【Qt入门教程06】官方入门教程|番外篇

～风介～

code one：

//main.cpp
#include <QtWidgets>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QTextEdit textEdit;
    textEdit.show();

    return app.exec();
}

code two：

//main.cpp
#include <QtWidgets>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QTextEdit *textEdit = new QTextEdit;
    QPushButton *quitButton = new QPushButton("&Quit");

    QObject::connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit()));

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(textEdit);
    layout->addWidget(quitButton);

    QWidget window;
    window.setLayout(layout);

    window.show();

    return app.exec();
}

code three：

//main.cpp
#include <QtWidgets>

class Notepad : public QWidget
{
    Q_OBJECT

public:
    Notepad();

private slots:
    void quit();

private:
    QTextEdit *textEdit;
    QPushButton *quitButton;

};

Notepad::Notepad()
{
    textEdit = new QTextEdit;
    quitButton = new QPushButton(tr("Quit"));

    connect(quitButton, SIGNAL(clicked()), this, SLOT(quit()));

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(textEdit);
    layout->addWidget(quitButton);

    setLayout(layout);

    setWindowTitle(tr("Notepad"));
}

void Notepad::quit()
{
    QMessageBox messageBox;
    messageBox.setWindowTitle(tr("Notepad"));
    messageBox.setText(tr("Do you really want to quit?"));
    messageBox.setStandardButtons(QMessageBox::Yes | QMessageBox::No);
    messageBox.setDefaultButton(QMessageBox::No);
    if (messageBox.exec() == QMessageBox::Yes)
        qApp->quit();
}

int main(int argc, char **argv)
{
    QApplication app(argc, argv);

    Notepad notepad;
    notepad.show();

    return app.exec();
}

code four:

//main.cpp
#include <QtWidgets>

class Notepad : public QMainWindow
{
    Q_OBJECT

public:
    Notepad();

private slots:
    void load();
    void save();

private:
    QTextEdit *textEdit;

    QAction *loadAction;
    QAction *saveAction;
    QAction *exitAction;

    QMenu *fileMenu;
};

Notepad::Notepad()
{

    loadAction = new QAction(tr("&Load"), this);
    saveAction = new QAction(tr("&Save"), this);
    exitAction = new QAction(tr("E&xit"), this);

    connect(loadAction, SIGNAL(triggered()), this, SLOT(load()));
    connect(saveAction, SIGNAL(triggered()), this, SLOT(save()));
    connect(exitAction, SIGNAL(triggered()), qApp, SLOT(quit()));

    fileMenu = menuBar()->addMenu(tr("&File"));
    fileMenu->addAction(loadAction);
    fileMenu->addAction(saveAction);
    fileMenu->addSeparator();
    fileMenu->addAction(exitAction);

    textEdit = new QTextEdit;
    setCentralWidget(textEdit);

    setWindowTitle(tr("Notepad"));
}

void Notepad::load()
{

}

void Notepad::save()
{

}

int main(int argc, char **argv)
{
    QApplication app(argc, argv);

    Notepad notepad;
    notepad.show();

    return app.exec();
};

code five:

//main.cpp
#include <QtWidgets>

class Notepad : public QMainWindow
{
    Q_OBJECT

public:
    Notepad();

private slots:
    void open();
    void save();

private:
    QTextEdit *textEdit;

    QAction *openAction;
    QAction *saveAction;
    QAction *exitAction;

    QMenu *fileMenu;
};

Notepad::Notepad()
{

    openAction = new QAction(tr("&Load"), this);
    saveAction = new QAction(tr("&Save"), this);
    exitAction = new QAction(tr("E&xit"), this);

    connect(openAction, SIGNAL(triggered()), this, SLOT(open()));
    connect(saveAction, SIGNAL(triggered()), this, SLOT(save()));
    connect(exitAction, SIGNAL(triggered()), qApp, SLOT(quit()));

    fileMenu = menuBar()->addMenu(tr("&File"));
    fileMenu->addAction(openAction);
    fileMenu->addAction(saveAction);
    fileMenu->addSeparator();
    fileMenu->addAction(exitAction);

    textEdit = new QTextEdit;
    setCentralWidget(textEdit);

    setWindowTitle(tr("Notepad"));
}

void Notepad::open()
{
    QString fileName = QFileDialog::getOpenFileName(this, tr("Open File"), "",
        tr("Text Files (*.txt);;C++ Files (*.cpp *.h)"));

    if (!fileName.isEmpty()) {
        QFile file(fileName);
        if (!file.open(QIODevice::ReadOnly)) {
            QMessageBox::critical(this, tr("Error"), tr("Could not open file"));
            return;
        }
        QTextStream in(&file);
        textEdit->setText(in.readAll());
        file.close();
    }
}

void Notepad::save()
{

    QString fileName = QFileDialog::getSaveFileName(this, tr("Save File"), "",
        tr("Text Files (*.txt);;C++ Files (*.cpp *.h)"));

    if (!fileName.isEmpty()) {
        QFile file(fileName);
        if (!file.open(QIODevice::WriteOnly)) {
            // error message
        } else {
            QTextStream stream(&file);
            stream << textEdit->toPlainText();
            stream.flush();
            file.close();
        }
    }
}

int main(int argc, char **argv)
{
    QApplication app(argc, argv);

    Notepad notepad;
    notepad.show();

    return app.exec();
}