模型/视图教程

// main.cpp
#include <QApplication>
#include <QTableView>
#include "mymodel.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QTableView tableView;
    MyModel myModel;
    tableView.setModel(&myModel);
    tableView.show();
    return a.exec();
}

// mymodel.h
#include <QAbstractTableModel>

class MyModel : public QAbstractTableModel
{
    Q_OBJECT
public:
    explicit MyModel(QObject *parent = nullptr);

    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
    int columnCount(const QModelIndex &parent = QModelIndex()) const override;
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
};

// mymodel.cpp
#include "mymodel.h"

MyModel::MyModel(QObject *parent)
    : QAbstractTableModel(parent)
{
}

int MyModel::rowCount(const QModelIndex & /*parent*/) const
{
   return 2;
}

int MyModel::columnCount(const QModelIndex & /*parent*/) const
{
    return 3;
}

QVariant MyModel::data(const QModelIndex &index, int role) const
{
    if (role == Qt::DisplayRole)
       return QString("Row%1, Column%2")
                   .arg(index.row() + 1)
                   .arg(index.column() +1);

    return QVariant();
}

// mymodel.cpp
QVariant MyModel::data(const QModelIndex &index, int role) const
{
    int row = index.row();
    int col = index.column();
    // generate a log message when this method gets called
    qDebug() << QString("row %1, col%2, role %3")
            .arg(row).arg(col).arg(role);

    switch (role) {
    case Qt::DisplayRole:
        if (row == 0 && col == 1) return QString("<--left");
        if (row == 1 && col == 1) return QString("right-->");

        return QString("Row%1, Column%2")
                .arg(row + 1)
                .arg(col +1);
    case Qt::FontRole:
        if (row == 0 && col == 0) { // change font only for cell(0,0)
            QFont boldFont;
            boldFont.setBold(true);
            return boldFont;
        }
        break;
    case Qt::BackgroundRole:
        if (row == 1 && col == 2)  // change background only for cell(1,2)
            return QBrush(Qt::red);
        break;
    case Qt::TextAlignmentRole:
        if (row == 1 && col == 1) // change text alignment only for cell(1,1)
            return int(Qt::AlignRight | Qt::AlignVCenter);
        break;
    case Qt::CheckStateRole:
        if (row == 1 && col == 0) // add a checkbox to cell(1,0)
            return Qt::Checked;
        break;
    }
    return QVariant();
}

QVariant MyModel::data(const QModelIndex &index, int role) const
{
    int row = index.row();
    int col = index.column();

    if (role == Qt::DisplayRole && row == 0 && col == 0)
        return QTime::currentTime().toString();

    return QVariant();
}

MyModel::MyModel(QObject *parent)
    : QAbstractTableModel(parent)
    , timer(new QTimer(this))
{
    timer->setInterval(1000);
    connect(timer, &QTimer::timeout , this, &MyModel::timerHit);
    timer->start();
}

void MyModel::timerHit()
{
    // we identify the top left cell
    QModelIndex topLeft = createIndex(0,0);
    // emit a signal to make the view reread identified data
    emit dataChanged(topLeft, topLeft, {Qt::DisplayRole});
}

QVariant MyModel::headerData(int section, Qt::Orientation orientation, int role) const
{
    if (role == Qt::DisplayRole && orientation == Qt::Horizontal) {
        switch (section) {
        case 0:
            return QString("first");
        case 1:
            return QString("second");
        case 2:
            return QString("third");
        }
    }
    return QVariant();
}

// mymodel.h
#include <QAbstractTableModel>
#include <QString>

const int COLS= 3;
const int ROWS= 2;

class MyModel : public QAbstractTableModel
{
    Q_OBJECT
public:
    MyModel(QObject *parent = nullptr);
    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
    int columnCount(const QModelIndex &parent = QModelIndex()) const override;
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
    bool setData(const QModelIndex &index, const QVariant &value, int role = Qt::EditRole) override;
    Qt::ItemFlags flags(const QModelIndex &index) const override;
private:
    QString m_gridData[ROWS][COLS];  //holds text entered into QTableView
signals:
    void editCompleted(const QString &);
};

bool MyModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    if (role == Qt::EditRole) {
        if (!checkIndex(index))
            return false;
        //save value from editor to member m_gridData
        m_gridData[index.row()][index.column()] = value.toString();
        //for presentation purposes only: build and emit a joined string
        QString result;
        for (int row = 0; row < ROWS; row++) {
            for (int col= 0; col < COLS; col++)
                result += m_gridData[row][col] + ' ';
        }
        emit editCompleted(result);
        return true;
    }
    return false;
}

Qt::ItemFlags MyModel::flags(const QModelIndex &index) const
{
    return Qt::ItemIsEditable | QAbstractTableModel::flags(index);
}

// modelview.cpp
#include "mainwindow.h"

#include <QTreeView>
#include <QStandardItemModel>
#include <QStandardItem>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , treeView(new QTreeView(this))
    , standardModel(new QStandardItemModel(this))
{
    setCentralWidget(treeView);

    QList<QStandardItem *> preparedRow = prepareRow("first", "second", "third");
    QStandardItem *item = standardModel->invisibleRootItem();
    // adding a row to the invisible root item produces a root element
    item->appendRow(preparedRow);

    QList<QStandardItem *> secondRow = prepareRow("111", "222", "333");
    // adding a row to an item starts a subtree
    preparedRow.first()->appendRow(secondRow);

    treeView->setModel(standardModel);
    treeView->expandAll();
}

QList<QStandardItem *> MainWindow::prepareRow(const QString &first,
                                              const QString &second,
                                              const QString &third) const
{
    return {new QStandardItem(first),
            new QStandardItem(second),
            new QStandardItem(third)};
}

#include "mainwindow.h"

#include <QTreeView>
#include <QStandardItemModel>
#include <QItemSelectionModel>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , treeView(new QTreeView(this))
    , standardModel(new QStandardItemModel(this))
{
    setCentralWidget(treeView);
    auto *rootNode = standardModel->invisibleRootItem();

    // defining a couple of items
    auto *americaItem = new QStandardItem("America");
    auto *mexicoItem =  new QStandardItem("Canada");
    auto *usaItem =     new QStandardItem("USA");
    auto *bostonItem =  new QStandardItem("Boston");
    auto *europeItem =  new QStandardItem("Europe");
    auto *italyItem =   new QStandardItem("Italy");
    auto *romeItem =    new QStandardItem("Rome");
    auto *veronaItem =  new QStandardItem("Verona");

    // building up the hierarchy
    rootNode->    appendRow(americaItem);
    rootNode->    appendRow(europeItem);
    americaItem-> appendRow(mexicoItem);
    americaItem-> appendRow(usaItem);
    usaItem->     appendRow(bostonItem);
    europeItem->  appendRow(italyItem);
    italyItem->   appendRow(romeItem);
    italyItem->   appendRow(veronaItem);

    // register the model
    treeView->setModel(standardModel);
    treeView->expandAll();

    // selection changes shall trigger a slot
    QItemSelectionModel *selectionModel = treeView->selectionModel();
    connect(selectionModel, &QItemSelectionModel::selectionChanged,
            this, &MainWindow::selectionChangedSlot);
}

void MainWindow::selectionChangedSlot(const QItemSelection & /*newSelection*/, const QItemSelection & /*oldSelection*/)
{
    // get the text of the selected item
    const QModelIndex index = treeView->selectionModel()->currentIndex();
    QString selectedText = index.data(Qt::DisplayRole).toString();
    // find out the hierarchy level of the selected item
    int hierarchyLevel = 1;
    QModelIndex seekRoot = index;
    while (seekRoot.parent().isValid()) {
        seekRoot = seekRoot.parent();
        hierarchyLevel++;
    }
    QString showString = QString("%1, Level %2").arg(selectedText)
                         .arg(hierarchyLevel);
    setWindowTitle(showString);
}

class StarDelegate : public QStyledItemDelegate
{
    Q_OBJECT
public:
    StarDelegate(QWidget *parent = nullptr);
    void paint(QPainter *painter, const QStyleOptionViewItem &option,
               const QModelIndex &index) const;
    QSize sizeHint(const QStyleOptionViewItem &option,
                   const QModelIndex &index) const;
};