OnAppearing() method is performing before calling the OnCurrentPageChanged() method - xamarin

Question

For the first time I'm restricting the onAppearing() methods in all child pages of tabbed page. I need to call the onAppearing() when I change the tab. For that, I'm using OnCurrentPageChanged() to call the onAppearing() method.
When I change the tab, I'm calling the OnCurrentPageChanged() and giving them access to run the onAppearing() functionality. onAppearing() is calling before calling the OnCurrentPageChanged().
TabbedPage code:
public partial class VendorScheduleTabbedPage : Xamarin.Forms.TabbedPage
{
public int isCount;
public VendorScheduleTabbedPage ()
{
InitializeComponent ();
Xamarin.Forms.Application.Current.Properties["dayOnAppear"] = false;
Xamarin.Forms.Application.Current.Properties["weekOnAppear"] = false;
Xamarin.Forms.Application.Current.Properties["monthOnAppear"] = false;
On<Android>().SetBarItemColor(value: Color.FromHex("#6699FF"));
On<Android>().SetBarSelectedItemColor(value: Color.Orange);
}
override protected void OnCurrentPageChanged()
{
isCount = 1;
if (this.CurrentPage.Title == "Week")
{
Xamarin.Forms.Application.Current.Properties["weekOnAppear"] = true;
}
if (this.CurrentPage.Title == "Month")
{
Xamarin.Forms.Application.Current.Properties["monthOnAppear"] = true;
}
else
{
Xamarin.Forms.Application.Current.Properties["dayOnAppear"] = true;
}
base.OnCurrentPageChanged();
}
}
}
Week Page code(child page):
public WeekSchedulePage()
{
InitializeComponent();
NavigationPage.SetHasNavigationBar(this, false);
timeSlot = new List<VendorScheduleTimeSlot>();
scheduleSlots = new List<VendorScheduleTimeSlot>();
lstVendorsData = new List<ScheduledCustomersVM>();
SortedList = new List<ScheduledCustomersVM>();
scheduledCustomersList = new List<ScheduledCustomersVM>();
rescheduledCustomersList = new List<RescheduledCustomersVM>();
ConfirmBtn.IsVisible = true;
ConfirmBtn.IsEnabled = false;
vendorDayAndHoursDataVM = new VendorDayAndHoursDataVM();
lstDaysAndHours = new List<VendorDayAndHoursDataVM>();
lstQuestionsData = new List<VendorQuestionsDataVM>();
overlay.IsVisible = false;
Alert.IsVisible = false;
presentWeekDay.Text = DateTime.Now.ToString("dddd, dd MMMM yyyy");
currentDayName = DateTime.Now.DayOfWeek.ToString();
currentDate = DateTime.Parse(presentWeekDay.Text);
}
protected override void OnAppearing()
{
var isAppear = Convert.ToBoolean(Application.Current.Properties["weekOnAppear"].ToString());
if (isAppear == true)
{
ConfirmBtn.IsVisible = true;
ConfirmBtn.IsEnabled = false;
overlay.IsVisible = false;
Alert.IsVisible = false;
Application.Current.Properties["dayOnAppear"] = true;
Application.Current.Properties["monthOnAppear"] = true;
ConfirmBtn.IsEnabled = false;
scheduledCustomersList.Clear();
rescheduledCustomersList.Clear();
presentWeekDay.Text = DateTime.Now.ToString("dddd, dd MMMM yyyy");
currentDayName = DateTime.Now.DayOfWeek.ToString();
weekwiseTimeslotClick();
base.OnAppearing();
}
}
Here I need to call OnCurrentPageChanged() method first instead of the OnApearing() method. And OnCurrentPageChanged() will give the bool value to perform the code which is in OnApearing() method.

Answer 1

In Android, onAppearing is called before OnCurrentPageChanged while in iOS OnCurrentPageChanged is called before onAppearing.
1.As jgoldberger suggested, you can call method in each Page after CurrentPageChanged:
override protected void OnCurrentPageChanged()
{
if (this.CurrentPage.Title == "Week")
{
Xamarin.Forms.Application.Current.Properties["weekOnAppear"] = true;
NavigationPage naviPage = this.Children[0] as NavigationPage;
WeekPage page = naviPage.RootPage as WeekPage;
page.test();
}else if (this.CurrentPage.Title == "Month")
{
Xamarin.Forms.Application.Current.Properties["monthOnAppear"] = true;
NavigationPage naviPage = this.Children[1] as NavigationPage;
MonthPage page = naviPage.RootPage as MonthPage;
page.test();
}
else
{
Xamarin.Forms.Application.Current.Properties["dayOnAppear"] = true;
NavigationPage naviPage = this.Children[2] as NavigationPage;
DayPage page = naviPage.RootPage as DayPage;
page.test();
}
base.OnCurrentPageChanged();
}
}
2.You can use messaging-center to notify specific page to perform some actions after CurrentPageChanged:
override protected void OnCurrentPageChanged()
{
string testStr;
if (this.CurrentPage.Title == "Week")
{
testStr = "Week";
}else if (this.CurrentPage.Title == "Month")
{
testStr = "Month";
}
else
{
testStr = "Day";
}
MessagingCenter.Send<object, string>(new object(), "CurrentPageChanged", testStr);
base.OnCurrentPageChanged();
}
And in each page:
public partial class MonthPage : ContentPage
{
public MonthPage()
{
InitializeComponent();
MessagingCenter.Subscribe<object, string>(new object(), "CurrentPageChanged", async (sender, arg) =>
{
if (arg == "Month")
{
Console.WriteLine(arg);
//do something
}
});
}
public void test() {
Console.WriteLine("test");
//do something
}
}
BTW, you should use if...else if...else instead of if...if...else in your control statement.