Development/Tutorials/Qt4 Ruby Tutorial/Chapter 2/ru: Difference between revisions

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    This time, the button says <strong>Quit</strong> and that's exactly what the program will do when the user clicks the button.
    На этот раз кнопка называется <strong>Quit</strong> (Выход), это именно то, что она будет делать.


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    Revision as of 17:00, 2 July 2011

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    Development/Tutorials/Qt4 Ruby Tutorial/Chapter 2


    Выход по нажатию
    Серия примеров   Введение в программирование на Qt®4 на языке Ruby
    Необходимо знать   Пример 1: Здравствуй, мир!
    Следующий пример   Пример 3: Иерархия виджетов
    Литература   нет

    Выход по нажатию

    Файлы:

    Обзор

    Уже создав окно в первой главе, мы заставим приложение корректно завершаться по нажатию кнопки.

    Кроме того, мы научимся менять шрифт.

    require 'Qt4'
    
    app = Qt::Application.new(ARGV)
    
    quit = Qt::PushButton.new('Quit')
    quit.resize(75, 30)
    quit.setFont(Qt::Font.new('Times', 18, Qt::Font::Bold))
    
    Qt::Object.connect(quit, SIGNAL('clicked()'), app, SLOT('quit()'))
    
    quit.show()
    app.exec()
    

    Построчный обзор программы

    quit = Qt::PushButton.new('Quit')
    

    На этот раз кнопка называется Quit (Выход), это именно то, что она будет делать.

    quit.resize(75, 30)
    

    We've chosen another size for the button since the text is a bit shorter than "Hello world!". We could also have used Qt::FontMetrics to set right size, or let Qt::PushButton choose a reasonable default.

    quit.setFont(Qt::Font.new('Times', 18, Qt::Font::Bold))
    

    Here we choose a new font for the button, an 18-point bold font from the Times family. It is also possible to change the default font for the entire application, using Qt::Application::setFont().

    Qt::Object.connect(quit, SIGNAL('clicked()'), app, SLOT('quit()'))
    

    Qt::Object::connect() is perhaps the most central feature of Qt. Note that connect() in this context is a static function in Qt::Object. Do not confuse it with the connect() function in the Berkeley socket library.

    This connect() call establishes a one-way connection between two Qt objects (objects that inherit Qt::Object, directly or indirectly). Every Qt object can have both signals (to send messages) and slots (to receive messages). All widgets are Qt objects, since they inherit Qt::Widget, which in turn inherits Qt::Object.

    Here, the clicked() signal of quit is connected to the quit() slot of app, so that when the button is clicked, the application quits.

    The Signals and Slots documentation describes this topic in detail.

    Running the Application

    When you run this program, you will see an even smaller window than in Chapter 1, filled with an even smaller button.

    Exercises

    Try to resize the window. Click the button to close the application.

    Are there any other signals in Qt::PushButton you can connect to quit? [Hint: The Qt::PushButton inherits most of its functionality from Qt::AbstractButton.]