JavaFX Java GUI Tutorial - 28 - Properties Video Lecture | JavaFX Java GUI: Learn to build Powerful Applications - Front-End Programming

alright guys welcome back and in this
video I'm going to talk to you about
properties and explain why we need to
use them in Java FX and instead of just
giving you guys a bunch of definitions
what I want to do is I actually want to
show you guys an example and it'll
demonstrate exactly why we need to use
properties so I'm going to make a new
class and I'll say that I know maybe I
have a website or some database and I
have a whole bunch of users so I'm going
to store all of their information inside
a person class so what is one of the
properties of a person well let's say
they have a first name
obviously so first name it's a string
and what is that equal to blank and if
we hit all insert we can throw in all of
our getters and setters so basically
whenever I create an object of type
person for example Bucky I can get his
first name which would be Bucky and I
could also set his first name to
whatever I wanted so in other words I
can have something like this and create
an object called Bucky and it can be a
new person and then I can just you know
make him do a whole bunch of stuff like
set his name there you go so Bucky can
set his name he can get his name I can
make another function in here called
like punch babies and just pretty much
think of it like that an object can do
things all right simple enough this is
like Java 101 so why am i explaining
this well say that I wanted to create a
program that was going to sit and wait
and see whenever the value of this
property changed then run a little bit
of code so maybe as they're typing
something in real time you want to
update the screen all right well let me
just hop back in here and all right we
got a little issue because here's the
thing I know that Bucky can do stuff for
example Bucky can get his name set his
name punch a baby eat some hot dogs
but uh what your trend asked me to do is
have first name do something so you
pretty much want to stick a listener on
first name but I mean this is not really
an object it's like part of a bigger
object so we just can't call like first
name duh whatever we want to do because
we aren't really viewing this as an
object I mean I know first name is of
type string and we do have limited
options of what we can do with a string
but we can't do cool stuff like stick a
listener directly on first name so you
know how I told you guys that Bucky was
an object but string or this first name
JavaFX doesn't really view it as one
well I lied I apologize but I had to do
it so let me clean this up and I'll
explain something really cool so
whenever we were using JavaFX what we
can do is we can actually treat these
properties as an object now one of the
main reason is that people like to do
this is because once you do that you can
add a listener on that first name for
example and another cool thing and I'm
going to show you guys how to do this in
probably the next tutorial you can
actually have two properties maybe a
first name in the last name and you can
bind them together in other words you
can attach them and then when you change
the value of the first name the last
name automatically chant changes without
any additional code needed it sounds
kind of crazy but I'm going to show you
guys an example like I said later on
don't want to overwhelm you guys so
let's figure out how to actually treat
these values as properties well if you
just make a new private variable and you
use string property as you see it
imports this package right here but
basically what we're going to do is
we're going to create it in a similar
kind of way so first name and set this
equal to new simple string property now
Street property of course is just what I
was talking about it's not a regular
string it's a property in other words
we're going to do some cool stuff to it
and this is actually just an abstract
class
and this right here simple string
property this is the class that you use
whenever you want to instantiate or in
other words create new string properties
that you can read and write to so again
this is just that abstract class the
type of object and this is for whenever
you want to create something that you
can actually read and write from or
write to whatever and it actually takes
three parameters these are easy to
understand the first one is going to be
this most of the time it just refers to
the object that contains it so this and
the second one is the name in other
words first name and the last one is the
default value so whenever we create this
it just has a default value of nothing
no name or anything like that so
actually if you hold down alt insert
we're going to do this the real lazy way
we want to throw in all of our getters
and setters all right hmm would you look
at that all right you would think that
since we had a getters and setters that
we would just have a getter and a setter
but it gave us three different methods
especially let me arrange this a little
bit easier to understand all right so
I'm actually going to comment this for
when I post it on github returns the
string whoa moly don't do that all right
so here's the thing you know how we can
pretty much store a first name in here
like Bucky just like before
well this getter in this setter act as
you would expect so what this one is
going to do is it's going to return okay
my fingers are slapping all over
keyboard return I'll just say the first
name of value ie Bucky so this is pretty
much going to be your traditional getter
it's going to return the value of that
object like you would expect and this
one of course the same set the first
name value all right so we pretty much
know what those do nothing new what the
heck is
this this is actually going to return
the object itself so not the value not
Bucky it's going to return this object
and we need that whenever we you know do
cool things like add a listener to it so
now if we hop back over in main not Java
what we can do is we can start using
this like we normally would just create
a new person so now we have an object
named Bucky and he doesn't have any name
set yet so what I'm going to do is I'm
going to take that object and I'm going
to call first name property in other
words Bucky's first name and I'm going
to add a listener to it now this is
going to be called whenever the value of
first name changes so whenever we give
them a name whenever we change his name
this code that we're going to write in
here is going to be kicked off and you
guys saw this in text before if you just
say something we clear this up V old
value and new value so it's going to
pass in three values this is the object
this is the old value so if we're
changing Bucky to Sally this is going to
be Bucky this is going to be Sally and
then we can just run a little bit of
code whatever logic that we want art so
what I'm going to actually do is just
print out some stuff on the screen so
you see what's going on
and let me just copy this little thing
right here all right so what can I print
out I'll say name change to new value so
this first one line will say whenever we
change his name it's going to say name
change to Bucky Sally whatever and for
the other one I actually just print out
this right here because I want to
demonstrate the difference between the
actual value of Bucky in the object
because that's a kind of confusing for
some people so the first thing I'm going
to do is print out the object and it's
going to look a little bit goofy but
it's Bucky first name property and by
the way in your code you typically don't
want to well I want to say for the user
interface you typically don't want to
use this a lot because this is going to
print out like essentially where the
object is in memory and what it looks
like to Java behind the scenes so the
last thing I'm going to do is print out
this get first name and Bucky get first
name so whenever you actually want to
get the user's name for example and
display to the user then you would call
you know just your basic getters and
setters so what I'm actually going to do
is this I'm going to say whenever we
click the button what I'm going to do is
just omit an event and we'll just say
Bucky sets first name equal to Porky
all right so one last time what this
program is going to do is it's going to
set up a listener on the first name so
whenever the user changes the name it's
going to emit this event right here
don't believe me
Oh hopefully it works all right so I'm
going to hit submit and check it out and
I'll explain now let me switch over to
here alright so this right here well we
saw name changed it porky that was just
the value of it get first name
that's just your typical getter like
before returns porky and this first name
property this right here is the actual
property object so it has a value of
this again like I said usually wouldn't
want to show that to the users too much
but again once we have to my voice just
cracked god that's embarrassing all
right
but anyways once we have properties then
we can do cool things like add listeners
to them and also bind them together and
I'll show you guys how to do that in the
next tutorial for now that's the basics
of it and yeah not really useful now but
wait till you learn about binding it's
going to be awesome I'll see you then