Back-End Programming Exam > Back-End Programming Videos > Java Programming Fundamentals: For Beginners > Java Programming Tutorial - 54 - Event Handler Program
Java Programming Tutorial - 54 - Event Handler Program Video Lecture | Java Programming Fundamentals: For Beginners - Back-End Programming
FAQs on Java Programming Tutorial - 54 - Event Handler Program Video Lecture - Java Programming Fundamentals: For Beginners - Back-End Programming
| 1. What is an event handler in Java programming? |  |
Ans. An event handler in Java programming is a piece of code that is responsible for processing and responding to specific events that occur during the execution of a program. It is used to handle user actions, such as button clicks or mouse movements, and perform the necessary actions in response to those events.
| 2. How do you create an event handler in Java? | |
Ans. To create an event handler in Java, you need to follow these steps:
1. Identify the component that will generate the event, such as a button or a mouse.
2. Implement the appropriate event listener interface for that component, such as ActionListener for button clicks.
3. Override the required method(s) of the event listener interface to define the actions to be performed when the event occurs.
4. Register the event handler with the component using the component's addEventListener() method.
| 3. What is the purpose of the addEventListener() method in Java? | |
Ans. The addEventListener() method in Java is used to register an event handler with a component. It allows the component to listen for specific events and execute the associated event handler code when those events occur. This method takes the event listener object as a parameter and adds it to the list of listeners for the component.
| 4. Can you have multiple event handlers for a single component in Java? | |
Ans. Yes, it is possible to have multiple event handlers for a single component in Java. This can be achieved by registering multiple event listener objects with the component using the addEventListener() method. Each event listener will be responsible for handling a specific type of event, allowing for modular and organized event handling code.
| 5. How can you pass parameters to an event handler in Java? | |
Ans. In Java, you can pass parameters to an event handler by using anonymous inner classes or lambda expressions. With anonymous inner classes, you can declare variables outside the event handler and access them within the event handler's code. With lambda expressions, you can directly pass parameters to the event handler without the need for additional declarations. This allows for more flexibility in customizing the behavior of the event handler based on the specific event or user action.
Text Transcript from Video
what is up people welcome to your 54th
and hopefully the last tutorial in this
little three part series and before I
get started I just want to tell you guys
about one error that I did I spelled
listener run like I always do and just
change that to te NER in uh if you have
more than third grade education you
should know that but I don't so now we
can go ahead and continue with the rest
of our tutorial so pretty much in this
handling class or the class that handles
on the event what we did is we took a
string variable and we set it equal to
an empty string or a string with nothing
in it and then we say alright if they
type something in the box number one and
press Enter then we're going to say
alright we're going to change that
string to field one equals whatever you
typed in if they did it in field2 field3
or the password field that's what we're
going to do so now we all we pretty much
did is we changed that string variable
so if they type Bucky for the string
variable this pretty much changes your
string variable and now the last thing
we need to do in this class is pretty
much output it on the screen
somehow so this is the last line so
don't worry just type the j option pane
and why do we get to use this because we
imported it up here at J option pane and
what this pretty much does is pretty
much just a blank window and what we're
going to do is show message dialog make
sure I didn't spell that wrong too and
it's going to take two parameters the
first parameter it takes is null don't
worry about that has to do with
positioning and the second one it takes
is your variable you want output in that
string so now let me walk you guys
through this one last time
we imported a bunch of stuff to use
that's not important the second thing we
did is we pretty much built a window I'm
using J frame which we did in the last
tutorial you should know what how we did
that
now here just here we get to the good
stuff what you definitely need in order
to handle events is a pretty much an
event handling class that implements
action listener and we built that class
right here now once we made that class
we can create objects for that class and
we created a class or excuse me an
object named handler so anytime that you
use this object it's going to refer to
this class right here and after we built
this class and we built this object
we're going to go ahead and add that
object to each one of these items now we
gave each of these items some
functionality so before they were just
sitting there and now once you press
ENTER on them they actually do something
and what does has to do with this method
right here now inside your class that
handles events you need this method and
you need to call it action performed
this is a built-in method that has to do
with the action listener class this
method gets executed automatically
whenever an event occurs so the event
has occurred is enter so whenever they
press enter what's going to happen is
it's going to create an empty string
it's going to test what you're going to
want to change that string to and then
it's going to output it right there so
this is all the hard stuff we did it
right here so copy that and do exactly
as I did now that we made all the hard
stuff we can go ahead and just execute
it like we always do so my main thing is
called apples you can do anything you
want the first thing we're going to need
to import in the only thing so don't
worry import Java X Java X swing jframe
and this just make sure that we can use
Windows in our main method right here so
now let's go ahead and start calling our
object so let's go ahead and create a
new object called Bucky or whatever and
my class was named tuna you can name it
or whatever a year you can name your
object
whatever you want but make sure well you
should know how to do this right now
equals a new object from the class tuna
and the second line we want to put is
the closed operation liquid before so
we're going to take that object which is
pretty much the thing we just created
that window and set default there we go
closed operation didn't it's too lazy to
type at all in the argument that this is
going to take solve this crap in my way
is jframe da exit underscore on
underscore closed and like before this
just means that whenever we hit X we
want to exit the program why why they
don't do automatically I don't know but
you need to do yourself the next thing
we're going to want to do set the size
of the window and we do this by setting
the size and we're just going to set
this to something like 350 mm by 100
like what the heck was that I just had
like a piece of skin in my mouth or
something pretty disgusting by the way I
got something really disgusting to tell
you um next tutorial or five time at the
end of this tutorial but it's a
disgusting story that I heard the other
day so I'll tell you then that last
thing we need to do is set the
visibility so set visible and you learn
how to spell so and we'll just set this
to true and now let me walk you guys
through this one last time so now make
sure you don't have an errors anywhere
and go ahead and click OK okay okay okay
and hopefully this works and now here is
what we built go ahead and type Bucky
press Enter it says field 1 equals Bucky
enter text here go ahead and type um
Fred 3d field 2 equals free D uneditable
look this I'm typing I'm typing can't
edit it so go ahead and press ENTER in
that uneditable and this password on by
default if you press ENTER it's my pass
but you can go ahead and change it to
like that and then it changes to gf GDS
so I'm going to tell you guys through
this one last time how this works um if
you don't want to listen to me you can
go ahead and watch my next tutorial or
watch some videos of like dogs doing
silly things online but for those of you
guys who really want to figure out how
this works I'm going to tell you right
now this is all well let's go ahead and
just skip the good stuff right here in
order to handle events in Java you need
an event handling class in that class
needs to implement action listener and
what action listener allows you to do is
put that listener on something which
means all right I'm going to wait for an
event to happen and once it happens I'm
going to do some code and that once we
have this class we can go ahead and
create an object and why do we need to
create an object well we need to create
an object because this add action or add
action listener method it takes an
object as its argument so that's why we
needed to create an object and the
object it takes as the argument is how
it wants to handle that event so why
can't it just automatically know what
event to handle because of this class
right here well sometimes you have
different events in different classes so
that's why so now once we have this
class that handles the event and the
object though we can go ahead and add
some functionality to this so what this
method does is get performed
automatically whenever you call this
class it's kind of like a constructor
but kind of not so and what this does is
take the event is the argument which is
in this case the pressing of the enter
button what this does is says alright if
event gets source which means where the
thing occurred equals item one if it
occurred in text box item number one
then what we're going to do is set the
string equal to whatever was inside that
text box if it occurred in item to set
the string that was it what was equal to
in that text box if it occurred number
three set the string equal to
was in that text box for the same thing
and now once we set our string variable
of something depending on what was
inside that text box we're just going to
output it in the J option pane which was
that little check box I mean that little
box at the end that pretty much just
said Craig or Bucky or whatever I typed
in there so that is your tutorial on how
to handle events I'm sorry is really
long but it was also really necessary
so I guys I hope you understand pretty
much the basics of what I did we'll be
going over this a little later so if you
don't you probably figure it out but
thank you guys for watching thank you
for supporting my channel and for all
the awesome comments and some of the not
so awesome ones but again I thank all of
you guys all the people who watch my
videos so I can't wait to do next
tutorial so I'll see you then
and hopefully the last tutorial in this
little three part series and before I
get started I just want to tell you guys
about one error that I did I spelled
listener run like I always do and just
change that to te NER in uh if you have
more than third grade education you
should know that but I don't so now we
can go ahead and continue with the rest
of our tutorial so pretty much in this
handling class or the class that handles
on the event what we did is we took a
string variable and we set it equal to
an empty string or a string with nothing
in it and then we say alright if they
type something in the box number one and
press Enter then we're going to say
alright we're going to change that
string to field one equals whatever you
typed in if they did it in field2 field3
or the password field that's what we're
going to do so now we all we pretty much
did is we changed that string variable
so if they type Bucky for the string
variable this pretty much changes your
string variable and now the last thing
we need to do in this class is pretty
much output it on the screen
somehow so this is the last line so
don't worry just type the j option pane
and why do we get to use this because we
imported it up here at J option pane and
what this pretty much does is pretty
much just a blank window and what we're
going to do is show message dialog make
sure I didn't spell that wrong too and
it's going to take two parameters the
first parameter it takes is null don't
worry about that has to do with
positioning and the second one it takes
is your variable you want output in that
string so now let me walk you guys
through this one last time
we imported a bunch of stuff to use
that's not important the second thing we
did is we pretty much built a window I'm
using J frame which we did in the last
tutorial you should know what how we did
that
now here just here we get to the good
stuff what you definitely need in order
to handle events is a pretty much an
event handling class that implements
action listener and we built that class
right here now once we made that class
we can create objects for that class and
we created a class or excuse me an
object named handler so anytime that you
use this object it's going to refer to
this class right here and after we built
this class and we built this object
we're going to go ahead and add that
object to each one of these items now we
gave each of these items some
functionality so before they were just
sitting there and now once you press
ENTER on them they actually do something
and what does has to do with this method
right here now inside your class that
handles events you need this method and
you need to call it action performed
this is a built-in method that has to do
with the action listener class this
method gets executed automatically
whenever an event occurs so the event
has occurred is enter so whenever they
press enter what's going to happen is
it's going to create an empty string
it's going to test what you're going to
want to change that string to and then
it's going to output it right there so
this is all the hard stuff we did it
right here so copy that and do exactly
as I did now that we made all the hard
stuff we can go ahead and just execute
it like we always do so my main thing is
called apples you can do anything you
want the first thing we're going to need
to import in the only thing so don't
worry import Java X Java X swing jframe
and this just make sure that we can use
Windows in our main method right here so
now let's go ahead and start calling our
object so let's go ahead and create a
new object called Bucky or whatever and
my class was named tuna you can name it
or whatever a year you can name your
object
whatever you want but make sure well you
should know how to do this right now
equals a new object from the class tuna
and the second line we want to put is
the closed operation liquid before so
we're going to take that object which is
pretty much the thing we just created
that window and set default there we go
closed operation didn't it's too lazy to
type at all in the argument that this is
going to take solve this crap in my way
is jframe da exit underscore on
underscore closed and like before this
just means that whenever we hit X we
want to exit the program why why they
don't do automatically I don't know but
you need to do yourself the next thing
we're going to want to do set the size
of the window and we do this by setting
the size and we're just going to set
this to something like 350 mm by 100
like what the heck was that I just had
like a piece of skin in my mouth or
something pretty disgusting by the way I
got something really disgusting to tell
you um next tutorial or five time at the
end of this tutorial but it's a
disgusting story that I heard the other
day so I'll tell you then that last
thing we need to do is set the
visibility so set visible and you learn
how to spell so and we'll just set this
to true and now let me walk you guys
through this one last time so now make
sure you don't have an errors anywhere
and go ahead and click OK okay okay okay
and hopefully this works and now here is
what we built go ahead and type Bucky
press Enter it says field 1 equals Bucky
enter text here go ahead and type um
Fred 3d field 2 equals free D uneditable
look this I'm typing I'm typing can't
edit it so go ahead and press ENTER in
that uneditable and this password on by
default if you press ENTER it's my pass
but you can go ahead and change it to
like that and then it changes to gf GDS
so I'm going to tell you guys through
this one last time how this works um if
you don't want to listen to me you can
go ahead and watch my next tutorial or
watch some videos of like dogs doing
silly things online but for those of you
guys who really want to figure out how
this works I'm going to tell you right
now this is all well let's go ahead and
just skip the good stuff right here in
order to handle events in Java you need
an event handling class in that class
needs to implement action listener and
what action listener allows you to do is
put that listener on something which
means all right I'm going to wait for an
event to happen and once it happens I'm
going to do some code and that once we
have this class we can go ahead and
create an object and why do we need to
create an object well we need to create
an object because this add action or add
action listener method it takes an
object as its argument so that's why we
needed to create an object and the
object it takes as the argument is how
it wants to handle that event so why
can't it just automatically know what
event to handle because of this class
right here well sometimes you have
different events in different classes so
that's why so now once we have this
class that handles the event and the
object though we can go ahead and add
some functionality to this so what this
method does is get performed
automatically whenever you call this
class it's kind of like a constructor
but kind of not so and what this does is
take the event is the argument which is
in this case the pressing of the enter
button what this does is says alright if
event gets source which means where the
thing occurred equals item one if it
occurred in text box item number one
then what we're going to do is set the
string equal to whatever was inside that
text box if it occurred in item to set
the string that was it what was equal to
in that text box if it occurred number
three set the string equal to
was in that text box for the same thing
and now once we set our string variable
of something depending on what was
inside that text box we're just going to
output it in the J option pane which was
that little check box I mean that little
box at the end that pretty much just
said Craig or Bucky or whatever I typed
in there so that is your tutorial on how
to handle events I'm sorry is really
long but it was also really necessary
so I guys I hope you understand pretty
much the basics of what I did we'll be
going over this a little later so if you
don't you probably figure it out but
thank you guys for watching thank you
for supporting my channel and for all
the awesome comments and some of the not
so awesome ones but again I thank all of
you guys all the people who watch my
videos so I can't wait to do next
tutorial so I'll see you then
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Nov 25, 2024 Last updated |
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