Qt4之利用QDataStream對文件進行存取

QDataStream提拱了一個二進制的數據流，並且與程序運行的操作系統平台無關。利用QDataStream類可以方便地保存和讀取各類數據。例如，在實現應用中常需要保存用戶設置的參數，以便下次運行時烣復關閉時的參數設置，可需要與其他程序交互參數等。

pararw.h:

1. #ifndef PARARW_H
2. #define PARARW_H
4. #include <QDialog>
6. class QLabel;
7. class QPushButton;
8. class QLineEdit;
9. class QComboBox;
10. class QSpinBox;
12. class ParaRW : public QDialog
13. {
14. Q_OBJECT
15. public:
16. ParaRW();
18. QLabel *label1;
19. QLabel *label2;
20. QLabel *label3;
21. QLabel *label4;
22. QLabel *label5;
23. QLabel *timeLabel;
24. QPushButton *saveButton;
25. QPushButton *getButton;
26. QComboBox *powerComboBox;
27. QSpinBox *channelSpinBox;
28. QLineEdit *frequencyEdit;
30. public slots:
31. void slotSave();
32. void slotGet();
34. };
36. #endif // PARARW_H

pararw.cpp:

1. #include "pararw.h"
2. #include <QtGui>
4. ParaRW::ParaRW()
5. {
6. QFont f("ZYSong18030",12);
7. setFont(f);
9. setWindowTitle(tr("QDataStrem"));
11. label1 = new QLabel(tr("Channel:"));
12. label2 = new QLabel(tr("Power:"));
13. label3 = new QLabel(tr("Frequency:"));
14. label4 = new QLabel(tr("MHz"));
15. label5 = new QLabel(tr("Last save time:"));
16. timeLabel = new QLabel;
18. saveButton = new QPushButton(tr("Save"));
19. getButton = new QPushButton(tr("Get"));
21. channelSpinBox = new QSpinBox;
22. channelSpinBox->setRange(0,10);
23. powerComboBox = new QComboBox;
24. powerComboBox->insertItem(0,tr("small"));
25. powerComboBox->insertItem(1,tr("mid"));
26. powerComboBox->insertItem(2,tr("big"));
27. frequencyEdit = new QLineEdit;
29. QGridLayout *layout = new QGridLayout(this);
30. layout->setMargin(20);
31. layout->setSpacing(10);
32. layout->addWidget(label1,0,0);
33. layout->addWidget(channelSpinBox,0,1);
34. layout->addWidget(label2,1,0);
35. layout->addWidget(powerComboBox,1,1);
36. layout->addWidget(label3,2,0);
37. layout->addWidget(frequencyEdit,2,1);
38. layout->addWidget(label4,2,2);
39. layout->addWidget(label5,0,2);
40. layout->addWidget(timeLabel,0,3);
41. layout->addWidget(saveButton,1,3);
42. layout->addWidget(getButton,2,3);
44. connect(saveButton,SIGNAL(clicked()),this,SLOT(slotSave()));
45. connect(getButton,SIGNAL(clicked()),this,SLOT(slotGet()));
46. }
48. void
49. ParaRW::slotSave()
50. {
51. int channel = channelSpinBox->value();
52. int power = powerComboBox->currentIndex();
53. float frequency = frequencyEdit->text().toFloat();
54. QDateTime *time = new QDateTime;
56. QFile file("parameters.dat");
57. file.open(QIODevice::WriteOnly);
58. QDataStream out(&file);
60. out.setVersion(QDataStream::Qt_4_0);
61. out << (quint32)0xa1a2a3a4;
63. out << (qint32)channel << (qint32)power << frequency << time->currentDateTime();
64. }
66. void
67. ParaRW::slotGet()
68. {
69. QFile file("parameters.dat");
70. file.open(QIODevice::ReadOnly);
71. QDataStream in(&file);
73. in.setVersion(QDataStream::Qt_4_0);
74. qint32 magic;
75. in >> magic;
76. if (magic != 0xa1a2a3a4)
77. {
78. QMessageBox::information(this,"exception",tr("invalide file format"));
79. return;
80. }
82. qint32 channel;
83. qint32 power;
84. float frequency;
85. QDateTime time;
86. in >> channel >> power >> frequency >> time;
88. channelSpinBox->setValue(channel);
89. powerComboBox->setCurrentIndex(power);
90. QString freq;
91. frequencyEdit->setText(freq.setNum(frequency));
92. QString lastTime = time.date().toString(Qt::ISODate) + " " + time.time().toString();
93. timeLabel->setText(lastTime);
94. }