Android Question TabStripViewPager

DawningTruth · Mar 11, 2020

My B4A was working fine. I recently upgraded.

Now it will not run TabStripPageViewer.

I get the following error message from the attached sample code:

java.lang.ClassNotFoundException: android.support.v4$view$ViewPager$OnPageChangeListener
at anywheresoftware.b4j.object.JavaObject.getCorrectClassName(JavaObject.java:288)
at anywheresoftware.b4j.object.JavaObject.createEvent(JavaObject.java:252)
at anywheresoftware.b4j.object.JavaObject.CreateEventFromUI(JavaObject.java:222)
at b4a.example.webbrowser._setuppagechangelistener(webbrowser.java:1812)
at b4a.example.webbrowser._activity_resume(webbrowser.java:1796)
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 anywheresoftware.b4a.BA.raiseEvent(BA.java:176)
at b4a.example.webbrowser.afterFirstLayout(webbrowser.java:112)
at b4a.example.webbrowser.access$000(webbrowser.java:19)
at b4a.example.webbrowser$WaitForLayout.run(webbrowser.java:84)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:101)
at android.os.Looper.loop(Looper.java:166)
at android.app.ActivityThread.main(ActivityThread.java:7523)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)

Any thoughts on what to do?

walterf25 · Mar 11, 2020

DawningTruth said:
My B4A was working fine. I recently upgraded.

Now it will not run TabStripPageViewer.

I get the following error message from the attached sample code:

java.lang.ClassNotFoundException: android.support.v4$view$ViewPager$OnPageChangeListener
at anywheresoftware.b4j.object.JavaObject.getCorrectClassName(JavaObject.java:288)
at anywheresoftware.b4j.object.JavaObject.createEvent(JavaObject.java:252)
at anywheresoftware.b4j.object.JavaObject.CreateEventFromUI(JavaObject.java:222)
at b4a.example.webbrowser._setuppagechangelistener(webbrowser.java:1812)
at b4a.example.webbrowser._activity_resume(webbrowser.java:1796)
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 anywheresoftware.b4a.BA.raiseEvent(BA.java:176)
at b4a.example.webbrowser.afterFirstLayout(webbrowser.java:112)
at b4a.example.webbrowser.access$000(webbrowser.java:19)
at b4a.example.webbrowser$WaitForLayout.run(webbrowser.java:84)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:101)
at android.os.Looper.loop(Looper.java:166)
at android.app.ActivityThread.main(ActivityThread.java:7523)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)

Any thoughts on what to do?

Open up the SDK Manager and search for ViewPager and install.

Walter

DawningTruth · Mar 12, 2020

Thx, tried the above advice and still get an error. Here is a screenshot:

Erel · Mar 12, 2020

Whenever you see an error message with android.support.* you know that you are using an unjetified library. Run Tools - Jetifier. Make sure that the library is in the additional libraries folder.

I also updated the library zip and added the androidx file so you can download the updated library: https://www.b4x.com/android/forum/threads/tabstripviewpager-better-viewpager.63975/#content

DawningTruth · Mar 12, 2020

Thx @Erel

Tried the advice provided.

It now works with the standard example project.

When I add in support for Page Change Listening, the error recurs.

B4X:

    Dim jo As JavaObject = TabStrip1
    Dim event As Object = jo.CreateEventFromUI("android.support.v4.view.ViewPager.OnPageChangeListener", "PageChangeListener", Null)
    jo.GetFieldJO("tabStrip").RunMethod("setOnPageChangeListener", Array(event))
    
    
    Sub PageChangeListener_Event (MethodName As String, Args() As Object) As Object
    'Log("Method: " & MethodName)
    
    If MethodName = "onPageSelected" Then
        Log("Method: " & MethodName)
        Dim ArgsList As List = Args
        Log ("Index: "&ArgsList.Get(0))
        'Log("Args: " & ArgsList)
    End If
    
    'Log("Current Position: "&currentPosition)
    
    Return Null
End Sub

Here is the error:

*** Service (starter) Create ***
** Service (starter) Start **
** Activity (main) Create, isFirst = true **
** Activity (main) Resume **
after
Error occurred on line: 74 (Main)
java.lang.ClassNotFoundException: android.support.v4$view$ViewPager$OnPageChangeListener
at anywheresoftware.b4j.object.JavaObject.getCorrectClassName(JavaObject.java:288)
at anywheresoftware.b4j.object.JavaObject.createEvent(JavaObject.java:252)
at anywheresoftware.b4j.object.JavaObject.CreateEventFromUI(JavaObject.java:222)
at b4a.example3.main$ResumableSub_Activity_Create.resume(main.java:661)
at anywheresoftware.b4a.shell.DebugResumableSub$DelegatableResumableSub.resumeAsUserSub(DebugResumableSub.java:48)
at java.lang.reflect.Method.invoke(Native Method)
at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:732)
at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:351)
at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:255)
at java.lang.reflect.Method.invoke(Native Method)
at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:144)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:180)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:176)
at anywheresoftware.b4a.shell.DebugResumableSub$DelegatableResumableSub.resume(DebugResumableSub.java:43)
at anywheresoftware.b4a.keywords.Common$13.run(Common.java:1705)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:101)
at android.os.Looper.loop(Looper.java:166)
at android.app.ActivityThread.main(ActivityThread.java:7523)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)
** Activity (main) Pause, UserClosed = true **

This is the line 74 referred to in the error:

B4X:

Dim event As Object = jo.CreateEventFromUI("android.support.v4.view.ViewPager.OnPageChangeListener", "PageChangeListener", Null)

I have tried to run the Jetifier but it gives me the following:

And the file is in the Additional Libraries folder:

Any other suggestions?

Erel · Mar 12, 2020

This is a different error.

Why do you need this code? You can handle the PageSelected event.

DawningTruth · Mar 12, 2020

@Erel It's absolutely necessary as it forms the core of my app. Have already spent months using this code to build a customer lazy loader for the TabStrip. I need to track swipe directions, which tab is currently active and a whole host of other actions. It is a couple of thousand lines of code.

And I'm speaking to investors next week to show them the first demo of my app. No pressure

It was based on this original code:

Custom PageChangeListener_Event Parameters

With reference to this post: https://www.b4x.com/android/forum/threads/tabstrip-access-events.80845/#post-512196 I have tried to get the sample code working on the demo TabStripViewPager app. Sub Activity_Create(FirstTime As Boolean) Activity.LoadLayout("Main")...

www.b4x.com

I went through the source on my main app again and these are the specific events I'm using:

B4X:

Sub PageChangeListener_Event (MethodName As String, Args() As Object) As Object
    
    'Handle Scroll event
    If MethodName = "onPageScrolled" Then
            
    '###### Process onPageScrolled Data Here ######
        
    End If
    
    'Handle Page Change Event
    If MethodName = "onPageSelected" Then
            
    '###### Process onPageSelected Events Here ######
            
    End If
    
    Return Null

End Sub

Erel · Mar 12, 2020

Change: android.support.v4.view.ViewPager.OnPageChangeListener

To: androidx.viewpager.widget.ViewPager.OnPageChangeListener

DawningTruth · Mar 12, 2020

Erel said:
Change: android.support.v4.view.ViewPager.OnPageChangeListener

To: androidx.viewpager.widget.ViewPager.OnPageChangeListener

Thx @Erel it worked! You are literally my hero

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Android Question TabStripViewPager

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