第四章 实现应用程序的功能

类Spreadsheet从QTableWidget派生而来，

spreadsheet.h

#ifndef SPREADSHEET_H
#define SPREADSHEET_H

#include <QTableWidget>
#include <QMessageBox>
#include <QString>
#include <QTableWidgetSelectionRange>

#include "cell.h"
class SpreadsheetCompare;

class Spreadsheet : public QTableWidget
{
    Q_OBJECT

public:
    Spreadsheet(QWidget *parent = 0);

    bool autoRecalculate() const { return autoRecalc; }
    QString currentLocation() const;
    QString currentFormula() const;
    QTableWidgetSelectionRange selectedRange() const;
    void clear();
    bool readFile(const QString &fileName);
    bool writeFile(const QString &fileName);
    void sort(const SpreadsheetCompare &compare);

public slots:
    void cut();
    void copy();
    void paste();
    void del();
    void selectCurrentRow();
    void selectCurrentColumn();
    void recalculate();
    void setAutoRecalculate(bool recalc);
    void findNext(const QString &str, Qt::CaseSensitivity cs);
    void findPrevious(const QString &str, Qt::CaseSensitivity cs);

signals:
    void modified();

private slots:
    void somethingChanged();

private:
    enum { MagicNumber = 0x7F51C883, RowCount = 999, ColumnCount = 26 };

    Cell *cell(int row, int column) const;
    QString text(int row, int column) const;
    QString formula(int row, int column) const;
    void setFormula(int row, int column, const QString &formula);

    bool autoRecalc;
};

class SpreadsheetCompare
{
public:
    bool operator()(const QStringList &row1,
                    const QStringList &row2) const;

    enum { KeyCount = 3 };
    int keys[KeyCount];
    bool ascending[KeyCount];
};

#endif

实现文件（不对他怎么实现的功能做太多解释，需要仔细研究代码才能理解Qt）

spreadsheet.cpp

#include <QtGui>
#include <QApplication>

#include "cell.h"
#include "spreadsheet.h"

Spreadsheet::Spreadsheet(QWidget *parent)
    : QTableWidget(parent)
{
    autoRecalc = true;

    setItemPrototype(new Cell);

	//可以允许简单矩形选择框方法
    setSelectionMode(ContiguousSelection);
    connect(this, SIGNAL(itemChanged(QTableWidgetItem *)), this, SLOT(somethingChanged()));

	//重新调整表格的尺寸大小并设置列标题
    clear();
}

QString Spreadsheet::currentLocation() const
{
    return QChar('A' + currentColumn()) + QString::number(currentRow() + 1);
}

QString Spreadsheet::currentFormula() const
{
    return formula(currentRow(), currentColumn());
}

QTableWidgetSelectionRange Spreadsheet::selectedRange() const
{
    QList<QTableWidgetSelectionRange> ranges = selectedRanges();
    if (ranges.isEmpty())
        return QTableWidgetSelectionRange();
    return ranges.first();
}

void Spreadsheet::clear()
{
    setRowCount(0);
    setColumnCount(0);
    setRowCount(RowCount);
    setColumnCount(ColumnCount);

    for (int i = 0; i < ColumnCount; ++i) 
	{
        QTableWidgetItem *item = new QTableWidgetItem;
        item->setText(QString(QChar('A' + i)));
        setHorizontalHeaderItem(i, item);
    }

    setCurrentCell(0, 0);
}

bool Spreadsheet::readFile(const QString &fileName)
{
    QFile file(fileName);
    if (!file.open(QIODevice::ReadOnly)) {
        QMessageBox::warning(this, tr("Spreadsheet"),
                             tr("Cannot read file %1:\n%2.")
                             .arg(file.fileName())
                             .arg(file.errorString()));
        return false;
    }

    QDataStream in(&file);
    in.setVersion(QDataStream::Qt_4_3);

    quint32 magic;
    in >> magic;
    if (magic != MagicNumber) {
        QMessageBox::warning(this, tr("Spreadsheet"),
                             tr("The file is not a Spreadsheet file."));
        return false;
    }

    clear();

    quint16 row;
    quint16 column;
    QString str;

    QApplication::setOverrideCursor(Qt::WaitCursor);
    while (!in.atEnd()) {
        in >> row >> column >> str;
        setFormula(row, column, str);
    }
    QApplication::restoreOverrideCursor();
    return true;
}

bool Spreadsheet::writeFile(const QString &fileName)
{
    QFile file(fileName);
    if (!file.open(QIODevice::WriteOnly)) {
        QMessageBox::warning(this, tr("Spreadsheet"),
                             tr("Cannot write file %1:\n%2.")
                             .arg(file.fileName())
                             .arg(file.errorString()));
        return false;
    }

    QDataStream out(&file);

	//避免出现因为版本不同出现问题，可以指定版本
    out.setVersion(QDataStream::Qt_4_3);

    out << quint32(MagicNumber);

    QApplication::setOverrideCursor(Qt::WaitCursor);
    for (int row = 0; row < RowCount; ++row) {
        for (int column = 0; column < ColumnCount; ++column) {
            QString str = formula(row, column);
            if (!str.isEmpty())
                out << quint16(row) << quint16(column) << str;
        }
    }
    QApplication::restoreOverrideCursor();
    return true;
}

void Spreadsheet::sort(const SpreadsheetCompare &compare)
{
    QList<QStringList> rows;
    QTableWidgetSelectionRange range = selectedRange();
    int i;

    for (i = 0; i < range.rowCount(); ++i) {
        QStringList row;
        for (int j = 0; j < range.columnCount(); ++j)
            row.append(formula(range.topRow() + i,
                               range.leftColumn() + j));
        rows.append(row);
    }

    qStableSort(rows.begin(), rows.end(), compare);

    for (i = 0; i < range.rowCount(); ++i) {
        for (int j = 0; j < range.columnCount(); ++j)
            setFormula(range.topRow() + i, range.leftColumn() + j,
                       rows[i][j]);
    }

    clearSelection();
    somethingChanged();
}

void Spreadsheet::cut()
{
    copy();
    del();
}

void Spreadsheet::copy()
{
    QTableWidgetSelectionRange range = selectedRange();
    QString str;

    for (int i = 0; i < range.rowCount(); ++i) {
        if (i > 0)
            str += "\n";
        for (int j = 0; j < range.columnCount(); ++j) {
            if (j > 0)
                str += "\t";
            str += formula(range.topRow() + i, range.leftColumn() + j);
        }
    }
    QApplication::clipboard()->setText(str);
}

void Spreadsheet::paste()
{
    QTableWidgetSelectionRange range = selectedRange();
    QString str = QApplication::clipboard()->text();
    QStringList rows = str.split('\n');
    int numRows = rows.count();
    int numColumns = rows.first().count('\t') + 1;

    if (range.rowCount() * range.columnCount() != 1
            && (range.rowCount() != numRows
                || range.columnCount() != numColumns)) {
        QMessageBox::information(this, tr("Spreadsheet"),
                tr("The information cannot be pasted because the copy "
                   "and paste areas aren't the same size."));
        return;
    }

    for (int i = 0; i < numRows; ++i) {
        QStringList columns = rows[i].split('\t');
        for (int j = 0; j < numColumns; ++j) {
            int row = range.topRow() + i;
            int column = range.leftColumn() + j;
            if (row < RowCount && column < ColumnCount)
                setFormula(row, column, columns[j]);
        }
    }
    somethingChanged();
}

void Spreadsheet::del()
{
    QList<QTableWidgetItem *> items = selectedItems();
    if (!items.isEmpty()) {
        foreach (QTableWidgetItem *item, items)
            delete item;
        somethingChanged();
    }
}

void Spreadsheet::selectCurrentRow()
{
    selectRow(currentRow());
}

void Spreadsheet::selectCurrentColumn()
{
    selectColumn(currentColumn());
}

void Spreadsheet::recalculate()
{
    for (int row = 0; row < RowCount; ++row) {
        for (int column = 0; column < ColumnCount; ++column) {
            if (cell(row, column))
                cell(row, column)->setDirty();
        }
    }
    viewport()->update();
}

void Spreadsheet::setAutoRecalculate(bool recalc)
{
    autoRecalc = recalc;
    if (autoRecalc)
        recalculate();
}

void Spreadsheet::findNext(const QString &str, Qt::CaseSensitivity cs)
{
    int row = currentRow();
    int column = currentColumn() + 1;

    while (row < RowCount) {
        while (column < ColumnCount) {
            if (text(row, column).contains(str, cs)) {
                clearSelection();
                setCurrentCell(row, column);
                activateWindow();
                return;
            }
            ++column;
        }
        column = 0;
        ++row;
    }
    QApplication::beep();
}

void Spreadsheet::findPrevious(const QString &str,
                               Qt::CaseSensitivity cs)
{
    int row = currentRow();
    int column = currentColumn() - 1;

    while (row >= 0) {
        while (column >= 0) {
            if (text(row, column).contains(str, cs)) {
                clearSelection();
                setCurrentCell(row, column);
                activateWindow();
                return;
            }
            --column;
        }
        column = ColumnCount - 1;
        --row;
    }
    QApplication::beep();
}

void Spreadsheet::somethingChanged()
{
    if (autoRecalc)
        recalculate();
    emit modified();
}

Cell *Spreadsheet::cell(int row, int column) const
{
	//给定行列，返回这个单元格
    return static_cast<Cell *>(item(row, column));
}

void Spreadsheet::setFormula(int row, int column,
                             const QString &formula)
{
    Cell *c = cell(row, column);
    if (!c) {
        c = new Cell;
        setItem(row, column, c);
    }
    c->setFormula(formula);
}

QString Spreadsheet::formula(int row, int column) const
{
    Cell *c = cell(row, column);
    if (c) {
        return c->formula();
    } else {
        return "";
    }
}

QString Spreadsheet::text(int row, int column) const
{
	//返回这个单元格的文本
	Cell *c = cell(row, column);
    if (c) {
        return c->text();
    } else {
        return "";
    }
}

bool SpreadsheetCompare::operator()(const QStringList &row1,
                                    const QStringList &row2) const
{
    for (int i = 0; i < KeyCount; ++i) {
        int column = keys[i];
        if (column != -1) {
            if (row1[column] != row2[column]) {
                if (ascending[i]) {
                    return row1[column] < row2[column];
                } else {
                    return row1[column] > row2[column];
                }
            }
        }
    }
    return false;
}

Cell类派生子QTbleWidgetItem. 这实际上是一个数据类，

"cell.h"

#ifndef CELL_H
#define CELL_H

#include <QTableWidgetItem>

class Cell : public QTableWidgetItem
{
public:
    Cell();

    QTableWidgetItem *clone() const;
    void setData(int role, const QVariant &value);
    QVariant data(int role) const;
    void setFormula(const QString &formula);
    QString formula() const;
    void setDirty();

private:
    QVariant value() const;
    QVariant evalExpression(const QString &str, int &pos) const;
    QVariant evalTerm(const QString &str, int &pos) const;
    QVariant evalFactor(const QString &str, int &pos) const;

    mutable QVariant cachedValue;
    mutable bool cacheIsDirty;
};

#endif

这个类的头文件并不包含 Q_OBJECT宏，因为只是一个普通的C++类，不是从QObject派生而来，所以就不让它有信号槽

cell.cpp

#include <QtGui>

#include "cell.h"

Cell::Cell()
{
    setDirty();
}

QTableWidgetItem *Cell::clone() const
{
    return new Cell(*this);
}

void Cell::setData(int role, const QVariant &value)
{
    QTableWidgetItem::setData(role, value);
    if (role == Qt::EditRole)
        setDirty();
}

QVariant Cell::data(int role) const
{
    if (role == Qt::DisplayRole) {
        if (value().isValid()) {
            return value().toString();
        } else {
            return "####";
        }
    } else if (role == Qt::TextAlignmentRole) {
        if (value().type() == QVariant::String) {
            return int(Qt::AlignLeft | Qt::AlignVCenter);
        } else {
            return int(Qt::AlignRight | Qt::AlignVCenter);
        }
    } else {
        return QTableWidgetItem::data(role);
    }
}

void Cell::setFormula(const QString &formula)
{
    setData(Qt::EditRole, formula);
}

QString Cell::formula() const
{
    return data(Qt::EditRole).toString();
}

void Cell::setDirty()
{
    cacheIsDirty = true;
}

const QVariant Invalid;

QVariant Cell::value() const
{
    if (cacheIsDirty) {
        cacheIsDirty = false;

        QString formulaStr = formula();
        if (formulaStr.startsWith('\'')) {
            cachedValue = formulaStr.mid(1);
        } else if (formulaStr.startsWith('=')) {
            cachedValue = Invalid;
            QString expr = formulaStr.mid(1);
            expr.replace(" ", "");
            expr.append(QChar::Null);

            int pos = 0;
            cachedValue = evalExpression(expr, pos);
            if (expr[pos] != QChar::Null)
                cachedValue = Invalid;
        } else {
            bool ok;
            double d = formulaStr.toDouble(&ok);
            if (ok) {
                cachedValue = d;
            } else {
                cachedValue = formulaStr;
            }
        }
    }
    return cachedValue;
}

QVariant Cell::evalExpression(const QString &str, int &pos) const
{
    QVariant result = evalTerm(str, pos);
    while (str[pos] != QChar::Null) {
        QChar op = str[pos];
        if (op != '+' && op != '-')
            return result;
        ++pos;

        QVariant term = evalTerm(str, pos);
        if (result.type() == QVariant::Double
                && term.type() == QVariant::Double) {
            if (op == '+') {
                result = result.toDouble() + term.toDouble();
            } else {
                result = result.toDouble() - term.toDouble();
            }
        } else {
            result = Invalid;
        }
    }
    return result;
}

QVariant Cell::evalTerm(const QString &str, int &pos) const
{
    QVariant result = evalFactor(str, pos);
    while (str[pos] != QChar::Null) {
        QChar op = str[pos];
        if (op != '*' && op != '/')
            return result;
        ++pos;

        QVariant factor = evalFactor(str, pos);
        if (result.type() == QVariant::Double
                && factor.type() == QVariant::Double) {
            if (op == '*') {
                result = result.toDouble() * factor.toDouble();
            } else {
                if (factor.toDouble() == 0.0) {
                    result = Invalid;
                } else {
                    result = result.toDouble() / factor.toDouble();
                }
            }
        } else {
            result = Invalid;
        }
    }
    return result;
}

QVariant Cell::evalFactor(const QString &str, int &pos) const
{
    QVariant result;
    bool negative = false;

    if (str[pos] == '-') {
        negative = true;
        ++pos;
    }

    if (str[pos] == '(') {
        ++pos;
        result = evalExpression(str, pos);
        if (str[pos] != ')')
            result = Invalid;
        ++pos;
    } else {
        QRegExp regExp("[A-Za-z][1-9][0-9]{0,2}");
        QString token;

        while (str[pos].isLetterOrNumber() || str[pos] == '.') {
            token += str[pos];
            ++pos;
        }

        if (regExp.exactMatch(token)) {
            int column = token[0].toUpper().unicode() - 'A';
            int row = token.mid(1).toInt() - 1;

            Cell *c = static_cast<Cell *>(
                              tableWidget()->item(row, column));
            if (c) {
                result = c->value();
            } else {
                result = 0.0;
            }
        } else {
            bool ok;
            result = token.toDouble(&ok);
            if (!ok)
                result = Invalid;
        }
    }

    if (negative) {
        if (result.type() == QVariant::Double) {
            result = -result.toDouble();
        } else {
            result = Invalid;
        }
    }
    return result;
}

文件结构：

补充整个工程（未粘贴出来的部分这里都有）：点击打开链接

（有什么问题可以联系我）

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