Tabbed Chlid Page OnApearing Invoking Twice

ManjeetSingh.7994 · August 2016

Hey Guys

I'm using TabbedPage having two child inside e.g. A and B (XAML)

Now when I'm navigating to TabbedPage so, A page OnAppearing invoking two time which my default page in tab. is this the default behavior in tab or I'm doing something wrong ?

Thanks

DanP.2059 · October 2016

Has there been any movement on this? I'm experiencing the same issue. I have a TabbedPage with three child pages. At startup, OnAppearing for the first page is called twice. If I then tab to the third, then the second page, the OnAppearing for the first page is called again! The first page has a trivial amount of code in it, and the second and third page have none, so I'm sure this isn't related to my specific pages.

DanP.2059 · October 2016

As a work-around, I used the CurrentPageChanged event and a custom interface named IActivatePage on every tabbed page. It has a single method, Activate(bool), that is invoked from the TabbedPage:

    public interface IActivatePage
    {
        void Active(bool active);
    }

    public partial class MainPage  : TabbedPage
    {
        public MainPage()
        {
            InitializeComponent();
            CurrentPageChanged += MainPage_CurrentPageChanged;
        }

        private void MainPage_CurrentPageChanged(object sender, System.EventArgs e)
        {
            _lastActivePage?.Active(false);

            OnAppearing();
        }

        protected override void OnAppearing()
        {
            _lastActivePage = CurrentPage as IActivatePage;
            _lastActivePage?.Active(true);
        }

        private IActivatePage _lastActivePage;
    }

Turns out I like this solution better anyway.

ManjeetSingh.7994 · October 2016

Thanks @Dan . I will try this

RayQu · December 2016

Found the problem. In Android folder ->MainActivity if you change FormsAppCompatActivity to FormsApplicationActivity, then it works how it should work.

Maybe that is bug under FormsAppCompatActivity, the first child page onAppearing method gets invoked twice and other child pages onAppearing method gets invoked even if you don't switch to that tab.

bprasad · December 2016

Same issue @JamesMontemagno is there any solution.... i have the list view in tabbed page and i have to use appcompatactivity bcoz of custom rendering of tabbar

ZaneCampbell · December 2016

I have the same issue and I need to use appcompatactivity as well.

ThomasBurkhart · January 2017

I just stumbled over this too :-(

AndrewMcCormack · January 2017

think this bug has been fixed in the latest release.

PeterFarrer · February 2017

Andrew, do you call the latest release a pre release? If not then the bug is not fixed.

Jay_UK · February 2017

Got the same bug

PeterFarrer · February 2017

For info, best not to use OnAppearing because two instances of the page seem to be created or perhaps the first instance is disposed of, can someone report it on bugzilla please.

MiguelCervantes · March 2017

I'm having the same issue XF usgin 2.3.3.180

MiguelCervantes · March 2017

I still have the same bug with 2.3.3.193, When a tab is swiped the tab N-1 OnAppearing is also executed

nasiaM · March 2017

Ok as another work around (not sure how efficient though but it works for me)

I use a static boolean in my first tab and I initialize it as true in my constructor

On my OnAppearing method I check if my bool is true (this means it is the first time I enter the OnAppearing method)
If my flag is true do nothing just make the flag false
Then the second time I re-enter the OnAppearing my flag will be false and I will excecute any code I want.

public class MyClass:ContentPage
{
    public static bool first;
    public MyClass()
    {
        first = true;
        .
        .
        .
    }

    protected override async void OnAppearing()
    {
        if(!first)
        {
            //execute the code you want on appearing
        }
        first=false;
}

Angelru9 · August 2017

Hello, I have the same issue, my post: https://forums.xamarin.com/discussion/101000/possible-bug-tabbed-page

some solution? I'am using xamarin forms 2.3.4.247

MarcoTroncone · October 2017

Same here.

It's crazy that still with the new version 2.5 we have the same bug and no one fixed it.

This is very annoying as OnAppearing can be very important for many of us.

brux88 · December 2017

i have the same problem

TillBallendat.0434 · February 2018

y, pretty annoying bug :-(

chaosifier · February 2018

On the main TabbedPage, after you've added child pages, setting the CurrentPage property to null should fix the problem.

DaniilMikhin · February 2018

@chaosifier said:
On the main TabbedPage, after you've added child pages, setting the CurrentPage property to null should fix the problem.

Yes, it fixes the problem, thanks @chaosifier.

buchatsky · March 2018

@DaniilMikhin said:

@chaosifier said:
On the main TabbedPage, after you've added child pages, setting the CurrentPage property to null should fix the problem.

Yes, it fixes the problem, thanks @chaosifier.

Fixed, indeed. But another problem appeared: ToolbarItems of the first page are not rendered on the Toolbar

MorganTouverey-Quilling · April 2018

@buchatsky said:

@DaniilMikhin said:

@chaosifier said:
On the main TabbedPage, after you've added child pages, setting the CurrentPage property to null should fix the problem.

Yes, it fixes the problem, thanks @chaosifier.

Fixed, indeed. But another problem appeared: ToolbarItems of the first page are not rendered on the Toolbar

Yes, same problem here. Why can't we have nice things?

Edit: Found a GitHub issue for this bug : https://github.com/xamarin/Xamarin.Forms/issues/1438
It appears that the issue will be fixed in 3.0.

JSamano · July 2018

Thank you @chaosifier, fixed my problem.

nefgrixis · May 17

@chaosifier Setting the CurrentPage to null after every addition? How does the it get fixed to the correct? I just get a NullPointerException

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