This thread is a good example of how not to ask a question.
The correct way is:
1. This is my code:
Sub Class_Globals
Private Root As B4XView
Private xui As XUI
End Sub
Public Sub Initialize
' B4XPages.GetManager.LogEvents = True
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")
End Sub
'You can see the list of page related events in the B4XPagesManager object. The event name is B4XPage.
Private Sub Button1_Click
' xui.MsgboxAsync("Hello world!", "B4X")
' StartActivity.LoadLayout("LeftSide")
' Activity.LoadLayout("LeftSide")
' B4XPages.ShowPage("LeftSide")
B4XPages.ShowPage("LeftSide")
End Sub
When the button is clicked the app crashes with these logs:
*** Service (starter) Create ***
** Service (starter) Start **
** Activity (main) Create (first time) **
Call B4XPages.GetManager.LogEvents = True to enable logging B4XPages events.
** Activity (main) Resume **
Error: page id not found: LeftSide
Ids: (ArrayList) [mainpage]
Error occurred on line: 38 (B4XOrderedMap)
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Object.equals(java.lang.Object)' on a null object reference
at b4a.example.b4xpagesmanager._showpage(b4xpagesmanager.java:421)
at b4a.example.b4xpages._showpage(b4xpages.java:29)
at b4a.example.b4xmainpage._button1_click(b4xmainpage.java:66)
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:157)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:201)
at anywheresoftware.b4a.objects.ViewWrapper$1.onClick(ViewWrapper.java:80)
at android.view.View.performClick(View.java:8033)
at android.view.View.performClickInternal(View.java:8010)
at android.view.View.-$$Nest$mperformClickInternal(Unknown Source:0)
at android.view.View$PerformClick.run(View.java:31336)
at android.os.Handler.handleCallback(Handler.java:991)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loopOnce(Looper.java:232)
at android.os.Looper.loop(Looper.java:317)
at android.app.ActivityThread.main(ActivityThread.java:8787)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:591)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:871)
Answer: don't miss this line: Error: page id not found: LeftSide
You forgot to add the page with B4XPages.AddPage. See the example:
https://www.b4x.com/android/forum/t...k-for-managing-multiple-pages.118901/#content