B4J Question How to trigger click event?

Chris Guanzon · Jul 11, 2025

Hello,

Could anyone please help me figure out how to make this click event work? It's not triggering when I click it, and I’m not sure what I’m doing wrong. What I’m trying to achieve is to detect which button or view was clicked.

Thank you so much!

LucaMs · Jul 11, 2025

B4X:

'Private Sub fbv_Click(view As B4XView)
Private Sub btn_Click
    Dim b As Button = Sender
    Log("Clicked: " & b.Text)
End Sub

The Buttons you added are not part of your class (they were not declared in it).

LucaMs · Jul 11, 2025

You can do something similar to the project I attach (note that some Subs of the B4X Custom View template are different from the ones you wrote).

Cableguy · Jul 11, 2025

I think yor issue is related to the way you are attaching the Clicked event...
You may try to explore the following:

which seems to be much more suited to what you want.

stevel05 · Jul 11, 2025

If your aim is just to get the click event in the Main module and do not need to know in the Justflexbox class that it has been clicked, you do not need to capture the click event in the JustFlexbox Class and pass it back to the main module.

As you are creating the button in the Main module, it will automatically get the default events which will be called in the module in which the views are created, so you just need to add the sub in the Main module:

B4X:

Private Sub btn_Click
    Dim btn As B4XView = Sender
    Log(btn.Text)
End Sub

Cableguy · Jul 11, 2025

he is creating an array of B4XViews (passed from the FlexBox initialize method) in the class, so the click method is triggered in that class.
Since he is creating them dynamically, he need to bound the click events by code.
Sender is only useful if the views are created using the Visual Designer, in which the views event name can be set!

Cableguy · Jul 11, 2025

stevel05 said:
As you are creating the button in the Main module, it will automatically get the default events which will be called in the module in which the views are created, so you just need to add the sub in the Main module:

that is not the view he is trying to get the click event to trigger!

stevel05 · Jul 11, 2025

B4X:

Public Sub AddFlexChild(v As B4XView, width As Int, height As Int)
    nView = v
    mBase.AddView(nView, 0, 0, width, height)
    Children.Add(nView)

    ' Attach click event if callback exists
    If xui.SubExists(mCallBack, mEventName & "_Click", 1) Then
        nView.Tag = "justflexbox_child"
        #If B4J
        Dim jo As JavaObject = nView
        jo.RunMethod("setOnMouseClicked", Array(jo.CreateEvent("javafx.event.EventHandler", "FlexChild_Clicked", True)))
        #End If
    End If

    LayoutChildren
End Sub

v As B4xview is the button created in Main and passed to the JustFlexbox Class, the event is already attached at this point, the method only creates an array of the views. Check my example project.

Cableguy · Jul 11, 2025

stevel05 said:
B4X:

Public Sub AddFlexChild(v As B4XView, width As Int, height As Int) nView = v mBase.AddView(nView, 0, 0, width, height) Children.Add(nView) ' Attach click event if callback exists If xui.SubExists(mCallBack, mEventName & "_Click", 1) Then nView.Tag = "justflexbox_child" #If B4J Dim jo As JavaObject = nView jo.RunMethod("setOnMouseClicked", Array(jo.CreateEvent("javafx.event.EventHandler", "FlexChild_Clicked", True))) #End If End If LayoutChildren End Sub

v As B4xview is the button created in Main and passed to the JustFlexbox Class, the event is already attached at this point, the method only creates an array of the views. Check my example project.

You are Right, as usual....
I didn't see this because i was concentrated in the Flex class, and it is ilogic for me to the buttons be created outside the class... but it's the OP choice...

stevel05 · Jul 11, 2025

Cableguy said:
Sender is only useful if the views are created using the Visual Designer, in which the views event name can be set!

Not so, the buttons are created in Main as

B4X:

Dim btn As Button
btn.Initialize("btn")

The Event Name is "btn" and Sender will return the button that was clicked.

stevel05 · Jul 11, 2025

Cableguy said:
it is ilogic for me to the buttons be created outside the class

I have used exactly this 'trick' in the past, to avoid having to capture and pass back events in helper classes.

stevel05 · Jul 11, 2025

For completeness, if you did want to know that the button had been clicked in a helper class, you can use an event filter as opposed to replacing the click event, that way (as long as you don't consume the event), both events will be triggered. The filtered event first.

LucaMs · Jul 11, 2025

stevel05 said:
B4X:

Public Sub AddFlexChild(v As B4XView, width As Int, height As Int) nView = v mBase.AddView(nView, 0, 0, width, height) Children.Add(nView) ' Attach click event if callback exists If xui.SubExists(mCallBack, mEventName & "_Click", 1) Then nView.Tag = "justflexbox_child" #If B4J Dim jo As JavaObject = nView jo.RunMethod("setOnMouseClicked", Array(jo.CreateEvent("javafx.event.EventHandler", "FlexChild_Clicked", True))) #End If End If LayoutChildren End Sub

v As B4xview is the button created in Main and passed to the JustFlexbox Class, the event is already attached at this point, the method only creates an array of the views. Check my example project.

(I'm "half asleep" and have a nasty headache, so I might be about to write nonsense).

That's interesting. That's a great solution (well done Steve), but thinking about it... it's limited to the button click event and certainly isn't cross-platform. What if you wanted to create a B4X Custom View that's a container for different types of Views, say native ones, and trigger different events?

Really hard.

stevel05 · Jul 11, 2025

Custom views are different, the views used need to be created within the custom view itself and events on the contained views need to be handled in the Custom View class and passed to the parent module as required. Otherwise it wouldn't be a custom view but a container.

LucaMs · Jul 11, 2025

stevel05 said:
Custom views are different, the views used need to be created within the custom view itself and events on the contained views need to be handled in the Custom View class and passed to the parent module as required. Otherwise it wouldn't be a custom view but a container.

What @Chris Guanzon is trying to do is precisely a custom view, a container to which views can be added at runtime.

stevel05 · Jul 11, 2025

LucaMs said:
What @Chris Guanzon is trying to do is precisely a custom view.

True, but it's a Custom View for the flexbox, and the buttons passed are it's children. As would be with a Pane or similar. An edge case.

For your scenario, it would probably be easier to do something similar.

PaulMeuris · Jul 12, 2025

And how about this...
Use the button tag as an index...
The B4J subroutine is called: btn_MouseClicked...

B4X:

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
    Private xui As XUI
    Private Button1 As B4XView
    Private Pane1 As Pane
    Private fbv As JustFlexbox
    Private index As Int = 0
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    MainForm.RootPane.LoadLayout("Layout1")
    MainForm.Show
   
    ' Initialize JustFlexbox with Pane1 as base
    fbv.Initialize(Pane1, "fbv")
   
    fbv.FlexDirection = "row"
    fbv.Wrap = True
    fbv.GapX = 10dip
    fbv.GapY = 10dip
    fbv.JustifyContent = "center"
    fbv.AlignItems = "center"
   
    ' Add buttons dynamically
    For i = 1 To 12
        Dim btn As Button
        btn.Initialize("btn")
        btn.Text = "Btn " & i
        btn.Tag = index
        Dim w As Int = 80 + Rnd(0, 40)
        Dim h As Int = 50
        fbv.AddFlexChild(btn, w, h)
        index = index + 1
    Next
   
    For i = 1 To 8
        Dim btn As Button
        btn.Initialize("btn")
        btn.Text = "Btn " & i
        btn.Tag = index
        fbv.AddFlexChild(btn, 80dip, 50dip)
        index = index + 1
    Next
End Sub

Private Sub fbv_Click(view As B4XView)
    Log("Clicked: " & view.Text)
End Sub

Private Sub btn_MouseClicked(EventData As MouseEvent)
    Dim btn As Button = Sender
    Log("mouse clicked " & btn.Text & " tag = " & btn.tag)
    Log("view text " & fbv.GetBase.GetView(btn.Tag).Text)
End Sub

Or if you are interested in the width of the button...

B4X:

Log("view width " & fbv.GetBase.GetView(btn.Tag).Width)

stevel05 · Jul 13, 2025

Yes, all of the default events are available. Although in this case, it would be better to add the index in the JustFlexbox LayoutChildren method. If the views are later sorted, filtered or added / deleted, the index will be maintained correctly.

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