JavaFX Java GUI Tutorial - 10 - Extract and Validate Input Video Lecture | JavaFX Java GUI: Learn to build Powerful Applications - Front-End Programming

alright ladies and gentlemen welcome
back and yes I know my voice sounds like
I just smoked 18 packs of cigarettes but
I had a cough for the last couple days
and it tore up my throughout a little
bit
whatever don't judge me alright so
anyways in this video I'm going to show
you guys how to get data from these form
fields and also how to validate them so
we already know how to make them in
other words have to display them in our
app but what happens when let's say the
user types in some username and they hit
like submit to log into your website
well we need to actually pull out the
data from here and either send off to
our database or you know update our app
in some kind of way so the first thing
I'm going to do is show you guys how to
actually get that data so it's actually
really easy by the way that was our
starting point I actually don't even
remember what was the last tutorial I
taught you but anyways our starting
point for this one is just for field and
a button that does nothing as of now
whenever you click it really simple
stuff alright so after your button what
I'm going to do is I'm going to say
whenever we click this button just
extract that and print it out in the
terminal now obviously you would want to
do something a little bit more than that
but I just want to show you guys the
concept of how that's done right now so
of course we need button set on action e
alright so what do you want to happen
whenever you click that button let me
make this a little bit prettier well
what we want to do is we just want to
print something out on the terminal so
it's just thumb out print a line and
anytime you want to extract the
information from a form element you just
put the name of the element in this word
in this case it's text field so name
input gets text to lazy it's like those
last two characters alright so now check
this out
so now what we can do is if they type
the new Boston whatever hit login we can
pull that data out if they can type you
know some number pull that data out so
that's how we actually get whatever the
user typed in now here's the thing
usually you just don't want to get
whatever value and then just start doing
whatever you want to it you want to
validate it in some kind of way by that
I mean what if you're making some kind
of like chat application or social
network app and you wanted the user to
type in their age well if they typed in
tuna fish you obviously wouldn't want to
store tuna fish in your database for age
so you'd want to actually verify that
they typed in some number first so let
me show you how to do that so instead of
just printing something out what you
usually want to do is you want to build
a couple different methods and one of
your methods is going to say verify that
the data is an integer another another
method might verify that the data they
typed in is I don't know like maybe text
only so let's just say that we were
looking for the user to enter their age
and I'll show you guys how to validate
if the data is an integer and then once
you understand that you guys are going
to understand how to do for any other
type of data you also might want to make
your own custom validation for example
if you are having user sign up and you
want them to throw in a password you
might want to make sure that it has a
capital letter a lowercase letter and
like a number and like a weird symbol so
that would be an example of a custom one
so let's just go ahead and make one
called is int and this one we're going
to have two parameters name and put
which is the entire field itself and I'm
also going to throw in the value of it
whatever they typed in so name inputs
get text now obviously we have to make
this so let me first tighten that up all
right so I want to private boo lean I'm
just going to say return true if it is
an integer return false if it is not for
example if they typed in tuna fish or
some word or like
question mark or something however if
you want to you can you know just return
the integer or whatever doesn't matter
and I named it is int so this validation
method is going to take of course a text
field and I'll just name in I don't know
input whatever and it's also going to
take the value that they typed in and
we'll just call this the message now the
easiest way in there are a bunch of
different techniques that you can use
but the easiest one I'm going to show
you guys is this what we're going to do
is we're going to throw a try-catch
statement in here and since we're
validating numbers I know that this is
going to be a number format exception
but this is going to be different if
you're like validating email addresses
or whatever so basically what we're
going to do is we're going to say int
age and hopefully they did type in a
number so what we can do is we can just
say integer parse int and inside here
you can actually type in a couple
different things you can say input get
text and of course this is going to get
whatever they typed in or you can just
say message so again this is going to
give you a double odd you know a couple
of different options depending on if you
want to look at the actual input or the
message if you want to make this really
easy you can just simplify and throw the
message in there but actually the reason
that you might want to have the input
itself is because let's say that you
wanted to UM check if it was a number
and if it wasn't you wanted to highlight
that input in red well then you would
actually need a reference to the actual
input so I will show you guys of both of
the techniques so say input get text so
what this is going to do is it's going
to get whatever they typed in and it's
going to try to convert it to an integer
now this is only going to work if they
typed in an actual number if they typed
in you know the name Bucky or something
it's going to throw an error so that's
why after this we can just say
you know just print something now in the
terminal nice for us um what can we say
we'll say like the user is age and of
course since this is going to return a
bool een will say true so hopefully if
all goes well they typed in like the
number or yeah the number 19 converts it
to age says user is 19 and returns true
no problems however if they typed in
something like I don't know their name
by accident we're just going to say
system.out.print line and the reason
that this catch occurs is because it
can't convert a name to an integer so
it's going to throw that exception so
now we can just print out some hairlike
error this out-of-the-way message and
again this message and this input get
text they're the exact same thing in
this tutorial just so you know I'm
demonstrating two different ways that
you can do it and we'll just say
something like is not a number and of
course you would want to return false
all right so check this out let's run
this bad boy and all right making sure I
got everything set up right all right so
hopefully whenever you're looking for
their age you're going to type something
like 18 click me user is 18 however if
they type like bacon that's obviously
not a number so it's going to say err
bacon is not a number and again if you
want to do something like highlight this
in red then you can do that as well so
anyways one last time what's going on is
whenever we validate that data we're
passing in the data and in this case
we're trying to convert it to an integer
now it can convert any number to an
integer no problem however when it tries
to convert some text or like an email
address to an injure it's going to throw
an error and it's going to kick off our
catch statement so there you go I'm
going to probably go take some cough
medicine
no yeah see you guys later