Qt学习笔记--访问磁盘文件

QFileInfo
获取文件信息：文件名称，路径，大小，创建时间，修改时间，权限等
使用
路径：
UNIX: /home/dipper/file1
Windows: C://dipper//file1

构造函数：
QFileInfo fileInfo(path);
QFileInfo fileInfo;
fileInfo.setFile(path);

exists(): 判断文件是否存在
size(): 获取文件大小

文件类型：
isFile(), isDir(), isSymLink()

symLinkTarget(): 返回符号链接的文件

注意：
UNIX和Windows（快捷方式）对符号链接处理不一样
UNIX: size()返回链接的目标文件的大小
Windows: size()返回链接文件本身的大小

#ifdef Q_OS_UNIX

QFileInfo info1("/home/bob/bin/untabify");
info1.isSymLink();          // returns true
info1.absoluteFilePath();   // returns "/home/bob/bin/untabify"
info1.size();               // returns 56201
info1.symLinkTarget();      // returns "/opt/pretty++/bin/untabify"

QFileInfo info2(info1.symLinkTarget());
info1.isSymLink();          // returns false
info1.absoluteFilePath();   // returns "/opt/pretty++/bin/untabify"
info1.size();               // returns 56201

#endif

#ifdef Q_OS_WIN

QFileInfo info1("C://Documents and Settings//Bob//untabify.lnk");
info1.isSymLink();          // returns true
info1.absoluteFilePath();   // returns "C:/Documents and Settings/Bob/untabify.lnk"
info1.size();               // returns 743
info1.symLinkTarget();      // returns "C:/Pretty++/untabify"

QFileInfo info2(info1.symLinkTarget());
info1.isSymLink();          // returns false
info1.absoluteFilePath();   // returns "C:/Pretty++/untabify"
info1.size();               // returns 63942

#endif

path(): 返回文件路径
fileName(): 返回文件名称

QFileInfo fileInfo("/home/dipper/xyz.tar.gz");
fileInfo.path(); // returns "/home/dipper"
fileInfo.fileName(); // returns "xyz.tar.gz"
fileInfo.baseName(); // returns "xyz"
fileInfo.completeBaseName(); // returns "xyz.tar"
fileInfo.suffix();   // returns "gz"
fileInfo.completeSuffix(); // returns "tar.gz"

日期相关：
created(): 创建时间
lastModified(): 最近修改时间
lastRead(): 最近读时间

权限：
isReadable(), isWritable(), isExecutable()

所有者：
ower(), owerId(), group(), groupId(), permissions(),
permission(QFile::Permissions permissions)

dir():  返回父目录
下面三个都返回"~/examples/191697"
QFileInfo fileInfo1("~/examples/191697/.");
QFileInfo fileInfo2("~/examples/191697/..");
QFileInfo fileInfo3("~/examples/191697/main.cpp");

下面三个都返回"."
QFileInfo fileInfo4(".");
QFileInfo fileInfo5("..");
QFileInfo fileInfo6("main.cpp");

相对路径和绝对路径
QString absolute = "/local/bin";
QString relative = "local/bin";
QFileInfo absFile(absolute);
QFileInfo relFile(relative);

QDir::setCurrent(QDir::rootPath());
// absFile and relFile now point to the same file

QDir::setCurrent("/tmp");
// absFile now points to "/local/bin",
// while relFile points to "/tmp/local/bin"

QDir 显示文件系统目录

实例：文件浏览器

//fileviewer.h
#ifndef FILEVIEWER_H
#define FILEVIEWER_H

#include <QtGui>

class FileViewer : public QDialog        // file information dialogs widget
{
Q_OBJECT
public:
FileViewer(QWidget *parent=0);
~FileViewer();
public:
QLineEdit* currDir;
QListWidget* fileListWidget;

public:
void showFileInfoList(QFileInfoList list);

public slots:
void showDir(QListWidgetItem * item);
void showFiles(QDir dir);
void showFiles();
};

#endif // FILEVIEWER_H

//fileviewer.cpp
#include "fileviewer.h"

FileViewer::FileViewer(QWidget *parent)
: QDialog(parent)
{ 
setWindowTitle(tr("File Viewer"));

currDir = new QLineEdit;
currDir->setText("c://");
//currDir->setReadOnly(true);

fileListWidget = new QListWidget;

QVBoxLayout *vbLayout = new QVBoxLayout(this);
vbLayout->addWidget(currDir);
vbLayout->addWidget(fileListWidget);

connect(currDir, SIGNAL(returnPressed()),
this, SLOT(showFiles()));

connect(fileListWidget, SIGNAL(itemDoubleClicked(QListWidgetItem *)),
this, SLOT(showDir(QListWidgetItem *)));

QString root = "c://";
QDir rootDir(root);

QStringList strings;
strings << "*" ;
QFileInfoList list = rootDir.entryInfoList(strings);
showFileInfoList(list);
}

FileViewer::~FileViewer()
{

}

//显示文件信息列表
void FileViewer::showFileInfoList(QFileInfoList list)
{
fileListWidget->clear();
for(int i=0; i<list.count(); i++)
{
QFileInfo tmpFileInfo = list.at(i);
if((tmpFileInfo.isDir()))
{
QIcon icon(":/images/dir.png");
QString fileName = tmpFileInfo.fileName();
QListWidgetItem *tmp = new QListWidgetItem(icon, fileName); //在列表上显示图标和名称
fileListWidget->addItem(tmp);
}
else if(tmpFileInfo.isFile())
{
QIcon icon(":/images/file.png");
QString fileName = tmpFileInfo.fileName();
QListWidgetItem *tmp = new QListWidgetItem (icon, fileName);
fileListWidget->addItem(tmp);
}
}
}

void FileViewer::showDir(QListWidgetItem * item)
{
QString str = item->text();
QDir dir;
dir.setPath(currDir->text()); //设置目录
dir.cd(str); //切换到另一个目录
currDir->setText(dir.absolutePath());
showFiles(dir);
}

void FileViewer::showFiles(QDir dir)
{
QStringList strings;
strings << "*" ;
QFileInfoList list = dir.entryInfoList(strings,   //文件名称过滤器，"*", "*.tar.gz"
QDir::AllEntries,  //文件属性过滤器，目录，文件，读写
QDir::DirsFirst  //排序方式，名称，修改时间，大小，目录优先
);
showFileInfoList(list);
}

void FileViewer::showFiles()
{
QDir dir(currDir->text());
showFiles(dir);
}

//main.cpp
#include "fileviewer.h"
#include <QApplication>

int main( int argc, char **argv )
{
QFont font("ZYSong18030",12);
QApplication::setFont(font);

QApplication app(argc, argv);
QTranslator translator;
translator.load("fileviewer_zh","..");
app.installTranslator(&translator);

FileViewer *fileviewer = new FileViewer;
fileviewer->show();
return app.exec();
}

绝对路径
QDir("/home/user/Documents")
QDir("C:/Documents and Settings")

dirName(): 返回目录名称
QDir("Documents/Letters/Applications").dirName() // "Applications"
QDir().dirName()                                 // "."

切换目录：cd(str), cdUp()

创建，修改，删除：mkdir(), rename(), rmdir()

获取目录里面的文件，目录等
count(): 返回条目的数量
QStringList list = dir.entryList();
QFileInfoList fileInfoList = dir.entryInfoList();

静态函数
Dir        Qstring
current(), currentPath()
home(),    homePath()
root(),    rootPath()
temp(),    tempPath()

QDir dir("example");
if (!dir.exists())
qWarning("Cannot find the example directory");
//使用静态函数：QFile::exists("example");

遍历目录，读写文件

QDir dir = QDir::root();                 // "/"
if (!dir.cd("tmp")) {                    // "/tmp"
qWarning("Cannot find the /"/tmp/" directory");
} else {
QFile file(dir.filePath("ex1.txt")); // "/tmp/ex1.txt"
if (!file.open(QIODevice::ReadWrite))
qWarning("Cannot create the file %s", file.name());
}

列出当前目录下所有文件，不包括符号链接，按大小排序，升序
#include <QDir>
#include <iostream>

int main(int argc, char *argv[])
{
QCoreApplication app(argc, argv);
QDir dir;
dir.setFilter(QDir::Files | QDir::Hidden | QDir::NoSymLinks);
dir.setSorting(QDir::Size | QDir::Reversed);

QFileInfoList list = dir.entryInfoList();
std::cout << "     Bytes Filename" << std::endl;
for (int i = 0; i < list.size(); ++i) {
QFileInfo fileInfo = list.at(i);
std::cout << qPrintable(QString("%1 %2").arg(fileInfo.size(), 10)
.arg(fileInfo.fileName()));
std::cout << std::endl;
}
return 0;
}