mainwindow.h

核心函数

• QFileDialog::getOpenFileName()
• QFileDialog::getSaveFileName()

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include<QFileDialog>
#include<QMessageBox>
#include<QDebug>
#include<QFile>
#include<QKeyEvent>
#include<QMouseEvent>

QT_BEGIN_NAMESPACE
namespace Ui {
class MainWindow;
}
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    void keyPressEvent(QKeyEvent *k);//父类虚函数，键盘按下事件
    void mousePressEvent(QMouseEvent *m);//鼠标按下事件
    ~MainWindow();

private:
    Ui::MainWindow *ui;
private slots:
    void newActionSlot();
    void openActionSlot();
    void saveActionSlot();
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    this->setWindowTitle("记事本");
    //连接函数，谁发出信息，发出什么信号，谁接收信号，执行什么操作
    //自定义三个槽函数，newActionSlot,openActionSlot,saveActionSlot
    connect(ui->newAction,&QAction::triggered,this,&MainWindow::newActionSlot);
    connect(ui->openAction,&QAction::triggered,this,&MainWindow::openActionSlot);
    connect(ui->saveAction,&QAction::triggered,this,&MainWindow::saveActionSlot);
}

MainWindow::~MainWindow()
{
    delete ui;
}
void MainWindow::newActionSlot()
{
//清空内容
    ui->textEdit->clear();
    this->setWindowTitle("新建文本文档.txt");
}
void MainWindow::openActionSlot()
{
//打开文件资源管理窗口，获取选定的文件的路径
    QString filename= QFileDialog::getOpenFileName(this, "打开文件",
                                 QCoreApplication::applicationFilePath(), "*.cpp");
    if(filename.isEmpty())
    {
        QMessageBox::warning(this,"警告","请打开一个文件！");
    }
    else{
        //qDebug() << filename;
        //通过文件路径，构建文件对象
        QFile file(filename);
        //只读方式打开
        file.open(QIODevice::ReadOnly);
        //读取文件中的所有内容到字节数组中
        QByteArray ba = file.readAll();
        //关闭文件对象
        file.close();
       	//将读取的数据存储到textEdit中
        ui->textEdit->setText(QString(ba));

    }
}
void MainWindow::saveActionSlot()
{
//弹出文件资源管理器窗口，选择文件夹。
//QCoreApplication::applicationFilePath()表示当前根目录
    QString filename=QFileDialog::getSaveFileName(this,"保存文件",
                                                    QCoreApplication::applicationFilePath());
    if(filename.isEmpty())
        QMessageBox::warning(this,"警告","请选择一个文件！");
    else
    {
        QFile file(filename);
        file.open(QIODevice::WriteOnly);
        QByteArray ba;
        ba.append(ui->textEdit->toPlainText().toUtf8());
        file.write(ba);
        file.close();
        QMessageBox::about(this,"提示","保存成功");
    }
}

void MainWindow::keyPressEvent(QKeyEvent *k)
{
//键盘按下事件，一个父类的虚函数，能够检测键盘事件。Ctrl+S调用保存函数
    if(k->modifiers()==Qt::ControlModifier&&k->key()==Qt::Key_S)
        saveActionSlot();
}

void MainWindow::mousePressEvent(QMouseEvent *m)
{
    QPoint pt = m->pos();
    qDebug()<<pt;
    if(m->button()==Qt::LeftButton)
        qDebug()<<"左键被按下";
    else if(m->button()==Qt::RightButton)
        qDebug()<<"右键被按下";
}