Validation

How can we validate the Textfields? Normally I would use setState() on the onPress() function but that bugs (label comes down each time) so I have to use this.[name]{} like in the example...

I want my button to be enabled when everything is filled in, but at the moment I can only validate after I click on the button.

Same here, I'd like for the textinput to not reset itself (the label coming down) when I setState.