QT 新建、打开、保存文件

参考博客：https://blog.csdn.net/WQ_1996/article/details/78237151

环境：Qt5.8 win7

一、创建一个名为“file_operate”的项目文件

生成file_operate.pro、mainwindow.h、mainwindow.cpp、main.cpp、mainwindow.ui五个文件。

二、打开mainwindow.ui

1.添加“文件”菜单，并添加“new_file”、“open_file”、“save_file”、“save_as_file”四个Action。

2.向窗口中拖入“Text Edit”控件。并在属性编辑的“geometry“X、Y、宽度、高度分别设置为150,100,500,600。

3.添加槽函数

在ui设计界面下方的“Action Editor”中，选中动作“new_file"，右键选择“转到槽...”，选择"triggered()"，进入槽函数编辑模式。

以此类推，添加open_file，save_file，save_as_file槽函数。

三、.进入编辑模式（代码转载自https://blog.csdn.net/WQ_1996/article/details/78237151）

1. mainwindow.h代码如下：

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_new_file_triggered();
    void on_open_file_triggered();
    void on_save_as_file_triggered();
    void on_save_file_triggered();
    void on_closeEvent(QCloseEvent *event);

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

2.mainwindow.cpp代码如下：

/*
class QFileDialog
//QFileDialog类继承自QDialog类。QFileDialog类为用户提供了选择文件/路径的对话框。

class QFileDevice
//QFileDevice类继承自QFileDevice类，派生类有QFile、QSaveFile。QFileDevice类提供了用于读写打开文件的接口。

class QFile
//QFile类继承自QFileDevice类，派生类有QTemporaryFile。QFile类提供了用于读写文件的接口。

class QTextStream
//QTextStream类提供了方便的读写文本的界面。
*/

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QFileDialog>
#include <QFileDevice>
#include <QFile>
#include <QMessageBox>
#include <QtEvents>
#include <QTextStream>

int flag_isOpen = 0;
int flag_isNew = 0;
QString Last_FileName;
QString Last_FileContent;

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_open_file_triggered()
{
    QString fileName;
    fileName = QFileDialog::getOpenFileName(this,"Open File","","Text File(*.txt)");
    if(fileName == "")
    {
        return ;
    }
    else
    {
        QFile file(fileName);
        if(!file.open(QIODevice::ReadOnly | QIODevice::Text))
        {
            QMessageBox::warning(this,"error","open file error!");
            return;
        }
        else
        {
            if(!file.isReadable())
                QMessageBox::warning(this,"error","this file is not readable!");
            else
            {
                QTextStream textStream(&file);
                while(!textStream.atEnd())
                {
                    ui->textEdit->setPlainText(textStream.readAll());
                }
                ui->textEdit->show();
                file.close();
                flag_isOpen = 1;
                Last_FileName = fileName;
            }
        }
    }
}

void MainWindow::on_new_file_triggered()
{
    ui->textEdit->clear();
    ui->textEdit->setHidden(false);
    flag_isNew = 1;
    flag_isOpen = 1;
}

void MainWindow::on_save_as_file_triggered()
{
    QFileDialog fileDialog;
    QString fileName = fileDialog.getSaveFileName(this,"Open File","","Text File(*.txt)");
    if(fileName == "")
    {
        return;
    }
    QFile file(fileName);
    if(!file.open(QIODevice::WriteOnly | QIODevice::Text))
    {
        QMessageBox::warning(this,"error","open file failure!");
        return;
    }
    else
    {
        QTextStream textStream(&file);
        QString str = ui->textEdit->toPlainText();
        textStream<<str;
        QMessageBox::warning(this,"tip","Save File Success!");
        Last_FileContent = str;
        Last_FileName = fileName;
        flag_isNew = 0;
        file.close();
    }
}

void MainWindow::on_save_file_triggered()
{
    if(flag_isNew)
    {
        if(ui->textEdit->toPlainText()=="")
        {
            QMessageBox::warning(this,"error","content can not be none!",QMessageBox::Ok);
        }
        else
        {
            QFileDialog fileDialog;
            QString str = fileDialog.getSaveFileName(this,"Open File","","Text File(*.txt)");
            if(str == "")
            {
                return;
            }
            QFile filename(str);
            if(!filename.open(QIODevice::WriteOnly | QIODevice::Text))
            {
                QMessageBox::warning(this,"error","Open File Error!");
                return;
            }
            else
            {
                QTextStream textStream(&filename);
                QString str = ui->textEdit->toPlainText();
                textStream << str;
                Last_FileContent =str;
            }
            QMessageBox::information(this,"Ssve File","Save File Success",QMessageBox::Ok);
            filename.close();
            flag_isNew = 0;
            Last_FileName = str;
        }
    }
    else
    {
        if(flag_isOpen)
        {
            QFile file(Last_FileName);
            if(!file.open(QIODevice::WriteOnly | QIODevice::Text))
            {
                QMessageBox::warning(this,"error","Open File Faile");
                return;
            }
            else
            {
                QTextStream textString(&file);
                QString str = ui->textEdit->toPlainText();
                textString << str;
                Last_FileContent = str;
                file.close();
            }
        }
        else
        {
            QMessageBox::warning(this,"Warning","Please new or open a file");
            return;
        }

    }
}

void MainWindow::on_closeEvent(QCloseEvent *event)
{
    if(ui->textEdit->toPlainText() == Last_FileContent)
        event->accept();
    else
    {
        if(QMessageBox::warning(this,"Warning","the file have not save,ensure exit?",QMessageBox::Yes|QMessageBox::No) == QMessageBox::Yes)
        {
            event->accept();
        }
        else
            event->ignore();
    }
}

3.mian.cpp内容不做更改

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

四、实验结果如下：

QT 新建、打开 、保存文件

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