Java Swing 教程使用 SwingUtilities.invokeLater 创建 GUI（如此处）。这里解释了为什么这样做- 大多数 Swing 对象都不是线程安全的。另一方面，我见过的大多数 JRuby Swing 示例只是设置脚本中可见的顶部框架（就像这里- 存档中的“guis”目录）。

问题是，在 JRuby 脚本中创建应用程序顶部框架时，我是否应该遵循使用 SwingUtilities.invokeLater() 的 Java 模式？

我有两个 JRuby 脚本，一个使用 SwingUtilities.invokeLater()，另一个不使用：

java_import javax.swing.JFrame
java_import javax.swing.SwingUtilities
java_import java.awt.Dimension
java_import javax.swing.JButton
JavaThread = java.lang.Thread

class TopFrame < JFrame

  def initialize
    super
    init_components()

    pack()
    set_visible(true)

    puts '----------------------------------------'
    puts 'In JFrame constructor:'
    puts "Thread name: #{JavaThread.current_thread.name}"
    puts "Is event dispatch thread: #{SwingUtilities.event_dispatch_thread?}"
    JavaThread.current_thread.thread_group.list

  end

  def init_components()

    set_default_close_operation(JFrame::EXIT_ON_CLOSE)
    set_preferred_size(Dimension.new(400, 300))

    button = JButton.new('Button')
    button.add_action_listener do |event|
      puts '----------------------------------------'
      puts 'In action listener:'
      puts "Thread name: #{JavaThread.current_thread.name}"
      puts "Is event dispatch thread: #{SwingUtilities.event_dispatch_thread?}"
      JavaThread.current_thread.thread_group.list
    end

    get_content_pane.add(button)

  end

end

puts '----------------------------------------'
puts 'Before SwingUtilties.invokeLater():'
puts "Thread name: #{JavaThread.current_thread.name}"
puts "Is event dispatch thread: #{SwingUtilities.event_dispatch_thread?}"
JavaThread.current_thread.thread_group.list

SwingUtilities.invoke_later do
  TopFrame.new
end

puts '----------------------------------------'
puts 'After SwingUtilities.invokeLater():'
puts "Thread name: #{JavaThread.current_thread.name}"
puts "Is event dispatch thread: #{SwingUtilities.event_dispatch_thread?}"
JavaThread.current_thread.thread_group.list

输出是：

----------------------------------------
Before SwingUtilties.invokeLater():
Thread name: main
Is event dispatch thread: false
java.lang.ThreadGroup[name=main,maxpri=10]
    Thread[main,5,main]
    Thread[Ruby-0-JIT-1,1,main]
    java.lang.ThreadGroup[name=Ruby Threads#11483240,maxpri=10]
----------------------------------------
After SwingUtilities.invokeLater():
Thread name: main
Is event dispatch thread: false
java.lang.ThreadGroup[name=main,maxpri=10]
    Thread[main,5,main]
    Thread[Ruby-0-JIT-1,1,main]
    Thread[AWT-EventQueue-0,6,main]
    java.lang.ThreadGroup[name=Ruby Threads#11483240,maxpri=10]
----------------------------------------
In JFrame constructor:
Thread name: AWT-EventQueue-0
Is event dispatch thread: true
java.lang.ThreadGroup[name=main,maxpri=10]
    Thread[AWT-EventQueue-0,6,main]
    Thread[DestroyJavaVM,5,main]
    java.lang.ThreadGroup[name=Ruby Threads#11483240,maxpri=10]
----------------------------------------
In action listener:
Thread name: AWT-EventQueue-0
Is event dispatch thread: true
java.lang.ThreadGroup[name=main,maxpri=10]
    Thread[AWT-EventQueue-0,6,main]
    Thread[DestroyJavaVM,5,main]
    java.lang.ThreadGroup[name=Ruby Threads#11483240,maxpri=10]

在调用 SwingUtilities.invokeLater() 之前，EDT 不存在。在 SwingUtilities.invokeLater() 之后，EDT 存在，并且与当前线程不同。在 JFrame 构造函数和 JButton 操作事件侦听器中，EDT 是当前线程。

另一个脚本不使用 SwingUtilities.invokeLater()：

java_import javax.swing.JFrame
java_import javax.swing.SwingUtilities
java_import java.awt.Dimension
java_import javax.swing.JButton
JavaThread = java.lang.Thread

puts '----------------------------------------'
puts 'Before JFrame.new():'
puts "Thread name: #{JavaThread.current_thread.name}"
puts "Is event dispatch thread: #{SwingUtilities.event_dispatch_thread?}"
JavaThread.current_thread.thread_group.list

frame = JFrame.new()

frame.set_default_close_operation(JFrame::EXIT_ON_CLOSE)
frame.set_preferred_size(Dimension.new(400, 300))

button = JButton.new('Button')
button.add_action_listener do |event|
  puts '----------------------------------------'
  puts 'In action listener:'
  puts "Thread name: #{JavaThread.current_thread.name}"
  puts "Is event dispatch thread: #{SwingUtilities.event_dispatch_thread?}"
  JavaThread.current_thread.thread_group.list
end

frame.get_content_pane.add(button)
frame.pack()

puts '----------------------------------------'
puts 'Before JFrame.setVisible():'
puts "Thread name: #{JavaThread.current_thread.name}"
puts "Is event dispatch thread: #{SwingUtilities.event_dispatch_thread?}"
JavaThread.current_thread.thread_group.list

frame.set_visible(true)

输出是：

----------------------------------------
Before JFrame.new():
Thread name: main
Is event dispatch thread: false
java.lang.ThreadGroup[name=main,maxpri=10]
    Thread[main,5,main]
    Thread[Ruby-0-JIT-1,1,main]
    java.lang.ThreadGroup[name=Ruby Threads#11483240,maxpri=10]
----------------------------------------
Before JFrame.setVisible():
Thread name: main
Is event dispatch thread: false
java.lang.ThreadGroup[name=main,maxpri=10]
    Thread[main,5,main]
    Thread[Ruby-0-JIT-1,1,main]
    Thread[AWT-EventQueue-0,6,main]
    java.lang.ThreadGroup[name=Ruby Threads#11483240,maxpri=10]
----------------------------------------
In action listener:
Thread name: AWT-EventQueue-0
Is event dispatch thread: true
java.lang.ThreadGroup[name=main,maxpri=10]
    Thread[AWT-EventQueue-0,6,main]
    Thread[DestroyJavaVM,5,main]
    java.lang.ThreadGroup[name=Ruby Threads#11483240,maxpri=10]

EDT是在JFrame构造函数之后创建的，不是当前线程。在 JButton 事件监听器中，EDT 是当前线程。

解决方案

consider JRuby as any other JVM language ... with no special care for Swing/AWT conventions built-in - only a "new" syntax for writing a Swing GUI. as such do care about EDT just like you would in Java.