Qt读写数据流文件（转 CppGuiProgrammingWithQt4）

读取文件：

update 20140525：添加线程处理，在读取大文件时优化，防止app出现application假死状态。

1bool SpreadSheet::readFile(const QString &filePath){
2    QFile file(filePath);
3
4    if ( !file.open(QIODevice::ReadOnly)) {
5        QMessageBox::warning(this, tr("Spreadsheet"),
6                             tr("Cannot read file %1:\n%2.")
7                             .arg(file.fileName())
8                             .arg(file.errorString()));
9
10        return false;
11    }
12
13    QDataStream in(&file);
14    in.setVersion(QDataStream::Qt_5_3);
15
16    quint64 magic;
17    in >> magic;
18
19    if (SpreadSheet::MagicNumber != magic) {
20        QMessageBox::warning(this, tr("Spreadsheet"),
21                             tr("The file is not a Spreadsheet file."));
22
23        return false;
24    }
25
26    clear();
27
28    quint32 row;
29    quint32 column;
30    QString str;
31
32    QProgressDialog* process =
33            progressDialog(this, tr("Load %1").arg(file.fileName()), SpreadSheet::mMaxRow);
34    process->setModal(true);
35
36    QApplication::setOverrideCursor(Qt::WaitCursor);
37
38    while ( !in.atEnd()) {
39        in >> row >> column >> str;
40        setFormula(row, column, str);
41
42        process->setValue(row);
43
44        if ( process->wasCanceled()) {
45            clear();
46            delete process;
47            file.close();
48        }
49    }
50
51    QApplication::restoreOverrideCursor();
52    delete process;
53
54    return true;
55}

写入文件：

update 20140525：添加线程处理，在写入大文件时优化，防止app出现application假死状态。

1bool SpreadSheet::writeFile(const QString &filePath){
2    QFile file(filePath);
3
4    if ( !file.open(QIODevice::WriteOnly)) {
5        QMessageBox::warning(this, tr("Spreadsheet"),
6                             tr("Cannot write file %1:\n%2.")
7                             .arg(file.fileName())
8                             .arg(file.errorString()));
9
10        return false;
11    }
12
13    QDataStream out(&file);
14    out.setVersion(QDataStream::Qt_5_3);
15
16    out << (quint64) SpreadSheet::MagicNumber;
17
18    QProgressDialog* progress =
19            progressDialog(this, tr("Save %1").arg(file.fileName()), SpreadSheet::mMaxRow);
20    progress->setModal(true);
21
22    QApplication::setOverrideCursor(Qt::WaitCursor);
23    QString str;
24
25    for (int i(0); i != SpreadSheet::mMaxRow; ++i) {
26        progress->setValue(i);
27        qApp->processEvents(QEventLoop::ExcludeUserInputEvents);
28
29        if ( progress->wasCanceled()) {
30            file.remove();
31            delete progress;
32            return false;
33        }
34
35        for (int j(0); j != SpreadSheet::mMaxColumn; ++j) {
36            str = formula(i, j);
37
38            if ( !str.isEmpty()) {
39                out << (quint32)i << (quint32)j << str;
40            }
41        }
42    }
43
44    delete progress;
45    QApplication::restoreOverrideCursor();
46
47    return true;
48}

使用到的函数：

1QProgressDialog* SpreadSheet::progressDialog(QWidget* widget, 
2                                             const QString &str, 
3                                             const int range){
4     QProgressDialog* progressDialog(new QProgressDialog(widget));
5     progressDialog->setLabelText(str);
6     progressDialog->setRange(0, range);
7
8     return progressDialog;
9}