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POScala Swing Box Subscribes Multiple Events
 

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  1. POScala Swing Box Subscribes Multiple Events
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    <p>I'm writing a GUI in Scala, and I've run across a strange problem while trying to register Button Events in a <code>foreach</code> statement: It should be that for every element <i>object<sub>i</sub></i> in a list of objects (<i>object<sub>0</sub></i> ... <i>object<sub>n</sub></i>), a corresponding Button <i>x = button<sub>i</sub></i> is retrieved and a given Box is subscribed to it with <code>box.listenTo(x)</code>. When the Button is pushed, some action related to the <i>object<sub>i</sub></i> should be performed (in this case, <code>println("Event triggered: " + event)</code>):</p> <pre><code>import scala.swing.ComboBox import scala.collection.mutable.Buffer import scala.swing.Button import scala.swing.event.ButtonClicked import scala.swing.Action import scala.swing.SimpleSwingApplication import scala.swing.MainFrame import scala.swing.GridPanel import scala.swing.BorderPanel object EventSet extends SimpleSwingApplication { object PhoneKeyEvent extends Enumeration { val Key1 = Value("1") val Key2 = Value("2") } /* Constants */ private val DisplayHistory = Buffer[String]() private val KeypadKeyEvents = List( PhoneKeyEvent.Key1, PhoneKeyEvent.Key2) private val PhoneKeyEventButtonNames = Map( PhoneKeyEvent.Key1 -&gt; "1", PhoneKeyEvent.Key2 -&gt; "2" ) /* End constants */ private var PhoneKeyEventButtons = Map[PhoneKeyEvent.Value, Button]() private def createDisplay() : ComboBox[String] = { new ComboBox(DisplayHistory) { // Listen to keypad keys // Get the set of all keypad key events val keypadEvents = List(PhoneKeyEvent.Key1, PhoneKeyEvent.Key2) println("keypadEvents: " + keypadEvents) keypadEvents.foreach({ event =&gt; println("event: " + event) // Listen to each button representing a keypad key event var keypadEventButton = PhoneKeyEventButtons(event) println("keypadEventButton: " + keypadEventButton) listenTo(keypadEventButton) reactions += { case ButtonClicked(keypadEventButton) =&gt; { // TODO: fix strange bug here: adds all possible inputs println("Event triggered: " + event) // selection.item = selection.item + event } } }) } } private def createPhoneControllerPanel() : BorderPanel = { new BorderPanel() { val keypadControlPanel = createPhoneKeyEventTypeControlPanel(KeypadKeyEvents) add(keypadControlPanel, BorderPanel.Position.Center) add(createDisplay(), BorderPanel.Position.North) focusable = true requestFocus } } /** * Creates a new {@link Button} for a given {@link PhoneKeyEvent} and adds * the button to the global map of such buttons to their respective events; * that means multiple buttons cannot be created for the same key event. */ private def createPhoneKeyEventButton(phoneKeyEvent: PhoneKeyEvent.Value) : Button = { // Only one button can be created per key event require(!PhoneKeyEventButtons.contains(phoneKeyEvent), {System.err.println("A Button for the PhoneKeyEvent " + phoneKeyEvent + "has already been created.")}) val keyEventButtonName = PhoneKeyEventButtonNames(phoneKeyEvent) val result = new Button(Action(keyEventButtonName) { println("Key event button pressed: " + phoneKeyEvent) }) // Add the button to the map of all created key event buttons PhoneKeyEventButtons += phoneKeyEvent -&gt; result return result } private def createPhoneKeyEventTypeControlPanel(keyEvents : Iterable[PhoneKeyEvent.Value]) : GridPanel = { new GridPanel(4, 3) { // Get the intersection of all key events of the given type and the events with button names keyEvents.foreach(phoneKeyEvent =&gt; contents += createPhoneKeyEventButton(phoneKeyEvent)) } } override def top = new MainFrame { contents = createPhoneControllerPanel() } } </code></pre> <p>However, I get some very strange behaviour, where clicking any Button results in <i>all</i> such object actions are triggered -- See the program output:</p> <pre><code>keypadEvents: List(1, 2) event: 1 keypadEventButton: scala.swing wrapper scala.swing.Button$$anon$1[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.5,border= javax.swing.plaf.BorderUIResource$CompoundBorderUIResource@7633f09,flags=296,maximumSize=,minimumSize=,preferredSize=,de faultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=2,left=14,bottom=2,right=14] ,paintBorder=true,paintFocus=true,pressedIcon=,rolloverEnabled=true,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,te xt=1,defaultCapable=true] event: 2 keypadEventButton: scala.swing wrapper scala.swing.Button$$anon$1[,0,0,0x0,invalid,alignmentX=0.0,alignmentY=0.5,border= javax.swing.plaf.BorderUIResource$CompoundBorderUIResource@7633f09,flags=296,maximumSize=,minimumSize=,preferredSize=,de faultIcon=,disabledIcon=,disabledSelectedIcon=,margin=javax.swing.plaf.InsetsUIResource[top=2,left=14,bottom=2,right=14] ,paintBorder=true,paintFocus=true,pressedIcon=,rolloverEnabled=true,rolloverIcon=,rolloverSelectedIcon=,selectedIcon=,te xt=2,defaultCapable=true] Key event button pressed: 1 Event triggered: 1 Event triggered: 2 Key event button pressed: 2 Event triggered: 1 Event triggered: 2 </code></pre> <p>I'm completely at a loss as to why this is happening; I'm quite new at Scala anyway, so it's quite unfamiliar territory, but I've tried fiddling with a lot of stuff and snooped around in the Swing source code, and still clueless... how can <i>every</i> value of a reference inside of a loop be used in every iteration? or how can every event be triggered by Swing at once? or...?</p> <p><strong>Edit:</strong> Here are two minimised versions, both of which behave differently:</p> <pre><code>import scala.swing.SimpleSwingApplication object ButtonEvents extends SimpleSwingApplication { import scala.swing.Button import scala.swing.event.ButtonClicked import scala.swing.Action import scala.swing.MainFrame import scala.swing.FlowPanel override def top = new MainFrame { contents = new FlowPanel { val button1 = new Button(Action("1") { println("Button 1 pressed") }) contents += button1 val button2 = new Button(Action("2") { println("Button 2 pressed") }) contents += button2 val buttons = List(button1, button2) buttons.foreach({ button =&gt; listenTo(button) reactions += { case ButtonClicked(button) =&gt; { println("Event triggered: " + button.text) } } }) } } </code></pre> <p>}</p> <p>Prints:</p> <pre><code>Button 1 pressed Event triggered: 1 Event triggered: 1 Button 2 pressed Event triggered: 2 Event triggered: 2 </code></pre> <p>And a version which seems to behave correctly (but I'm not sure why):</p> <pre><code>import scala.swing.SimpleSwingApplication object ButtonEvents extends SimpleSwingApplication { import scala.swing.Button import scala.swing.event.ButtonClicked import scala.swing.Action import scala.swing.MainFrame import scala.swing.FlowPanel override def top = new MainFrame { contents = new FlowPanel { val button1 = new Button(Action("1") { println("Button 1 pressed") }) contents += button1 val button2 = new Button(Action("2") { println("Button 2 pressed") }) contents += button2 val buttons = Map("1" -&gt; button1, "2" -&gt; button2) buttons.foreach({ eventButton =&gt; listenTo(eventButton._2) reactions += { case ButtonClicked(eventButton._2) =&gt; { println("Event triggered: " + eventButton._1) } } }) } } } </code></pre> <p>Prints (correct):</p> <pre><code>Button 1 pressed Event triggered: 1 Button 2 pressed Event triggered: 2 </code></pre>
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    1. COtl;dr - you should boil down the code to the essence of the problem
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    2. COThe problem is that when I try to "boil down the code" I get different (but related) behaviour, and I don't know where the difference is: Here are two different versions which behave differently from above:
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