Archive:Development/Tutorials/Qt4 Ruby Tutorial/Chapter 3 (zh TW)

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• t3.rb

概覽

這個範例說明如何建立父（parent）widget 和子（child） widget。

我們將保持簡單性，只採用單一父 widget 和一個單獨的子 widget。

require 'Qt4'

app = Qt::Application.new(ARGV)

window = Qt::Widget.new() window.resize(200, 120)

quit = Qt::PushButton.new('Quit', window) quit.font = Qt::Font.new('Times', 18, Qt::Font::Bold) quit.setGeometry(10, 40, 180, 40) Qt::Object.connect(quit, SIGNAL('clicked()'), app, SLOT('quit()'))

window.show() app.exec()

一行一行的瀏覽

window = Qt::Widget.new()

在這裡，我們簡單地建立一個空白的 widget 物件。Qt::Widget 類別是所有使用者界面物件的基礎類別。widget 是使用者界面物件的原子：它接收滑鼠、鍵盤和其他來自視窗系統的事件，並在螢幕上描繪自身代表。widget 會被其父 widget 和在它前面的 widget 修剪。

一個沒有嵌入在父 widget 的 widget，像這樣的特殊 widget，被稱為視窗（window）。通常視窗會有視窗系統提供的外框和工作列（taskbar）項目。沒有父 widget 的 widget 就是一個獨立的視窗。其在螢幕上的初始位置是視窗系統所控制。

window.resize(200, 120)

我們設定視窗的寬為200像素，高為120像素。

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

A child is born. This Qt::PushButton is created with a parent widget (window). A child widget is always displayed within its parent's area. When displayed, it is clipped by its parent's bounds. By default, it is rooted at the top-left corner of its parent, at position (0, 0).

quit.setGeometry(10, 40, 180, 40)

The Qt::Widget::setGeometry() function takes four arguments: The first two arguments are the x and y coordinates of the button's top-left corner. The coordinates are relative to the parent widget. The last two arguments are the button's width and height. The result is a button that extends from position (10, 40) to position (190, 80).

window.show()

When a parent widget is shown, it will call show for all its children (except those that were explicitly hidden using Qt::Widget::hide()).

執行應用程式

The button no longer fills the entire window. Instead, it stays at position (10, 40) within the window and with a size of (180, 40), because of the Qt::Widget::setGeometry() call.

練習

Try resizing the window. How does the button change? What happens to the button's height if you run the program with a bigger font? What happens if you try to make the window really small?