Java Reference
In-Depth Information
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// Fig. 12.48: TextAreaDemo.java
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// Testing TextAreaFrame.
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import
javax.swing.JFrame;
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public
class
TextAreaDemo
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{
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public
static
void
main(String[] args)
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{
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TextAreaFrame textAreaFrame =
new
TextAreaFrame();
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textAreaFrame.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE
);
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textAreaFrame.setSize(
425
,
200
);
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textAreaFrame.setVisible(
true
);
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}
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}
// end class TextAreaDemo
Fig. 12.48
|
Testing
TextAreaFrame
.
a
BoxLayout
layout manager (discussed in detail in Section 22.9) to arrange the GUI com-
ponents either horizontally or vertically.
Box
's
static
method
createHorizontalBox
cre-
ates a
Box
that arranges components from left to right in the order that they're attached.
Lines 26 and 43 create
JTextArea
s
textArea1
and
textArea2
. Line 26 uses
JText-
Area
's three-argument constructor, which takes a
String
representing the initial text and
two
int
s specifying that the
JTextArea
has
10
rows and
15
columns. Line 43 uses
JText-
Area
's two-argument constructor, specifying that the
JTextArea
has
10
rows and
15
col-
umns. Line 26 specifies that
demo
should be displayed as the default
JTextArea
content.
A
JTextArea
does not provide scrollbars if it cannot display its complete contents. So, line
27 creates a
JScrollPane
object, initializes it with
textArea1
and attaches it to container
box
. By default, horizontal and vertical scrollbars appear as necessary in a
JScrollPane
.
Lines 29-41 create
JButton
object
copyJButton
with the label
"Copy >>>"
, add
copy-
JButton
to container
box
and register the event handler for
copyJButton
's
ActionEvent
.
This button provides the external event that determines when the program should copy
the selected text in
textArea1
to
textArea2
. When the user clicks
copyJButton
, line 38
in
actionPerformed
indicates that method
getSelectedText
(inherited into
JTextArea
from
JTextComponent
) should return the selected text from
textArea1
. The user selects
text by dragging the mouse over the desired text to highlight it. Method
setText
changes
the text in
textArea2
to the string returned by
getSelectedText
.
Lines 43-45 create
textArea2
, set its editable property to
false
and add it to con-
tainer
box
. Line 47 adds
box
to the
JFrame
. Recall from Section 12.18.2 that the default
layout of a
JFrame
is a
BorderLayout
and that the
add
method by default attaches its argu-
ment to the
CENTER
of the
BorderLayout
.
