Java Programming Tutorial - 77 - Adapter Classes Video Lecture | Java Programming Fundamentals: For Beginners - Back-End Programming

what is going on guys welcome to your
seventy seventh Java tutorial and in
this tutorial we're gonna be learning
about something called adapter classes
now in the last tutorial when we
implemented from the interface like
Mouse listener and Mouse motion listener
we had to implement seven different
methods and those are kind of
time-consuming in sometimes you don't
always want your program to detect all
of those different methods sometimes you
only want your program to be able to
tell when the user click something
instead of drag release move you only
need one of those so what Java did is in
order to kind of save you some time
they made something called an adapter
class and what an adapter class does is
it already implements an interface and
it overrides it with a method body that
is pretty much a blank body or pretty
much a body that does nothing any we're
saying all right what's the point of
that well in that way when you inherit
from an adapter class you only have to
override the methods that you need so
it's pretty cool in the sense that you
don't have to override all of those
seven time-consuming methods like we did
before you only have to override the
ones that you're going to use in the
rest whenever you do them they just
don't do anything at all just like we
wanted them to so let me go ahead and
show you guys what I'm talking about
gonna make two variables for our program
again get all your imports right here
and the first thing they're both gonna
be private variables I'm gonna put
string in details and what this program
is gonna do is it's pretty much just
gonna say how many times well you'll see
what it does but pretty much this
details is gonna tell what's going to be
displayed in the status bar so that's
all you need to know for now
private j label and just put status bar
or whatever you named it last time and
now we got two private variables the
status bar in the details is pretty much
going to be the text that's going to
appear in your status bar so now we can
go ahead and build our constructor which
is
like gooey it's not gonna take any
parameters and for the body let's go
ahead and add a title super title since
you should always have a title get their
real name it toodle I mean why not might
as well next we can go ahead and build
our status bar which is the only thing
we're really gonna want up here in the
window so wow I really miss that up
status bar and set equal to Nu J label
and just have the text by default but
this is default it's just gonna be the
first thing that appears um after we
start doing the stuff this is gonna
disappear but now let's go ahead and add
this to the window we'll pad status bar
and of course go ahead and put like
borderlayout dot south and now there we
go
it'll appear at the bottom of the screen
if you put south we'll be going over
that later and now we need to add of
course the mouse listener just like that
add mouse listener in the parameter it
takes here is an object of the class
we're gonna build and we're gonna be
building a new class called new mouse
class and don't forget your empty
parameters for that so make sure we
didn't miss oh I know we're getting an
error because we didn't build the class
yet so let's go ahead and create a class
called Mouse class and with this Mouse
class we'll just go ahead and throw
private class Mouse class extends so we
need to build a mouse class because
that's what the parameter it took in in
our class we're gonna pretty much define
how to handle these Mouse events and we
want it to extend Mouse adapter in this
adapter class that we're extending from
this is the class that is built in a
Java already so this can be custom
whatever you named but this has to mean
Mouse adapter you have to type it just
like that
and again this adapter class is gonna
allow you to overwrite only the methods
that you need to overwrite so let's go
ahead and first
the only thing we're not gonna want to
be working with is public void mouse
clicked that's the only thing we care
about when they click we don't care when
they drag or anything else like that so
put mouse event event oh my god can I
not type I mean seriously Mouse event
event and let's go ahead and type what
do we want to happen when they click the
mouse well let's go ahead and take those
details right up here that we're gonna
have and put details set it equal to
string dot format and let's go ahead and
put something it takes two arguments but
you clicked percent D so it's gonna say
you clicked percent D and for present D
what we want to do is take that event
which is pretty much means when we click
and it put get click count just like
that BAM
already filled it in for us so it's
gonna say you clicked five six 18
whatever doesn't fill in in the end yet
so now we're gonna have to make a if
statement and we're gonna have three
parameters to finish this detail
variable so if event and here's another
kind of confusing thing that is maida
down and ever saying all right what the
heck is mated down and what's it mean
well whenever you're building a Java
program you don't really know what kind
of Mouse the user is using there's three
kind of main Mouse's there's a
one-button Mouse like on the Mac a two
button which is like old classic or a
three button Mouse in the third button
is that scroll wheel so in order to
distinguish the types of buttons that
they have you just can't assume that
they're using all your users are using
the same one so if you ever use the Mac
then how they make up for this rice
mount I mean the right mouse button is
they have something called meta which is
called the command or Apple key that
they can hold down and when they click
the mouse that simulates the right mouse
button or they can hold the Alt key and
when they click the Alt key and click
their mouse it simulates
what is it that all is the center mouse
button so that is how you can tell I
mean for now when we click the right
mouse button it's gonna work perfectly
but this pretty much is just for people
who use special like one button or two
button mouse is if you have a third
three button Mouse then this is pretty
much what does
so if meta button is down or is meta
down take your details and I know I'm
probably just going to explain it a lot
easier just by showing you what the
program is while ads at the end of that
details variable so you clicked five it
will say for example and then go ahead
and what do we want append alright there
we go
with rights mouse button so if meta is
down what does mean if they click the
right mouse button or if they hold down
that meta key is going to say with the
right mouse button else if what else do
you want the test event is alt down just
like that let's go ahead and first put
that back and details plus equals with
sensor mouse button and the cool thing
about this else by default you don't
have to test anything because you know
it's just a regular click down with left
mouse button so that's how you
distinguish between the right the center
in the left Mouse one for different
types of mice and I spelled details
wrong so and now I spelled it right so
that's all we have to do so now we have
a variable called details and it's a
string it starts with you clicked and
says a number and says with the right
mouse button either wideout by either
why don't I just put with embarrassing
and then I pretty much this is the
beginning and one of these is the end of
the string and now all we have to do is
add this to the screen so put status bar
set text and for the text we're just
going to write that details variable so
the status bar is going to set equal to
the details variable
now we can go ahead and run it and I can
show you guys what it does so says this
is default what you put that by default
and I'm gonna go ahead and click my left
mouse button now look click 1 2 3 4 5
and then if you move it and click your
center look what happens Center center
clicking with my center or in other
words my scroll wheel and then go ahead
and click here with your right and if
you go ahead and move this then it's
actually a new event so if you want to
make your things go up you've got to
stay in the same place um if you're
moving it then actually is a move event
so that's why it resets
but that's your basics of how to
distinguish between the right the center
and left and also how to use a mouse
adapter class 2 only overwrite the
methods that you want again we only over
wrote one method and we then have to
overwrite all seven for our program to
work so that's the power of a mouse
adapter class but for now thank you guys
for watching don't forget to subscribe
and I'll see you next time