Swift: Change centre constraint based on visible frame

Question

I've been trying to vertically centre a UILabel across all devices, both when the keyboard isn't visible and when it is visible.

I previously tried to adjust the top constraint by doing this: self.emptyStateMessageTopConstraint.constant = (self.view.frame.size.height / 2 ) - (self.emptyStateMessageHeight.constant / 2 )

This should have given me the mid point when the keyboard wasn't visible.

I did this when the keyboard was visible:

self.emptyStateMessageTopConstraint.constant = (self.view.frame.size.height - keyboardHeight) / 2 - self.emptyStateMessageHeight.constant / 2

In theory, it should have worked but it wasn't entirely vertically centre.

As you can see below, it's not centred.

I scrapped that idea and tried to centre vertically. It worked perfectly across all devices when the keyboard is not visible as seen below.

Now my issue is, how can I programmatically change the vertical constant when the keyboard is visible across all devices.

I'm struggling since the calculation I used previously can't really be used to change the vertical constant.

Answer 1

If you see the value of center constraint layout you will find it equal 0 so that determine the position of center constraint is multiplier not constant try to apply your calculations on multiplier property , but you will find multiplier property is read only so you cannot to modify on it , but there is work around for that , I hope that helpe you .