B4A Library [B4X] [XUI] AS ViewPager based on xCustomListView

Alexander Stolte · Apr 22, 2020

Hey,
thanks to @KZero for his good zPager class, i was able to extract a few things from it to make this cross platform view.

I spend a lot of time in creating views, some views i need by my self, but some views not and to create a high quality view cost a lot of time. If you want to support me, then you can do it here by Paypal or with a coffee.

This library is compatible and tested with B4A,B4I and B4J!
If you have bugs or a wish then tell me it in the comments.

Don't use autoscale in the layouts that are added to the viewpager.

On B4J use the LEFT and RIGHT keys on your keyboard to change the page.
~~On B4I you need the GestureRecognizer class. Download it down below.~~

B4j: jXUI,JavaObject,jPager,jReflection
B4a: XUi,Reflection,xCustomListView
B4i: iXUI,xCustomListView

Features

cross-platform compatible
based on a cross-platform ListView
add and remove pages
scroll to pages
a good swipe feeling
Vertical
Carousel
Lazy Loading
NEW - AllowNext and AllowBack

Horizontal and Vertical

B4A Carousel and B4I Carousel

ASViewPager
Author: Alexander Stolte
Version: 2.00

ASViewPager
- Events:
  - LazyLoadingAddContent (Parent As B4XView, Value As Object)
  - PageChange (Index As Int)
  - PageChanged (Index As Int)
  - PageChanged2 (NewIndex As Int, OldIndex As Int)
  - PageClick (Index As Int, Value As Object)
  - ReachEnd
  - ScrollChanged (Offset As Int)
  - TouchBegin
  - TouchEnd
- Fields:
  - Tag As Object
- Functions:
  - AddPage (LayoutPanel As B4XView, Value As Object) As String
  - AddPageAt (index As Int, LayoutPanel As B4XView, Value As Object) As String
    Adds an page at a special position
  - AllowBack (Allow As Boolean) As String
    If False: Prevents the user from moving to the previous page
    -The PreviousPage function will not work
    -The CurrentIndex property can be used without restrictions
  - AllowNext (Allow As Boolean) As String
    If False: Prevents the user from moving to the next page
    -The NextPage function will not work
    -The CurrentIndex property can be used without restrictions
  - Base_Resize (Width As Double, Height As Double)
  - Class_Globals As String
  - Clear As String
  - Commit As String
  - DesignerCreateView (Base As Object, Lbl As Label, Props As Map) As String
    Base type must be Object
  - getBase As B4XView
  - getCurrentIndex As Int
  - getCustomListView As b4a.example3.customlistview
  - getisScrollEnabled As Boolean
    Checks if the swipe/scroll is enabled or disabled
  - getLazyLoading As Boolean
  - getLazyLoadingExtraSize As Int
  - getLoadingPanelColor As Int
  - GetPanel (Index As Int) As B4XView
  - getSize As Int
  - GetValue (Index As Int) As Object
  - Initialize (Callback As Object, EventName As String) As String
  - IsInitialized As Boolean
    Tests whether the object has been initialized.
  - NextPage As String
  - NextPage2 As String
    Jump to next page
  - PreviousPage As String
  - PreviousPage2 As String
    jump to previous page
  - RemovePage (index As Int) As String
  - ResetLazyloadingIndex As String
  - ResetLazyLoadingPanels As String
    Removes all child views from all visible pages
    Usage:
    <code>
    xASVP_Horizontal.ResetLazyLoadingPanels
    Sleep(0)
    xASVP_Horizontal.ResetLazyloadingIndex
    xASVP_Horizontal.Commit</code>
  - Scroll2Value (Value As String) As String
    sets the current index by the value - smooth scrolls to the item
  - Scroll2Value2 (Value As String) As String
    sets the current index by the value - jumps to the item
  - setCurrentIndex (index As Int)
  - setCurrentIndex2 (index As Int)
    sets the current index - jumps to the item
  - setIgnoreLazyLoading (Ignore As Boolean) As String
    If True, the Lazy Loading event is not triggered
  - setIgnorePageChangedEvent (ignore As Boolean) As String
  - setIgnorePageChangeEvent (ignore As Boolean) As String
  - setLazyLoading (Enabled As Boolean) As String
  - setLazyLoadingExtraSize (ExtraSize As Int) As String
  - setLoadingPanelColor (Color As Int) As String
    The color of the Loading panel if Base_Resize is executed
  - setLoadingPanelHideDuration (Duration As Int) As String
  - setScroll (enabled As Boolean) As String
    B4I and B4A only
    enabled - False the scroll is deactivated
- Properties:
  - Base As B4XView [read only]
  - CurrentIndex As Int
  - CurrentIndex2
    sets the current index - jumps to the item
  - CustomListView As b4a.example3.customlistview [read only]
  - IgnoreLazyLoading
    If True, the Lazy Loading event is not triggered
  - IgnorePageChangedEvent
  - IgnorePageChangeEvent
  - isScrollEnabled As Boolean [read only]
    Checks if the swipe/scroll is enabled or disabled
  - LazyLoading As Boolean
  - LazyLoadingExtraSize As Int
  - LoadingPanelColor As Int
    The color of the Loading panel if Base_Resize is executed
  - LoadingPanelHideDuration
  - Scroll
    B4I and B4A only
    enabled - False the scroll is deactivated
  - Size As Int [read only]

Changelog

1.00
- Release
1.01
- Base_Resize is now public
- NextPage and PreviousPage Bug Fix
- setCurrentIndex Bug Fix
- PageChangeEvent Bug Fix
1.02
- B4I Bug Fixes
- NextPage and PreviousPage Bug Fix
1.03
- Resize BugFix
1.04
- B4I Page-Height BugFix
- B4I Page-Swipe BugFix
1.05
- BugFix
1.06
- Add Designer Property "Orientation" - Vertical is now supported
1.07
- BugFix getCurrentIndex
- BugFix PageChanged event is now only firing if the index is changed
- Add setIgnorePageChangedEvent Property
- Add TouchBegin Event
- Add TouchEnd Event
- BugFix PageChanged is now firing if you press on a emulator, for example the arrow up or down keys on yor keyboard
1.08
- Add Tag Property
  - https://www.b4x.com/android/forum/t...om-clv-or-any-other-container.117992/#content
- Add Clear - clears the list and sets the index to 0
- BugFix xCustomListview Top was always 0
1.09
- B4I BugFixes for Release Mode - swiping is now better
1.10
- Add AddPageAt (experimental it works for my need, if you have issuses, then tell me) - Adds an page at a special position
- Add set CurrentIndex2 - sets the current index - jumps to the item
- Better resize handling
1.11
- RemovePage Bugfixes
- B4J ScrollPane under the hood is now Transparent
- Add NextPage2 -Jump to next page
- Add PrevoiusPage2 - Jump to previous page
1.12
- [BETA] Add DesignerProperty Carousel - infinite swipe
  - On B4I Bounce Effect is disabled
- B4I ScrollView Paging is now activated, this can improve the handling
1.13
- Add PageClick Event
1.14 - read more about this update here
- [B4I only] Add Scroll - enable or disable scroll with finger
  - ASViewPager1.Scroll(False)'disable scroll with finger
1.15
- Intern Function IIF renamed to iif2
1.16
- set Scroll is now B4X - disable the swipe/scroll
  - In B4J the arrow keys (Left/Right/Up/Down) are disabled if you deactivate the swipe/scroll
- New property isScrollEnabled - checks if the swipe/scroll is enabled or disabled
- Intern Function iif2 removed and the core iif is now used
  - B4A V11+ - B4J V9.10+ - B4I V7.50+
1.18
- PageChanged Event is now firing in some cases with a delay, because of a scroll animation
- BugFix B4A setScroll - Events from other views are now no longer blocked
1.19
- BugFix on NextPage and PreviousPage
1.20 (read more about this update)
- Add Event PageChange - This event is triggered immediately after the page is changed, no delay because of animations
- Add setIgnorePageChangeEvent - prevents the PageChange event from being triggered
1.21
- BugFixes
1.22
- B4I Scroll = False BugFix
1.24
- BugFix AddPageAt is now working better on B4A
1.25
- Add Scroll2Value - sets the current index by the value - smooth scrolls to the item
  - from the AddPage and AddPageAt function the "Value" property
  - must be a string to be found
- Add Scroll2Value2 - sets the current index by the value - jump to the item
1.26 (read more about this update)
- Add Designer Property LazyLoading - activates lazy loading
  - Default: False
- Add Designer Property LazyLoadingExtraSize - How many pages to load in advance
  - Default: 5
- Add Event LazyLoadingAddContent - Add here your layout or views
1.27
- Add get and set LazyLoadingExtraSize
1.28
- Important LazyLoading improvments
1.29
- Add Commit - Triggers the LazyLoadingAddContent event
  - Call this after you have filled the list
- LazyLoading BugFixes
1.30
- Add ResetLazyloadingIndex - when you call "commit" afterwards, it is guaranteed to check if there are empty panels in the lazy loading range, if so, the LazyLoading event is triggered
1.31
- important resize improvments
- Add Loading Panel if Base_Resize is calling
- Add Designer Property LoadingPanelColor
- Add set IgnoreLazyLoading - If True, the Lazy Loading event is not triggered
- Add ResetLazyLoadingPanels - Removes all child views from all visible pages
- LazyLoading Improvments
1.32
- Carousel works now in Vertical mode
1.33
- B4I Native paging is now used
  - The paging feels smoother now
  - In debug mode, the swiping should now also run better
1.34
- B4I The GestureRecognizer is no longer needed
1.35 (read more)
- Add Designer Property BackGestureGap - Only for B4I. If you use the ViewPager on a 2nd page and still want to close the page with the swipe gesture then set the checkbox to true
  - Default: False
2.00 (read more)
- New dependency in B4J: jPager
- Removed dependency in B4J: xCustomListView
- Add GetPanel
- Add GetValue
- In B4J, the jPager is now used instead of the xCustomListView
  - Better performance
  - No more unwanted scrolling with the mouse
2.01
- BugFixes and Improvements
- Add Event PageChanged2
2.02
- Add set LoadingPanelHideDuration - The duration of how quickly the loading panel is hidden
  - Default: 500
2.03
- B4I BugFix - Prevents vertical scrolling when in horizontal mode and vice versa
2.04
- B4I BugFix - The safe area is no longer observed
  - Fixes unwanted behavior when the viewpager is in the safe area
2.05
- BugFix - by setting the set CurrentIndex or set CurrentIndex2, the PageChange and PageChanged event have been triggered multiple times
2.06
- B4A BugFix
2.07
- B4I BugFix

2.08
- B4I - PageChange event is now triggered as soon as you lift your finger when changing pages, just like in B4A
- B4J - You need jPager V1.03
- Add AllowNext
  - Default: True
  - If False: Prevents the user from moving to the next page
    - The NextPage function will not work
    - The CurrentIndex property can be used without restrictions
- Add AllowBack
  - Default: True
  - If False: Prevents the user from moving to the previous page
    - The PreviousPage function will not work
    - The CurrentIndex property can be used without restrictions

Have Fun

Alexander Stolte · Jul 28, 2021

Update

1.20
- Add Event PageChange - This event is triggered immediately after the page is changed, no delay because of animations
- Add setIgnorePageChangeEvent - prevents the PageChange event from being triggered

PageChange
The event is triggered as soon as the action to change the page is received. e.g. The user releases the viewpager and the page is changed, as soon as the user releases, this event is triggered, even before scrolling. So things can be done in advance, before the complete page is visible.
PageChanged
With the event you can be sure that the page is done scrolling and the page has changed. This may be necessary if you do some things in the background on the viewpager, for example, dynamically add another page, without that the scrolling should be affected.
setIgnorePageChangeEvent
Sometimes you don't always need an event, then just dynamically set this property to false

Alexander Stolte · Jul 28, 2021

angel_ said:
When sliding to the sides the tab line has a little delay, I liked it better before.

But this was necessary, because I had performance losses with my ASCalendarAdvanced after the page was changed, because I dynamically add more pages in the background and therefore the scrolling looked not so good.

Use the PageChange event.

Alexander Stolte · Jul 29, 2021

Update

1.21
- BugFixes

angel_ · Jul 31, 2021

So if you got it right, if I want the bar to move the same as the movement, I have to do this:

B4X:

Sub ASViewPager1_PageChange(Index As Int)
    TabStrip.ViewPager_PageChanged(Index)
End Sub

B4X:

Sub ASViewPager1_PageChanged(Index As Int)
'Code at the end of the action (end of scrolling)
End Sub

Alexander Stolte · Jul 31, 2021

angel_ said:
if I want the bar to move the same as the movement

No thats not possible.
I had tried to implement this once in an own TabStripView, since the ASViewPager did not exist yet, but I did not manage it, so I had left that.

angel_ · Aug 1, 2021

I think I explained myself wrong, this code works fine:

B4X:

Sub ASViewPager1_PageChange(Index As Int)
    TabStrip.ViewPager_PageChanged(Index)
End Sub

So I can use PageChange unless I have performance issues in transition in that case I should use PageChanged, is this interpretation correct?

Alexander Stolte · Aug 1, 2021

angel_ said:
unless I have performance issues in transition in that case I should use PageChanged, is this interpretation correct?

yes

angel_ · Aug 1, 2021

I have noticed that when you swipe with rapid movement instead of going to the next tab it goes to the last

B4X:

Sub ASViewPager1_PageChange(Index As Int)
    TabStrip.ViewPager_PageChanged(Index)
    'code...
End Sub

Alexander Stolte · Aug 1, 2021

angel_ said:
I have noticed that when you swipe with rapid movement instead of going to the next tab it goes to the last

Not every swipe the user makes should also go to the next page, if the gesture is too short or too fast, then the process stops.

angel_ · Aug 1, 2021

Alexander Stolte said:
Not every swipe the user makes should also go to the next page, if the gesture is too short or too fast, then the process stops.

With a newer device (Oneplus 8T, android 11) it is quite fluid but some lag in some demanding transition, with another older device (Oneplus one, android 10) the movement is erratic, with fast movements it jumps several tabs and goes to the last, sometimes it does not jump to the next tab as you say

wimpie3 · Aug 5, 2021

Suppose you have loaded a page from a layout, like this:

B4X:

    Dim page1 As B4XView=xui.CreatePanel("")
    page1.LoadLayout("layout_page1")
    page1.SetLayoutAnimated(0,0,0,ASViewPager1.Base.Width,ASViewPager1.Base.Height)
    ASViewPager1.addpage(page1,"")

And later on in your code, you remove that page with

B4X:

ASViewPager1.RemovePage(1)

What happens with the variables used in layout_page1? Will they still exist in the activity or will they be empty?

Alexander Stolte · Aug 5, 2021

wimpie3 said:
What happens with the variables used in layout_page1? Will they still exist in the activity or will they be empty?

No idea, best to create a new thread. What the ListView does with it I can't tell you.

Alexander Stolte · Aug 6, 2021

Update

1.22
- B4I Scroll = False BugFix

angel_ · Aug 7, 2021

Unfortunately still not working well, it takes a very long swipe almost from side to side to get it to the next tab

Alexander Stolte · Aug 7, 2021

angel_ said:
Unfortunately still not working well, it takes a very long swipe almost from side to side to get it to the next tab

B4A or B4I?
From 1.21 -> 1.22?

Alexander Stolte · Aug 7, 2021

On my old Oneplus 6 i dont have any issues.

angel_ · Aug 7, 2021

Alexander Stolte said:
B4A or B4I?
From 1.21 -> 1.22?

B4i (iPhone 6+), with 1.21 I also had problems

In release mode it seems to work fine, I'll keep testing

Alexander Stolte · Aug 7, 2021

angel_ said:
In release mode it seems to work fine

You don't publish your app in debug mode... That's why Erel has been preaching "test it in release mode first" for years. In debug mode everything runs slowly. You can scroll a list in debug mode, or let it scroll, you will see, it is extremely jerky.

Even on my Iphone 12 Pro max I have problems to get to a next page in debug mode.
I'll test it later with my old 5s and I can tell you right now, in release mode, it will run just as fast as on the 12 pro.

angel_ · Aug 8, 2021

When I do a quick swipe up (release mode, B4i) it jumps to the next tab, can it be disabled?

Alexander Stolte · Aug 8, 2021

The only thing you can do is to check if the Y value is greater than the x value.
I'll have a look at it later.

B4A Library [B4X] [XUI] AS ViewPager based on xCustomListView

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