Qt常用类

向控制台输出文本

第一个例子，我们采用STL的方式：

#include <iostream>int main()
{std::cout << "console application\n";
}

第二个例子我们用QT4编程库

#include <QTextStream>int main()
{QTextStream out(stdout);out << "console application\n";
}

Output

console application

QFile

写一行字符串到文件中

#include <QTextStream>
#include <QFile>int main()
{QFile data("myfile");if (data.open(QFile::WriteOnly)) {QTextStream out(&data);out << "You make me want to be a better man." << endl;}
}

$ cat myfile
You make me want to be a better man.

下面的例子我们输出一段文本到控制台

S a régi szeretőmér­
mit nem cselekednék,
tengerből a vizet
kanállal lemerném.S a tenger fenekéről
apró gyöngyöt szednék,
s a régi szeretőmnek
gyöngykoszorút kötnék.

#include <QTextStream>
#include <QFile>int main()
{QFile data("szerelem");QString line;if (data.open(QFile::ReadOnly)) {QTextStream in(&data);QTextStream out(stdout);out.setCodec("UTF-8");in.setCodec("UTF-8");do {line = in.readLine();out << line << endl;} while (!line.isNull());}
}

 S a régi szeretőmér­
mit nem cselekednék,
tengerből a vizet
kanállal lemerném.S a tenger fenekéről
apró gyöngyöt szednék,
s a régi szeretőmnek
gyöngykoszorút kötnék.

QList

Qt容器类之一

#include <QTextStream>
#include <QList>int main()
{QTextStream out(stdout);QList<QString> list;list << "Balzac" << "Tolstoy" << "Guldbrassen"<< "London" << "Galsworthy" << "Sienkiewicz";qSort(list);for (int i = 0; i < list.size(); ++i) {out << list.at(i) << endl;}}

Output

Balzac
Galsworthy
Guldbrassen
London
Sienkiewicz
Tolstoy

QDir

管理文件目录

#include <QTextStream>
#include <QDir>int main()
{QTextStream out(stdout);QString home = QDir::homePath();out << home << endl;
}

Output

/home/vronskij

输出应用程序所在路径中扩展名是.c的全部文件名字

#include <QTextStream>
#include <QDir>int main()
{QTextStream out(stdout);QDir dir;QStringList filters;filters << "*.c" << "*.c~";dir.setNameFilters(filters);QFileInfoList list = dir.entryInfoList();for (int i = 0; i < list.size(); ++i) {QFileInfo fileInfo = list.at(i);out << QString("%1").arg(fileInfo.fileName());out << endl;}
}

$ ls -F
anim*  anim.c  anim.c~  filters*
$ ./filters
anim.c
anim.c~

QTime

输出当前时间

#include <QTextStream>
#include <QTime>int main()
{QTextStream out(stdout);QTime qtime = QTime::currentTime();QString stime = qtime.toString(Qt::LocalDate);out << stime << endl;
}

Output

$ ./time
10:30:33 PM

QString

字符串连接

#include <QTextStream>int main()
{QString a = "Disziplin ";QString b = "ist ";QString c = "Macht.\n";QTextStream out(stdout);out << a + b + c;
}

$ ./concat
Disziplin ist Macht.

字符串追加

#include <QTextStream>int main()
{QString string = "Whether I shall ";string.append("turn out to be the hero of my own life, \n");string.append("or whether that station will be held by anybody else, \n");string.append("these pages must show.\n");QTextStream out(stdout);out << string;
}

$ ./append
Whether I shall turn out to be the hero of my own life,
or whether that station will be held by anybody else,
these pages must show.

参数替换

#include <QTextStream>int main()
{QString string = "What if I gave you %1 red roses?";int num = 21;QTextStream out(stdout);out << string.arg(num) << endl;
}

$ ./str3
What if I gave you 21 red roses?

输出字符串长度

#include <QTextStream>int main()
{QString string = "The history of my life.";QTextStream out(stdout);out << "The string has " + QString::number(string.size())+ " characters." << endl;
}

 ./size
The string has 23 characters.

字符串大小写转换

#include <QTextStream>int main()
{QString string = "The history of my life.";QTextStream out(stdout);out << string.toLower() << endl; out << string.toUpper() << endl;
}

$ ./uplow
the history of my life.
THE HISTORY OF MY LIFE.