Java Reference
In-Depth Information
By changing the
scrollOffset
setting, you can control which part of the text field is visible.
To ensure that the beginning of the contents for the text field is visible, set the
scrollOffset
setting to zero. To make sure that the
end
of the contents is visible, you need to ask the
horizontalVisibility
property what the
extent
of the
BoundedRangeModel
is, to determine the
width of the range, and then set the
scrollOffset
setting to the
extent
setting, as follows:
BoundedRangeModel model = textField.getHorizontalVisibility();
int extent = model.getExtent();
textField.setScrollOffset(extent);
By changing the
horizontalAlignment
property setting, you can right-, left-, or center-justify
the contents of a
JTextField
. By default, the text alignment is left-justified. The
public void
setHorizontalAlignment(int alignment)
method takes an argument of
JTextField.LEFT
,
JTextField.CENTER
,
JTextField.RIGHT
,
JTextField.LEADING
(the default), or
JTextField.TRAILING
to specify the contents alignment. Figure 15-5 shows how the alignment setting affects the
contents.
Figure 15-5.
Text field alignments
■
Note
You can set the
document
property, inherited from
JTextComponent
, to any implementation of the
Document
interface. If you use a
StyledDocument
with a
JTextField
, the UI delegate will ignore all style
attributes. The
StyledDocument
interface is discussed in Chapter 16.
JTextComponent Operations with a JTextField
Have you ever looked for an easy way to load or save the contents of a text component? The
Swing text components provide such a method. Additionally, the Swing text components have
built-in support to access the system clipboard for cut, copy, and paste operations. These oper-
ations are possible with all
JTextComponent
subclasses. They're shown here specifically for the
JTextField
because they need a specific implementation to be truly demonstrated. You can
perform the same tasks with the
JPasswordField
,
JTextArea
,
JEditorPane
, and
JTextPane
.
Loading and Saving Content
With the
public void read(Reader in, Object description)
and
public void write(Writer
out)
methods from
JTextComponent
(both throw an
IOException
), you can easily load and save
the contents from any text component. With the
read()
method, the
description
argument is
added as a property of the
Document
data model. This allows you to retain information about
where the data came from. The following example demonstrates how to read in the contents of
file name and store it in
textComponent
. The file name is automatically retained as the description.
