tr("ID"),
tr("姓名"),
tr("年龄"),
tr("性别"),
tr("成绩"),
tr("详情"),
tr("进度")};
if (section < 0 || section >= names.size())
return QVariant();
if (orientation == Qt::Horizontal && role == Qt::DisplayRole)
return names.at(section);
return QVariant();
}
Qt::ItemFlags StuedentTableModel::flags(const QModelIndex &index) const
{
Qt::ItemFlags flags = QAbstractTableModel::flags(index);
flags |= Qt::ItemIsEditable;
if (index.column() == ID)
flags |= Qt::ItemIsUserCheckable;
return flags;
}
void StuedentTableModel::setStudents(const QList<Student *> &students)
{
beginResetModel(); //重置数据之前调用,会自动触发 modelAboutToBeReset 信号
m_students = students;
endResetModel(); //重置数据完成后调用,会自动触发 modelReset 信号
}
6、学生数据表
stuedenttable.h
#ifndef STUDENTTABLE_H
#define STUDENTTABLE_H
#include <QAbstractTableModel>
#include <QStyledItemDelegate>
#include <QTableView>
struct Student;
class StuedentTableModel;
class StudentsTable : public QTableView
{
Q_OBJECT
public:
StudentsTable(QWidget *parent = nullptr);
void setStudents(const QList<Student *> &students);
protected:
void contextMenuEvent(QContextMenuEvent *event) override;
signals:
void insertItem();
void removeItem();
private:
void initMenu();
StuedentTableModel *m_stuModel;
QMenu *m_menu;
};
#endif // STUDENTTABLE_H
stuedenttable.cpp
#include "stuedenttable.h"
#include "buttondelegate.h"
#include "comboboxdelegate.h"
#include "progressbardelegate.h"
#include "sortfilterproxymodel.h"
#include "studenttablemodel.h"
#include <QtWidgets>
StudentsTable::StudentsTable(QWidget *parent)
: QTableView(parent)
, m_stuModel(new StuedentTableModel(this))
, m_menu(new QMenu(this))
{
setShowGrid(true);
setWordWrap(false);
setAlternatingRowColors(true);
verticalHeader()->setVisible(false);
verticalHeader()->setDefaultSectionSize(30);
horizontalHeader()->setStretchLastSection(true);
horizontalHeader()->setDefaultSectionSize(90);
horizontalHeader()->setMinimumSectionSize(35);
horizontalHeader()->setSectionResizeMode(QHeaderView::Interactive);
setSelectionBehavior(QAbstractItemView::SelectItems);
setSelectionMode(QAbstractItemView::SingleSelection);
setContextMenuPolicy(Qt::DefaultContextMenu);
//设置委托
setItemDelegateForColumn(3, new ComboBoxDelegate(this)); //下拉框
setItemDelegateForColumn(5, new ButtonDelegate(this)); //按钮
setItemDelegateForColumn(6, new ProgressBarDelegate(this)); //进度条
//设置代理实现自定义排序
setSortingEnabled(true);
SortFilterProxyModel *sortModel = new SortFilterProxyModel(this);
sortModel->setSourceModel(m_stuModel);
setModel(sortModel);
initMenu();
}
void StudentsTable::setStudents(const QList<Student *> &students)
{
m_stuModel->setStudents(students);
}
void StudentsTable::contextMenuEvent(QContextMenuEvent *event)
{
if (!currentIndex().isValid())
return;
m_menu->exec(mapToGlobal(event->pos()));
}
void StudentsTable::initMenu()
{
m_menu->addAction(tr("insert"), this, &StudentsTable::insertItem);
m_menu->addAction(tr("remove"), this, &StudentsTable::removeItem);
m_menu->addAction(tr("rename"), this, [this] { edit(currentIndex().siblingAtColumn(0)); });
}
五、使用示例
以下是一个简单的示例代码,演示了如何在Qt中使用StudentsTable控件:
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
struct Student;
class StudentsTable;
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void onInsertItem();
void onRemoveItem();
private:
void init();
void setupUI();
StudentsTable *m_table;
QList<Student *> m_students;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "student.h"
#include "studenttablemodel.h"
#include "stuedenttable.h"
#include <QtWidgets>
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
setupUI();
init();
resize(800, 300);
}
MainWindow::~MainWindow()
{
if (!m_students.isEmpty()) {
qDeleteAll(m_students);
m_students.clear();
}
}
void MainWindow::onInsertItem()
{
int row = m_table->currentIndex().row();
Student *stu = new Student;
stu->id = m_students.size();
if (row < 0 || row >= m_students.size())
m_students.append(stu);
else
m_students.insert(row, stu);
m_table->setStudents(m_students);
}
void MainWindow::onRemoveItem()
{
QModelIndex index = m_table->currentIndex();
if (!index.isValid())
return;
int row = index.row();
delete m_students.takeAt(row);
m_table->setStudents(m_students);
}
void MainWindow::init()
{
m_students.append(new Student{true, 0, "Jason", 15, "男", 66, 10});
m_students.append(new Student{false, 1, "Lily", 13, "女", 85, 20});
m_students.append(new Student{true, 2, "Odin", 16, "女", 76, 30});
m_students.append(new Student{false, 3, "Willion", 12, "男", 89, 40});
m_students.append(new Student{true, 4, "Nieo", 14, "男", 77, 50});
m_table->setStudents(m_students);
m_table->selectRow(m_students.size() - 1);
}
void MainWindow::setupUI()
{
QPushButton *addBtn = new QPushButton(tr("增加"), this);
QPushButton *removeBtn = new QPushButton(tr("删除"), this);
m_table = new StudentsTable(this);
QHBoxLayout *hLayout = new QHBoxLayout;
hLayout->addStretch(1);
hLayout->addWidget(addBtn);
hLayout->addWidget(removeBtn);
QVBoxLayout *layout = new QVBoxLayout;
layout->addLayout(hLayout);
layout->addWidget(m_table);
QFrame *frame = new QFrame(this);
frame->setLayout(layout);
setCentralWidget(frame);
connect(m_table, &StudentsTable::insertItem, this, &MainWindow::onInsertItem);
connect(m_table, &StudentsTable::removeItem, this, &MainWindow::onRemoveItem);
connect(addBtn, &QPushButton::clicked, this, &MainWindow::onInsertItem);
connect(removeBtn, &QPushButton::clicked, this, &MainWindow::onRemoveItem);
}
到此本文基于QTableView的Model View Delegate使用方法就介绍到这了。
总的来说,Qt的模型视图代理提供了一种灵活的方式来显示和编辑数据,在处理大量数据和复杂数据结构时特别有用。它将数据与界面分离,使得数据的表示和样式能够独立于数据本身进行修改。这种模式不仅提高了开发效率,还使得代码更加清晰和易于维护。
谢谢您的阅读,希望本文能为您带来一些帮助和启发。如果您有任何问题或意见,请随时与我联系。祝您度过美好的一天!