B4J Question [SOLVED] Documentation with explanation how ComboBox and ChoiceBox work?

christianjeannot · Oct 3, 2020

Hello,

is there a documentation how ComboBox and ChoiceBox work?
I saw
https://www.b4x.com/android/forum/threads/b4x-xui-views-cross-platform-views-and-dialogs.100836/
which contains an working example. From my point of view this is not enough when you want to understand it. In the Booklets I have not found it.

Best regards

--Christian

christianjeannot · Oct 3, 2020

When I search the forums and check several discussions and examples it is getting confusing.

I see sometimes

B4X:

Dim cb as ComboBox

B4X:

Dim cb as B4XView

B4X:

Dim cb as B4XComboBox

Erel · Oct 4, 2020

B4X:

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    MainForm.RootPane.LoadLayout("Layout1")
    MainForm.Show
    ComboBox1.Items.Add("Item 1")
    ComboBox1.Items.AddAll(Array("2", "3", "4"))
End Sub

Private Sub ComboBox1_ValueChanged (Value As Object)
    Log(Value)
End Sub

ComboBox and ChoiceBox are native B4J controls.
B4XComboBox is a custom view that is included in XUI Views. If you are interested in cross platform development then B4XComboBox is the best choice. Under the hood it is a regular ComboBox in B4J.

All native views can be cast to B4XView (and vice versa). More information here: [B4X] [XUI] Cross platform & native UI library

christianjeannot · Oct 4, 2020

Hello Erel,

thank you for your information and example code.

I have a problem of understanding. Maybe also less experience.

I have checked the link. You say

The purpose of XUI library is to make it easier to share code between B4A, B4J and B4i projects.
It is an important new library and I expect that all B4X developers who target more than a single platform will use it at some point.

Two main concepts:
- XUI libraries API is the same between all three libraries.
- It is very simple to switch between the XUI objects and the native objects when needed.

And here is my problem of understanding.

When I use

B4X:

Private ComboBox1 As ComboBox

I can use

B4X:

ComboBox1.Items.Add("Item 1")

When I use

B4X:

Private ComboBox1 As B4XComboBox

this is not possible. The method

B4X:

Items.Add("Item 1")

is not there.

I want to create an App which runs on Android, iOS and Desktop. If ComboBox is for B4J my idea/undestanding was that I should use B4XComboBox but how can I add items when .Items.Add is not available?

Erel · Oct 4, 2020

B4XComboBox usage is demonstrated here: https://www.b4x.com/android/forum/t...ss-platform-views-and-dialogs.100836/#content

B4X:

Dim Items As List
Items.Initialize
For i = 1 To 10
    Items.Add($"Item #${i}"$)
Next
B4XComboBox1.SetItems(Items)

christianjeannot · Oct 4, 2020

Hello Erel,

thank you for the code and the information. I will check it.

B4J Question [SOLVED] Documentation with explanation how ComboBox and ChoiceBox work?

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