返回介绍
文江博客 开发文档 ZetCode 教程整理 文章详情

Components in JRuby Swing

发布于 2025-02-22 22:19:50 字数 18909 浏览 0 评论 0 收藏 0

In this part of the JRuby Swing programming tutorial, we will cover basic Swing components.

Components are basic building blocks of a GUI application. Over the years, several components became a standard in all toolkits on all OS platforms. For example a button, a check box or a scroll bar. Swing has a rich set of components which covers most of the programming needs. More specialised components can be created as custom components.

JCheckBox

The JCheckBox is a component that has two states: on and off. The On state is visualised by a check mark. It is used to denote some boolean property. The JCheckBox component provides a check box with a text label.

#!/usr/local/bin/jruby

# ZetCode JRuby Swing tutorial
#
# This program uses JCheckBox
# component to show/hide the title
# of the window
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: December 2010

include Java

import java.awt.Dimension
import javax.swing.JCheckBox
import javax.swing.Box
import javax.swing.BoxLayout
import javax.swing.JFrame


class Example < JFrame
  
  def initialize
    super "JCheckBox example"
    
    self.initUI
  end
    
  def initUI
    
    self.setLayout BoxLayout.new getContentPane, BoxLayout::Y_AXIS
    self.add Box.createRigidArea Dimension.new 15, 20

    cb = JCheckBox.new "Show Title", true
    cb.setBounds 50, 60, 80, 30
    cb.setFocusable(false)

      
    cb.add_action_listener do |e|
      if self.getTitle.empty?
        self.setTitle "JCheckBox example"
      else
        self.setTitle ""
      end
    end
    
    add cb
    
    self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE
    self.setSize 300, 200
    self.setLocationRelativeTo nil
    self.setVisible true
  end
end

Example.new

In our example, we place a check box on the window. The check box shows or hides the title of the window.

self.setLayout BoxLayout.new getContentPane, BoxLayout::Y_AXIS
self.add Box.createRigidArea Dimension.new 15, 20

In this example, we use a BoxLayout layout manager. We put some space there, so that the check box is not too close to the corner.

cb = JCheckBox.new "Show Title", true

The JCheckBox component is created. The first parameter of the constructor is its text label. The second parameter is a boolean value indicating the initial selection state. If true the check box is selected.

cb.setFocusable false

We disable the focus for the check box. A JCheckBox that has a focus may be selected or unselected with a spacebar.

cb.add_action_listener do |e|
  if self.getTitle.empty?
    self.setTitle "JCheckBox example"
  else
    self.setTitle ""
  end
end

Inside the action listener, we check if the title is set. If there is a title, we remove it. If there is no title, we set one. This way we toggle the visibility of a title.

JCheckBox
Figure: JCheckBox

JLabel

The JLabel component is used to display text, image or both. No user interaction is available.

#!/usr/local/bin/jruby

# ZetCode JRuby Swing tutorial
#
# In this program, we show lyrics of a
# song in a window.
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: December 2010


include Java

import java.awt.BorderLayout
import java.awt.Color
import java.awt.Font

import javax.swing.JFrame
import javax.swing.BorderFactory
import javax.swing.JPanel
import javax.swing.JLabel


class Example < JFrame
  
  def initialize
    super "Lyrics"
    
    self.initUI
  end
    
  def initUI
    
    lyrics =  "<html>It's way too late to think of<br>
    Someone I would call now<br>
    And neon signs got tired<br>
    Red eye flights help the stars out<br>
    I'm safe in a corner<br>
    Just hours before me<br>
    <br>
    I'm waking with the roaches<br>
    The world has surrendered<br>
    I'm dating ancient ghosts<br>
    The ones I made friends with<br>
    The comfort of fireflies<br>
    Long gone before daylight<br>
    <br>
    And if I had one wishful field tonight<br>
    I'd ask for the sun to never rise<br>
    If God leant his voice for me to speak<br>
    I'd say go to bed, world<br>
    <br>
    I've always been too late<br>
    To see what's before me<br>
    And I know nothing sweeter than<br>
    Champaign from last New Years<br>
    Sweet music in my ears<br>
    And a night full of no fears<br>
    <br>
    But if I had one wishful field tonight<br>
    I'd ask for the sun to never rise<br>
    If God passed a mic to me to speak<br>
    I'd say stay in bed, world<br>
    Sleep in peace</html>"

    panel = JPanel.new
    panel.setLayout BorderLayout.new 10, 10

    label = JLabel.new lyrics
    label.setFont Font.new "Georgia", Font::PLAIN, 14
    label.setForeground Color.new 50, 50, 25

    panel.add label, BorderLayout::CENTER
    panel.setBorder BorderFactory.createEmptyBorder 10, 10, 10, 10
    self.add panel
    self.pack
    
    self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE
    self.setLocationRelativeTo nil
    self.setVisible true
  end  
end

Example.new

Our example shows lyrics of a song in the window. We can use HTML tags in JLabel component. We use the <br> tag to separate lines.

lyrics =  "<html>It's way too late to think of<br>
Someone I would call now<br>
And neon signs got tired<br>
...

We define a multi line text.

label = JLabel.new lyrics
label.setFont Font.new "Georgia", Font::PLAIN, 14

Here we create the label component. We set its font to plain Georgia, 14px tall.

panel.add label, BorderLayout::CENTER
panel.setBorder BorderFactory.createEmptyBorder 10, 10, 10, 10

We put the label into the center of the panel. We put 10px around the label.

JLabel component
Figure: JLabel component

JSlider

JSlider is a component that lets the user graphically select a value by sliding a knob within a bounded interval. Our example will show a volume control.

#!/usr/local/bin/jruby

# ZetCode JRuby Swing tutorial
#
# In this program we use a JSlider
# component to control volume images.
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: December 2010


include Java

import java.awt.Dimension
import java.awt.BorderLayout

import javax.swing.event.ChangeListener
import javax.swing.JFrame
import javax.swing.JSlider
import javax.swing.JLabel
import javax.swing.JPanel
import javax.swing.BorderFactory
import javax.swing.Box
import javax.swing.BoxLayout
import javax.swing.ImageIcon


class ChangeEvent
  include ChangeListener
  
  def setLabel label
    @label = label
  end  

  def setIcons mute, min, med, max
    @mute = mute
    @min = min
    @med = med
    @max = max
  end     
        
  
  def stateChanged e
    sender = e.getSource
     
    value = sender.getValue

    if value == 0
      @label.setIcon(@mute)
    elsif value > 0 and value <= 30
      @label.setIcon(@min)
    elsif value > 30 and value < 80
      @label.setIcon(@med)
    else
      @label.setIcon(@max)  
    end      
  end  
end



class Example < JFrame
  
  def initialize
    super "JSlider"
    
    self.initUI
  end
    
  def initUI
    
    mute = ImageIcon.new "mute.png"
    min = ImageIcon.new "min.png"
    med = ImageIcon.new "med.png"
    max = ImageIcon.new "max.png"

    panel = JPanel.new
    panel.setLayout BoxLayout.new panel, BoxLayout::X_AXIS
    panel.setBorder BorderFactory.createEmptyBorder 40, 40, 40, 40
    self.setLayout BorderLayout.new

    panel.add Box.createHorizontalGlue

    label = JLabel.new mute, JLabel::CENTER
        
    slider = JSlider.new 0, 150, 0
    
    ce = ChangeEvent.new
    ce.setLabel label
    ce.setIcons mute, min, med, max
    slider.add_change_listener ce
    
    slider.setPreferredSize Dimension.new 150, 30

    panel.add slider
    panel.add label
    panel.add Box.createRigidArea Dimension.new 5, 0
    
    panel.add Box.createHorizontalGlue
    self.add panel, BorderLayout::CENTER

    self.pack
    
    self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE
    self.setSize 300, 200
    self.setLocationRelativeTo nil
    self.setVisible true
  end
end

Example.new

In the code example, we show a JSlider and a JLabel . By dragging the slider, we change the icon on the label component. We have four images that represent various states of the sound.

mute = ImageIcon.new "mute.png"

Here we create an image icon.

panel.setLayout BoxLayout.new panel, BoxLayout::X_AXIS

Panel component has a horizontal BoxLayout .

panel.setBorder BorderFactory.createEmptyBorder 40, 40, 40, 40

We creare a 40px border around the panel.

panel.add Box.createHorizontalGlue

We put resizable space to both sides, left and right. It is to prevent JSlider from growing to unnatural sizes.

label = JLabel.new mute, JLabel::CENTER

This line creates a JLabel instance with the specified image and horizontal alignment. The label is centered vertically in its display area by default.

slider = JSlider.new 0, 150, 0

This is a JSlider constructor. The parameters are minimum value, maximum value and current value.

ce = ChangeEvent.new
ce.setLabel label
ce.setIcons mute, min, med, max

A ChangeEvent object is created. We set a label and icons to this object.

slider.add_change_listener ce

Each time we move the slider, the stateChanged method of the ChangeEvent object will be called.

panel.add Box.createRigidArea Dimension.new 5, 0

We place a 5px rigid space between the two components. They are too close to each other, when the slider is at the end position.

class ChangeEvent
  include ChangeListener

This is a ChangeEvent class, which implements the ChangeListener . As a consequence, this class must implement a changeEvent method.

sender = e.getSource
  
value = sender.getValue

Inside the changeEvent method, we get the event source. It is the slider, which has generated the event. From the sender, we get the current value.

if value == 0
  @label.setIcon(@mute)

If the value is equal to zero, we update the label to have a mute.png image.

JSlider
Figure: JSlider

JToggleButton

JToggleButton is a button that has two states. Pressed and not pressed. You toggle between these two states by clicking on it. There are situations where this functionality fits well.

#!/usr/local/bin/jruby

# ZetCode JRuby Swing tutorial
#
# This program uses toggle buttons to
# change the background color of
# a panel.
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: December 2010

include Java

import java.awt.Color
import java.awt.Dimension
import java.awt.event.ActionListener
import javax.swing.JToggleButton
import javax.swing.Box
import javax.swing.BoxLayout
import javax.swing.BorderFactory
import javax.swing.JFrame
import javax.swing.JPanel
import javax.swing.border.LineBorder


class Example < JFrame
  include ActionListener
  
  def initialize
    super "JToggleButton"
    
    self.initUI
  end
    
  def initUI
    
    self.setPreferredSize Dimension.new 280, 200

    bottom = JPanel.new
    bottom.setLayout BoxLayout.new bottom, BoxLayout::X_AXIS
    bottom.setBorder BorderFactory.createEmptyBorder 20, 20, 20, 20

    leftPanel = JPanel.new
    leftPanel.setLayout BoxLayout.new leftPanel, BoxLayout::Y_AXIS

    @display = JPanel.new
    @display.setPreferredSize Dimension.new 110, 110
    @display.setBorder LineBorder.createGrayLineBorder
    @display.setBackground Color.black

    bottom.add @display
      
    redButton = JToggleButton.new "red"
    redButton.addActionListener self
    greenButton = JToggleButton.new "green"
    greenButton.addActionListener self
    blueButton = JToggleButton.new "blue"
    blueButton.addActionListener self
    

    blueButton.setMaximumSize greenButton.getMaximumSize
    redButton.setMaximumSize greenButton.getMaximumSize

    leftPanel.add redButton
    leftPanel.add Box.createRigidArea Dimension.new 25, 7
    leftPanel.add greenButton
    leftPanel.add Box.createRigidArea Dimension.new 25, 7
    leftPanel.add blueButton    

    bottom.add leftPanel
    bottom.add Box.createRigidArea Dimension.new 20, 0

    self.add bottom
    self.pack
    
    self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE
    self.setSize 300, 200
    self.setLocationRelativeTo nil
    self.setVisible true
  end
  
  def actionPerformed e
        
    color = @display.getBackground
    red = color.getRed
    green = color.getGreen
    blue = color.getBlue

    if e.getActionCommand == "red"
      if red == 0
        red = 255
      else
        red = 0
      end
    end

    if e.getActionCommand == "green"
      if green == 0
        green = 255
      else
        green = 0
      end
    end

    if e.getActionCommand == "blue"
      if blue == 0
        blue = 255
      else
        blue = 0
      end      
    end

    setCol = Color.new red, green, blue
    @display.setBackground setCol    
  end    
end

Example.new

In the code example, we use three toggle buttons to change the color of a rectangular component.

class Example < JFrame
  include ActionListener

The class implements the ActionListener . We will do some action in the actionPerformed method of the Example class.

redButton = JToggleButton.new "red"
redButton.addActionListener self

We create a JToggleButton component. We add an action listener to the button. The action listener is the Example class. When we click on the redButton, the actionPerformed method of the Example class will be called.

blueButton.setMaximumSize greenButton.getMaximumSize
redButton.setMaximumSize greenButton.getMaximumSize

We make all three buttons of equal size.

color = @display.getBackground
red = color.getRed
green = color.getGreen
blue = color.getBlue

We determine the current red, green, blue parts of the display background color.

if e.getActionCommand == "red"
  if red == 0
    red = 255
  else
    red = 0
  end
end

We determine, which button was toggled, and update the color part of the RGB value accordingly.

setCol = Color.new red, green, blue
@display.setBackground setCol

Here a new color is created and the display panel is updated to a new color.

JToggleButton
Figure: JToggleButton

JList

JList is a component that displays a list of objects. It allows the user to select one or more items.

#!/usr/local/bin/jruby

# ZetCode JRuby Swing tutorial
#
# In this program, we show all 
# available fonts of a system in 
# a JList component.
#
# author: Jan Bodnar
# website: www.zetcode.com
# last modified: December 2010

include Java


import java.awt.BorderLayout
import java.awt.Dimension
import java.awt.Font
import java.awt.GraphicsEnvironment

import javax.swing.JFrame
import javax.swing.BorderFactory
import javax.swing.JScrollPane
import javax.swing.JPanel
import javax.swing.JLabel
import javax.swing.JList


class Example < JFrame
  
  def initialize
  super "JList"
  
  initUI
  end
  
  def initUI
  
  panel = JPanel.new
  panel.setLayout BorderLayout.new
  panel.setBorder BorderFactory.createEmptyBorder 20, 20, 20, 20

  ge = GraphicsEnvironment.getLocalGraphicsEnvironment
  fonts = ge.getAvailableFontFamilyNames

  list = JList.new fonts

  list.add_list_selection_listener do |e|

    sender = e.source

    if not e.getValueIsAdjusting
      name = sender.getSelectedValue
      font = Font.new name, Font::PLAIN, 13
      @label.setFont font
    end
  end

  pane = JScrollPane.new
  pane.getViewport.add list
  pane.setPreferredSize Dimension.new 250, 200
  panel.add pane

  @label = JLabel.new "Aguirre, der Zorn Gottes"
  @label.setFont Font.new "Serif", Font::PLAIN, 12
  self.add @label, BorderLayout::SOUTH

  self.add panel
  self.pack
  
  self.setDefaultCloseOperation JFrame::EXIT_ON_CLOSE
  self.setLocationRelativeTo nil
  self.setVisible true
  end
  
end

Example.new

In our example, we will display a JList and a JLabel components. The list component contains a list of all available font family names on our system. If we select an item from the list, the label will be displayed in a font, we have chosen.

ge = GraphicsEnvironment.getLocalGraphicsEnvironment
fonts = ge.getAvailableFontFamilyNames

Here we obtain all possible font family names on our system.

list = JList.new fonts

We create an instance of the JList component. It will display all font family names.

if not e.getValueIsAdjusting

Events in list selection are grouped. We receive events for both selecting and unselecting. To filter only the selecting events, we use the getValueIsAdjusting method.

name = sender.getSelectedValue
font = Font.new name, Font::PLAIN, 13
@label.setFont font

We get the selected item and set a new font for the label.

pane = JScrollPane.new
pane.getViewport.add list

JList component is not scrollable by default. We put the list into the JScrollPane to make it scrollable.

JList component
Figure: JList component

In this part of the JRuby Swing tutorial, we have presented several Swing components.

如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

扫码二维码加入Web技术交流群

发布评论

需要 登录 才能够评论， 你可以免费 注册 一个本站的账号。
列表为空，暂无数据
    我们使用 Cookies 和其他技术来定制您的体验包括您的登录状态等。通过阅读我们的 隐私政策 了解更多相关信息。 单击 接受 或继续使用网站，即表示您同意使用 Cookies 和您的相关数据。
    原文