How to set cursor positioned on focused Entry tag in XAML? - xaml

Question

I tried using the CursorPosition value but it doesn't appear to be working. The value is a single digit and the cursor needs to update to be in front of the digit when the value is tapped (or focused upon). Anyone know what might be the issue here?
public PaymentOccurrencesControl()
{
InitializeComponent();
PaymentNumberEntry.Focused += PaymentEntryField_Focused;
}
private void PaymentEntryField_Focused(object sender, FocusEventArgs e)
{
Device.BeginInvokeOnMainThread(() =>
{
PaymentNumberEntry.Focused += (s, e) =>
{
PaymentNumberEntry.CursorPosition = 1;
};
});
}

Answer 1

Wrap the code that sets CursorPosition in:
Device.BeginInvokeOnMainThread( () => {
…
});
This delays the cursor change until after xamarin and the phone’s OS have completed the focus action - which sets cursor position, overriding what you did.
ONLY wrap the line that sets cursor position:
public PaymentOccurrencesControl()
{
InitializeComponent();
PaymentNumberEntry.Focused += (s, e) =>
{
Device.BeginInvokeOnMainThread(() =>
{
PaymentNumberEntry.CursorPosition = 1;
};
});
}
Explanation: When the control gains focus, Android will begin executing your code after PaymentNumberEntry.Focused. It sees BeginInvoke, which tells Android "delay what's in here, until the current UI action (the control gaining focus) finishes". It queues this action:
() =>
{
PaymentNumberEntry.CursorPosition = 1;
};
This allows Android to do whatever it wants to CursorPosition (actually, to its native control's equivalent field). That's what makes the situation confusing - CursorPosition is not controlling the actual cursor position, until the next time it is given a value.
When it finishes, it returns to the MainThread loop, which looks for the next action to do. Which is your CursorPosition logic. Because your code runs last, it successfully updates Android's native cursor position.