【C/C++学院】（19）QT版：记事本

利用主窗口类实现，QT版：记事本。

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QCloseEvent>
#include <QTextEdit>
#include <QMenu>
#include <QMenuBar>
#include <QAction>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
private slots:
    void openfile();
    void newfile();
    void savefile();
    void exitfile();
    void copyfile();
    void cutfile();
    void pastefile();

private:
    void createMenus();
    void createActions();
    void closeEvent(QCloseEvent *event);
    QTextEdit *text;
    QMenu *fileMenu;
    QMenu *editMenu;
    QAction *openFileAction;
    QAction *newFileAction;
    QAction *saveFileAction;
    QAction *exitFileAction;
    QAction *copyFileAction;
    QAction *cutFileAction;
    QAction *pasteFileAction;

};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include <QMessageBox>
#include <QFileDialog>
#include <QTextStream>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    setWindowTitle("记事本");
    text = new QTextEdit(this);
    this->setCentralWidget(text);
    text->setFontPointSize(20);//设置默认字体大小
    createActions();
    createMenus();

}

MainWindow::~MainWindow()
{

}

void MainWindow::openfile()
{
    QString filename = QFileDialog::getOpenFileName(this, tr("打开文件"));
    if (filename.isEmpty())//如果没有选择要打开的文件名，函数退出
    {
        return ;
    }
    QFile data(filename);
    if (data.open(QFile::ReadOnly))//以只读方式打开文件
    {
        text->clear();//首先将text空间内容清空
        QTextStream stream(&data);
        while (!stream.atEnd())//循环读取文件按，直到文件尾结束循环
        {
            text->append(stream.readLine());//在text控件内容尾部追加从文件中读取的内容
        }
        data.close();//读完文件后关闭文件
    }else
    {
        QMessageBox::critical(this, tr("错误"), data.errorString());
    }
}

void MainWindow::newfile()
{
    text->clear();
}

void MainWindow::savefile()
{
    QString filename = QFileDialog::getSaveFileName(this, tr("保存文件"));
    if (filename.isEmpty())//如果没有选择文件，函数退出
    {
        return ;
    }
    QFile data(filename);
    if (data.open(QFile::WriteOnly | QFile::Truncate))//以写方式打开文件，如果关键存在，则是追加模式
    {
        QTextStream stream(&data);
        stream<<text->toPlainText();//将text控件内容转化为QString后，写入文件
        data.close();
    }
    else
    {
        QMessageBox::critical(this, tr("错误"), data.errorString());
    }
}

void MainWindow::exitfile()
{
    close();
    //exit(0);//直接退出
}

void MainWindow::copyfile()
{
    text->copy();
}

void MainWindow::cutfile()
{
    text->cut();
}

void MainWindow::pastefile()
{
    text->paste();
}

void MainWindow::createMenus()
{
    fileMenu = menuBar()->addMenu(tr("文件"));//建立文件菜单
    fileMenu->addAction(openFileAction);
    fileMenu->addAction(newFileAction);
    fileMenu->addAction(saveFileAction);
    fileMenu->addSeparator();//加入一个分隔符
    fileMenu->addAction(exitFileAction);

    editMenu = menuBar()->addMenu(tr("编辑"));
    editMenu->addAction(copyFileAction);
    editMenu->addAction(cutFileAction);
    editMenu->addAction(pasteFileAction);
}

void MainWindow::createActions()
{
    openFileAction = new QAction(tr("打开"), this);
    openFileAction->setShortcut(tr("Ctrl+o"));
    connect(openFileAction, SIGNAL(triggered()), this, SLOT(openfile()));

    newFileAction = new QAction(tr("新建"), this);
    newFileAction->setShortcut(tr("Ctrl+N"));
    connect(newFileAction, SIGNAL(triggered()), this, SLOT(newfile()));

    saveFileAction = new QAction(tr("保存"), this);
    saveFileAction->setShortcut(tr("Ctrl+s"));
    connect(saveFileAction, SIGNAL(triggered()), this, SLOT(savefile()));

    exitFileAction = new QAction(tr("退出"), this);
    exitFileAction->setShortcut(tr("Ctrl+q"));
    connect(exitFileAction, SIGNAL(triggered()), this, SLOT(exitfile()));

    copyFileAction = new QAction(tr("复制"), this);
    copyFileAction->setShortcut(tr("Ctrl+c"));
    connect(copyFileAction, SIGNAL(triggered()), this, SLOT(copyfile()));

    cutFileAction = new QAction(tr("剪切"), this);
    cutFileAction->setShortcut(tr("Ctrl+x"));
    connect(cutFileAction, SIGNAL(triggered()), this, SLOT(cutfile()));

    pasteFileAction = new QAction(tr("粘贴"), this);
    pasteFileAction->setShortcut(tr("Ctrl+v"));
    connect(pasteFileAction, SIGNAL(triggered()), this, SLOT(pastefile()));
}

void MainWindow::closeEvent(QCloseEvent *event)
{
    QMessageBox::StandardButton button;
    button = QMessageBox::question(this, tr("退出程序"), QString(tr("是否退出")),
                                   QMessageBox::Yes | QMessageBox::No);
    if (button == QMessageBox::Yes)
    {
        event->accept();//接受退出信号，程序退出
    }else
    {
        event->ignore();//忽略退出信息，程序继续运行
    }
}

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

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

    w.resize(600, 400);
    w.show();

    return a.exec();
}