Why entry's Focus() method isn't working from page's constructor?

Issue

In Xamarin Forms, when I use the following code:

public SomePage()
{
    InitializeComponent();
    someEntry.Focus();
}

the code entry isn't focused by default, however, if I use the following code:

protected override void OnAppearing()
{
    base.OnAppearing();
    someEntry.Focus();
}

it works as needed (entry is focused). Why is that? Isn't codeEntry already existing and sitting at it's place, fully functional, after InitializeComponent() call? I mean, I sure can change Text property from page constructor.

Solution

In Xamarin, every control has equivalent view renderer, that is native UI element which will only be created when control is added to the native element hierarchy. In constructor, native element for entry is not yet created. However, in OnAppering, entry's corresponding native element is created so it can get the focus.

Also this seems like a bug as Xamarin is storing state and applying it when creating the native UI element. Its time to file a bug !!!

Answered By - Akash Kava