1
Java Programming 1
More On GUI
Lesson 5
2
Outline
More Swing GUI Components
•
JTextArea
•
JScrollPane
Introduction to Keyboard Input (without
GUI)
•
DecimalFormat
•
NumberFormat
Summary
3
Swing:
JTextArea
JTextArea
is a GUI component that is capable of displaying
many lines of text.
The statement shown here is used to construct a
JTextArea
object:
•
new JTextArea(string, rowNum, colNum)
;
•
These 3 arguments are optional
strin
g
specify the initial words to display in the
JTextArea
,
rowNum
and
colNum
specify the size of rows and columns of the
JTextArea
.
rowNum
colNum
Text/string
4
Swing: JTextArea
Methods
•
setText( string )
--
set the words
(string) in the
JTextArea
•
append( string )
--
append to the
existing text
5
How to use JTextArea
6
JTextAreaExample Class: Output
Set the
rowNum to 2
and
colNum to 2
at Line 15
Set the rowNum to 10
and
colNum to 10
at Line 15
7
Explanation: JTextAreaExample
Line 15 :
creates
JTextArea
object,
theTextArea
.
•
Display
null
, 10 rows
and
10 columns
respectively
Line 17
-
20 :
•
uses
append
method to append the contents into the
theTextArea
object
Line 22 :
display the content in a
JOptionPane
using
the
showMessageDialog
method.
•
JOptionPane.showMessageDialog(null, theTextArea,
“List of Songs",JOptionPane.INFORMATION_MESSAGE);
8
Swing:
JScrollPane
Note that:
•
The
JTextArea
does not
provide scrollbars, even if you set
the
rowNum
and
colNum
less than
the text inside the
JTextArea
.
To have the scrollbars, we need to use the
JScrollPane
object
By default,
JScrollPane
display the scrollbars only if they are
required.
Programmer can set the
horizontal
and
vertical
scrollbar for
the
JScrollPane
.
•
set
Vertical
ScrollBarPolicy(
policy
)
‡
set
Horizonta
lScrollBarPolicy(
policy
)
9
JScrollPane
Scrollbar Policies
May use the methods shown here to change
the scrollbars policies at any time. The class
JScrollPane declares the constants:
•
The scrollbar should always appear:
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS
•
The scrollbar should appear only if necessary
(the defaults) and constants:
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED
JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED
•
The scrollbar should never appear:
JScrollPane.VERTICAL_SCROLLBAR_NEVER
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER
10
How to use
JScrollPane
11
JScrollPaneExample class: Output
Vertical Scrollbar
The vertical scrollbar appear
when the JTextArea needs to
accommodate more text
12
Horizontal Scrollbar Example
The horizontal scrollbar
appear when the JTextArea
needs to accommodate more
text
theScrollbar.setHorizontalScrollBarPolicy
(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
13
Summary
Introduced two more Java Swing GUI
components
•
JTextArea
•
JScrollPane
Read in text from the command
prompt window
•
Convert the input string to integer
•
The way to use DecimalFormat and
NumberFormat
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