Bug? XCLV Index out of bounds exception when removing the last item (or is it me?)

[walt61]

See title; the attached demo project shows what happens, and this exception occurs (only when removing the last item, removing any others works fine):

Spoiler

Call B4XPages.GetManager.LogEvents = True to enable logging B4XPages events.
customlistview._getrawlistitem (java line: 449)
java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:100)
at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
at java.base/java.util.Objects.checkIndex(Objects.java:385)
at java.base/java.util.ArrayList.get(ArrayList.java:427)
at anywheresoftware.b4a.objects.collections.List.Get(List.java:122)
at b4j.example.customlistview._getrawlistitem(customlistview.java:449)
at b4j.example.customlistview$ResumableSub_PanelClickHandler.resume(customlistview.java:775)
at b4j.example.customlistview._panelclickhandler(customlistview.java:751)
at b4j.example.customlistview._panel_mouseclicked(customlistview.java:742)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:578)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:117)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:104)
at anywheresoftware.b4j.objects.NodeWrapper$1.handle(NodeWrapper.java:109)
at anywheresoftware.b4j.objects.NodeWrapper$1.handle(NodeWrapper.java:1)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3602)
at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3906)
at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1878)
at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2623)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:411)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:301)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:450)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:424)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:449)
at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:557)
at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:943)
at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
at java.base/java.lang.Thread.run(Thread.java:1589)

The code is (I've only tested it with B4J):

Spoiler

Sub Class_Globals
Private Root As B4XView
Private xui As XUI
Private CustomListView1 As CustomListView
Private Label1 As Label ' Is from layout 'clvrow' and sits in a Pane
End Sub

Public Sub Initialize
End Sub

Private Sub B4XPage_Created (Root1 As B4XView)
Root = Root1
Root.LoadLayout("MainPage")
End Sub

Private Sub B4XPage_Appear

Dim i As Int
For i = 0 To 5
Wait For (CreateClvItem(i)) Complete(pnl As B4XView)
CustomListView1.Add(pnl, pnl.Tag)
Sleep(0)
Next

End Sub

Private Sub CreateClvItem(i As Int) As ResumableSub

Dim p As B4XView = xui.CreatePanel("")
p.SetLayoutAnimated(0, 0, 0, CustomListView1.AsView.Width, 50dip)
p.LoadLayout("clvrow")
Sleep(0)

p.Tag = i
Label1.Tag = i
Label1.Text = " Click here to delete item #" & i

Return p

End Sub

Private Sub Label1_MouseClicked (EventData As MouseEvent)

'!!!!!!!!!!!!!!!!!!!!!!!!
' The exception occurs when the label in the last item (#5) is clicked
'!!!!!!!!!!!!!!!!!!!!!!!!

Dim lbl As Label = Sender
DeleteFromCustomListView(lbl.Tag)
'EventData.Consume ' <---- If this is added, the exception does NOT occur
End Sub

Private Sub DeleteFromCustomListView(id As Int)

Dim i As Int

For i = (CustomListView1.Size - 1) To 0 Step -1
Dim p As B4XView = CustomListView1.GetPanel(i)
Dim tagId As Int = p.Tag
If tagId = id Then
CustomListView1.RemoveAt(i)
Return
End If
Next

End Sub

EDIT:
1. In B4A, the exception doesn't occur
2. If 'EventData.Consume' is added to the Label's MouseClicked event sub, the exception doesn't occur

 

[josejad]

Why don't you just do:

Private Sub CustomListView1_ItemClick (Index As Int, Value As Object)
    CustomListView1.RemoveAt(Index)
End Sub

 

[walt61]

Thanks for trying @josejad , but this is just minimal demo code to show the issue. My real code is way more complex

 

[Erel]

if 'EventData.Consume' is added to the Label's MouseClicked event sub, the exception doesn't occur

This is actually the explanation for this issue.
If you don't call EventData.Consume then the event propagates to the underlying panel and when the CLV event logic fires it fails because the item was already removed. I will add a check for this case, though it is a mistake not to consume the event.

 

[walt61]

That's indeed what I assumed @Erel , and thought you might want to add that check.

 

[Erel]

and thought you might want to add that check.

Private Sub PanelClickHandler(SenderPanel As B4XView)
    Dim index As Int = SenderPanel.Tag
    If index < 0 Or index >= getSize Then
        Log("PanelClickHandler invalid index")
        Return
    End If

Done.