JavaFX Java GUI Tutorial - 2 - Handle User Events Video Lecture | JavaFX Java GUI: Learn to build Powerful Applications - Front-End Programming

alright guys so in this video I'm going
to be showing you how to handle user
events but before we get to that I need
to tell you a quick story because it is
kind of embarrassing and I just feel
like I need to tell someone so I was
just doing laundry few seconds ago and
whenever I do my laundry I take it and I
dump it out on my bed just because I
know it's like the right height so I
don't have to like crouch over or
anything so I take on my clean laundry
and I dumped it on my bed and then I
took the empty laundry basket and I just
put it on my head like I'm wearing some
weird helmet or I don't know why did
that no idea I just do weird things when
I'm alone so I just had this laundry
basket on my head and I'm looking at the
front window and then I look out my side
window in my neighbor who was shoveling
her porch she stops shoveling and then
we were just like looking at each other
per second and I have a laundry basket
on my head so yeah that was pretty
awkward Anna she probably thinks I'm
really weird now she didn't already but
I was pretty embarrassing anyways we're
just going to pretend that that never
happened let's go ahead and continue
with the tutorial so again what I want
to teach you guys had to do is handle
user events in other words whenever they
click this button we want to perform
some kind of action so the program is
actually interactive and it's just not a
bunch of buttons that they can look at
and not you know interact with it all so
any time that we want to actually handle
these events we need to implement an
interface called
event handler now free event handler
there are a bunch of different types of
events for example there's a button
click and there are Mouse events like
whenever moves are whenever the user
moves their mouse around there's also
touch events for touch devices whenever
they touch a screen
but of a simple button click is just an
action event so that's the kind we're
going to be talking about in this
tutorial so and I'm gonna show you guys
the method just a second but for right
now actually let me show you the method
right now now underneath start
if you hit alt insert and then choose
implement methods there's one method
that we need to implement and it's
called handles so just go ahead and
click that now handle of course is the
method that's going to be called
whenever the user clicks the button so
again whenever they click the button
that is called an event they did
something how do you want to handle it
well you write your code right here do
you want to print out a line text you
want to open up another window what do
you want to do so that's essentially how
this program is going to work now before
we just jump into handling it we need to
set one other method on your button so
on button you need to call set on action
and we're just going to pass in this and
all this says is whenever they click
this button the code to handle this is
in this class so you can actually make a
whole nother class and just pretty much
just for like handling events but since
this is a real quick tutorial I'm just
going to throw my method in the same
class so this is essentially all this is
saying whenever you are trying to handle
the button click just look in this class
for the handle method and you'll find it
simple enough so now of course we know
whenever they click the button this
method gets called so inside this method
what we can do is this now remember this
is a generic method and it's good and it
gets called whenever an event occurs but
say that we had 10 different buttons
well if we just write okay print out a
line of text we don't want every single
button click to do the same exact thing
so it's always useful to find the source
and that way it identify is pretty much
the source or which button or which
object caused this code to occur so that
way if you have 10 different buttons it
can identify the different buttons
that's all it does
so we're just going to check okay if the
source of this event was equal to this
button which is the only button that we
have on the screen then
what do you want to do well we can just
put system.out.print line and what are
we going to print whenever they click
the button just but I love it when you
touch me there all right looking good so
looking sweet so again one more time
what's going to happen if I run this you
guys are going to see and again I'm
going to click it and it's just going to
print it out right here
usually you don't really want to mix GUI
applications with console you know
little text messages because I don't
know that's the whole point of GUI
applications so you don't have to run
this crap right here but for
demonstrating it'll be fine
so then one last time any time you want
to handle user events you need to
implement this interface and then
whenever an event happens such as a
button click this method gets called and
the first thing we're going to do is
we're going to say okay what caused this
method to be called what was the source
oh it was this button so they must have
clicked it and whenever they collect it
which is just the action event I'm going
to print out this line of code and if we
have another button then we can just put
an else--if or if the source of that
equals button too then we'll just say
like you clicked button 2 and it's given
us error because we don't actually have
a button to but that's how you would
handle different buttons so uh yeah I'm
probably just gonna think about how
awkward I am and putting laundry baskets
on my head and yeah thank you guys for
watching again Morse my source code is
going to be on github link below anyways
I'll see you later