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。

bool SpreadSheet::readFile(const QString &filePath){QFile file(filePath);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_5_3);quint64 magic;in >> magic;if (SpreadSheet::MagicNumber != magic) {QMessageBox::warning(this, tr("Spreadsheet"),tr("The file is not a Spreadsheet file."));return false;}clear();quint32 row;quint32 column;QString str;QProgressDialog* process =progressDialog(this, tr("Load %1").arg(file.fileName()), SpreadSheet::mMaxRow);process->setModal(true);QApplication::setOverrideCursor(Qt::WaitCursor);while ( !in.atEnd()) {in >> row >> column >> str;setFormula(row, column, str);process->setValue(row);if ( process->wasCanceled()) {clear();delete process;file.close();}}QApplication::restoreOverrideCursor();delete process;return true;
}

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。

bool SpreadSheet::writeFile(const QString &filePath){QFile file(filePath);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);out.setVersion(QDataStream::Qt_5_3);out << (quint64) SpreadSheet::MagicNumber;QProgressDialog* progress =progressDialog(this, tr("Save %1").arg(file.fileName()), SpreadSheet::mMaxRow);progress->setModal(true);QApplication::setOverrideCursor(Qt::WaitCursor);QString str;for (int i(0); i != SpreadSheet::mMaxRow; ++i) {progress->setValue(i);qApp->processEvents(QEventLoop::ExcludeUserInputEvents);if ( progress->wasCanceled()) {file.remove();delete progress;return false;}for (int j(0); j != SpreadSheet::mMaxColumn; ++j) {str = formula(i, j);if ( !str.isEmpty()) {out << (quint32)i << (quint32)j << str;}}}delete progress;QApplication::restoreOverrideCursor();return true;
}

使用到的函数：

QProgressDialog* SpreadSheet::progressDialog(QWidget* widget, const QString &str, const int range){QProgressDialog* progressDialog(new QProgressDialog(widget));progressDialog->setLabelText(str);progressDialog->setRange(0, range);return progressDialog;
}