一、文件普通读写和流式读写

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QTextEdit>
#include <QLineEdit>
#include <QPushButton>
#include <QFileDialog>
#include <QTextStream>

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
    ~Widget();
public slots:
    void showfile()
    {
        QString filename = QFileDialog::getOpenFileName();
        le->setText(filename);
#if 0
        //普通写法
        QFile file(filename);
        if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
             return;

        while (!file.atEnd()) {
             QByteArray line = file.readLine();
            // process_line(line);
             te->append(line);
        }
#endif
        //适配器写法用流来操作流支持输出运算符
        QFile file(filename);
              if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
                  return;

              QTextStream in(&file);
              while (!in.atEnd()) {
                  QString line = in.readLine();
                //  process_line(line);
                  te->append(line);
              }
    }

private:
    QTextEdit *te;
    QLineEdit *le;
    QPushButton *pb;
};

#endif // WIDGET_H

#include "widget.h"
#include <QVBoxLayout>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    te = new QTextEdit;
    te->setMinimumSize(640, 480);
    le = new QLineEdit;
    pb = new QPushButton("showtxt");

    QVBoxLayout *vbox = new QVBoxLayout;
    vbox->addWidget(te);
    vbox->addWidget(le);
    vbox->addWidget(pb);
    setLayout(vbox);

    connect(pb, SIGNAL(clicked(bool)), this, SLOT(showfile()));
}

Widget::~Widget()
{

}

用两种方式来读文件，都在代码里。最好的学习方式就是根据代码学

之前教我进程线程的老师是这样说的，我也很赞同这个观点，所以自己看代码吧

二、目录遍历和文件属性读写

新建一个控制台程序

只有一个主函数，没有GUI

运行起来也只是一个黑框框

我们写个程序来试试

#include <QCoreApplication>
#include <QDir>
#include <QFileInfo>
#include <iostream>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QDir dir;

    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 << fileInfo.size()<< "\t"<<fileInfo.fileName().toStdString().c_str();

         std::cout << std::endl;
    }

    return a.exec();
}

三、进程

选着文件打开后会自动开启一个进程用windows自带的文本阅读器打开选择的文件

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QLineEdit>
#include <QPushButton>
#include <QFileDialog>
#include <QProcess>
#include <QStringList>

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
    ~Widget();
public slots:
    void showfile()
    {
        QString filename = QFileDialog::getOpenFileName();
        le->setText(filename);

        QStringList arg = {filename};
        QProcess ppp;
        ppp.execute("notepad", arg);
    }

private:
    QLineEdit *le;
    QPushButton *pb;
};

#endif // WIDGET_H

#include "widget.h"
#include <QVBoxLayout>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    le = new QLineEdit;
    pb = new QPushButton("showtxt");

    QVBoxLayout *vbox = new QVBoxLayout;
    vbox->addWidget(le);
    vbox->addWidget(pb);
    setLayout(vbox);

    connect(pb, SIGNAL(clicked(bool)), this, SLOT(showfile()));
}

Widget::~Widget()
{

}