Android Question How to handle Activity_Keypress with animation

Sub Class_Globals
    Private Root As B4XView
    Private xui As XUI
    Private LoginPage As B4XLoginPage
End Sub

Public Sub Initialize
   
End Sub

'This event will be called once, before the page becomes visible.
Private Sub B4XPage_Created (Root1 As B4XView)
    Root = Root1
    Root.LoadLayout("MainPage")
    LoginPage.Initialize
    B4XPages.AddPage("LoginPage", LoginPage)
End Sub

'You can see the list of page related events in the B4XPagesManager object. The event name is B4XPage.

Sub Button1_Click
    B4XPages.ShowPageAndRemovePreviousPages("LoginPage")
    LoginPage.AnimateFromRight
End Sub

Public Sub AnimateFromLeft
    #if B4A
    Root.Left = 100%x
    Root.SetLayoutAnimated(300, 0, 0, Root.Width, Root.Height)
    #End If
End Sub

Sub Class_Globals
    Private Root As B4XView 'ignore
    Private xui As XUI 'ignore
    Private ScrollView1 As B4XView
    Private Panel1 As B4XView
    Private MainPage As B4XMainPage
End Sub

'You can add more parameters here.
Public Sub Initialize As Object
    Return Me
End Sub

'This event will be called once, before the page becomes visible.
Private Sub B4XPage_Created (Root1 As B4XView)
    Root = Root1
    'load the layout to Root
    Root.LoadLayout("LoginPage")
    MainPage.Initialize
    B4XPages.AddPage("MainPage", MainPage)
   
    ScrollView1.ScrollViewInnerPanel.LoadLayout("LoginPage_Item")
    ScrollView1.ScrollViewContentHeight = 100%y
End Sub

Sub B4XPage_CloseRequest As ResumableSub
    B4XPages.ShowPageAndRemovePreviousPages("MainPage")
    MainPage.AnimateFromLeft
    Return True
End Sub

'You can see the list of page related events in the B4XPagesManager object. The event name is B4XPage.

Public Sub AnimateFromRight
    #if B4A
    Root.Left = -100%x
    Root.SetLayoutAnimated(300, 0, 0, Root.Width, Root.Height)
    #End If
End Sub

** Activity (main) Resume **
Page with this id already exists: mainpage!
Error occurred on line: 35 (B4XMainPage)
java.lang.RuntimeException: Object should first be initialized (B4XView).
    at anywheresoftware.b4a.AbsObjectWrapper.getObject(AbsObjectWrapper.java:67)
    at anywheresoftware.b4a.objects.B4XViewWrapper.asViewWrapper(B4XViewWrapper.java:88)
    at anywheresoftware.b4a.objects.B4XViewWrapper.setLeft(B4XViewWrapper.java:123)
    at java.lang.reflect.Method.invoke(Native Method)
    at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:732)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:348)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:255)
    at java.lang.reflect.Method.invoke(Native Method)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:144)
    at anywheresoftware.b4a.debug.Debug.delegate(Debug.java:262)
    at b4a.example.b4xloginpage._b4xpage_closerequest(b4xloginpage.java:80)
    at java.lang.reflect.Method.invoke(Native Method)
    at anywheresoftware.b4a.debug.Debug.CallSub4(Debug.java:318)
    at anywheresoftware.b4a.debug.Debug.CallSubNew(Debug.java:282)
    at java.lang.reflect.Method.invoke(Native Method)
    at anywheresoftware.b4a.keywords.Common.CallSubDebug(Common.java:1050)
    at b4a.example.b4xpagesmanager$ResumableSub_HandleCloseRequest.resume(b4xpagesmanager.java:811)
    at b4a.example.b4xpagesmanager._handlecloserequest(b4xpagesmanager.java:781)
    at b4a.example.b4xpagesmanager._activity_keypress(b4xpagesmanager.java:539)
    at b4a.example.b4xpagesdelegator._activity_keypress(b4xpagesdelegator.java:63)
    at b4a.example.main._activity_keypress(main.java:424)
    at java.lang.reflect.Method.invoke(Native Method)
    at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:732)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:351)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:255)
    at java.lang.reflect.Method.invoke(Native Method)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:144)
    at b4a.example.main$HandleKeyDelayed.runDirectly(main.java:231)
    at b4a.example.main$HandleKeyDelayed.run(main.java:228)
    at android.os.Handler.handleCallback(Handler.java:836)
    at android.os.Handler.dispatchMessage(Handler.java:103)
    at android.os.Looper.loop(Looper.java:203)
    at android.app.ActivityThread.main(ActivityThread.java:6251)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1063)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:924)
** Activity (main) Pause event (activity is not paused). **

    MainPage.Initialize
    B4XPages.AddPage("MainPage", MainPage)

B4XPages.MainPage
'or other pages:
Dim SomeOtherPage1 As SomeOtherPage = B4XPages.GetPage("some other page id")