How to center the elements in ConstraintLayout

Question

I am using ConstraintLayout in my application to make applications layout. I am trying to a create a screen wheren one EditText and Button

Answer 1

Update:

Chain

You can now use the chain feature in packed mode as describe in Eugene's answer.

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Guideline

You can use a horizontal guideline at 50% position and add bottom and top (8dp) constraints to edittext and button: