AWT Choice and List in Java with Examples
Table of Contents
a) Introduction to Choice
b) Constructor of Choice
c) Example with source code and output
d) Introduction to List
e) Constructor of List
f) Example with source code and output
***************
Choice:
In AWT, Choice is used
to create a drop down list in an application. It means that is used to the
select the item from the list of items in the combo box. But only we can select
one item at a time in combo box. In SWING we use JComboBox to create the drop
down menu. In AWT Choice, scroll bar is also automatically added when there are
more than eight (8) items in the list. It generates the ItemEvent every time
when an item is selected from the choice.
The constructor of
Choice class is Choice(). It has only one
constructor.
Methods that is used to
create the Choice class are:
add(String)
or addItem(String)
– both of the methods is used to add the item in the list.
getSelectedIndex() –
this method is used to get the selected index of the item. It returns the
integer value.
getSelectedItem()
– this method is used to get the item selected of the drop down list. It
returns the object type.
Let go through the
example of Choice with source code and its output:
Source Code:
Source Code:
/*
* To change this license header, choose
License Headers in Project Properties.
* To change this template file, choose Tools |
Templates
* and open the template in the editor.
*/
package AWTComponents;
/**
*
* @author AnkitPC
*/
/*
Create an AWT GUI with a dropdown
list and a textfield. When item in the list is selected
,display it in the textfield
*/
import java.awt.*;
import java.awt.event.*;
public class ChoiceDemo extends
WindowAdapter implements ItemListener {
Frame f;
TextField t;
Choice c;
// constructor
ChoiceDemo(){
f=new Frame("Choice Demo");
// set size
f.setSize(400,300);
// set layout
f.setLayout(new FlowLayout());
String
items[]={"a","b","c","d","e","f","g","h","i"};
t=new TextField(15);
c=new Choice();
// adding items to the list
for(int i=0;i<items.length;i++){
c.addItem(items[i]);
}
// registering the item event
c.addItemListener(this);
// registering the window event
f.addWindowListener(this);
// add components to the frame
f.add(t);
f.add(c);
f.setVisible(true);
}
// main method
public static void main(String[] args) {
// call constructor
new ChoiceDemo();
}
// overriding the methods of WindowAdapter and ItemListener
// to close the frame because it is AWT frame
public void windowClosing(WindowEvent e){
f.dispose();
}
// performing action to display the output to text field.
public void itemStateChanged(ItemEvent e){
String
s=c.getSelectedItem().toString();
t.setText(s);
}
}
Output:
The image below is the
initial output of the program.
Now you can see I have
added 9 items in the list. So scroll bar is appeared to the list.
See the video output
also.
List:
List is the class in
AWT. List is used to display the multiple items on the display as choice. Unlike
choice, we can select more than one item from the list. It means multiple
selection of item also can also be done. Unlike Swing JList, we should not add
scrollbar manually here. Scroll bar is also automatically added after four (4)
items. It also generates the ItemEvent whenever the item is selected from the
list.
There are three
constructors of the List class, they are;
a) List() – This is the
first constructor of the List class. It displays the scroll bar visible after
four (4) items in the list.
b) List(int visibleRows) –
This is the second constructor of List class. In this constructor we can pass
the integer value to set the number of visible rows in the list.
c) List(int visibleRows, boolean
isMultipleSelection) – This is the third constructor. As you can see, we should
pass two values in this constructor. The first parameter takes the integer
value i.e. number of visible rows in the list and the second parameter takes
the boolean value i.e. either ‘true’ or ‘false’. True represents multiple
selection and False represents single selection.
Let us see the example
of List with source code and output;
Source Code:
/*
* To change this license header, choose
License Headers in Project Properties.
* To change this template file, choose Tools |
Templates
* and open the template in the editor.
*/
package AWTComponents;
/**
*
* @author AnkitPC
*/
import java.awt.*;
import java.awt.event.*;
public class ListDemo extends
WindowAdapter implements ItemListener {
Frame f;
List l;
TextField t;
// constructor
ListDemo(){
f=new Frame("List Demo");
// set size of frame
f.setSize(400,300);
// set layout
f.setLayout(new FlowLayout());
// register window event
f.addWindowListener(this);
t=new TextField(15);
// using second constructor
l=new List(3,true);
// registering the item event
l.addItemListener(this);
String
items[]={"a","b","c","d","e","f","g","h","i"};
// add items to the list
for(int i=0;i<items.length;i++){
l.add(items[i]);
}
// add components to the frame
f.add(t);
f.add(l);
f.setVisible(true);
}
// main method
public static void main(String[] args) {
// call constructor
new ListDemo();
}
// overrind the WindowAdapter class and ItemListener interface
// closing the window
public void windowClosing(WindowEvent e){
f.dispose();
}
// performing the action
public void itemStateChanged(ItemEvent e){
String s[]=l.getSelectedItems();
String result="";
for(String ss:s){
result+=ss;
}
t.setText(result);
}
}
Output:
The image below is the initial output of the
program.
As you can see the multiple selection of the items
can be done because I have passed ‘true’ value for isMultipleSlection. You can
try giving it value to false in you own.
Also you can watch the video output.
*****************
0 Comments