JTextField is a lightweight component that allows the editingof a single line of text.
For information on and examples of using text fields,
see
is a lightweight component that allows the editing of a single line of text. For information on and examples of using text fields, see How to Use Text Fields in The Java Tutorial.
JTextField is intended to be source-compatible
with java.awt.TextField where it is reasonable to do so. This
component has capabilities not found in the java.awt.TextField
class. The superclass should be consulted for additional capabilities.
JTextField has a method to establish the string used as the
command string for the action event that gets fired. The
java.awt.TextField used the text of the field as the command
string for the ActionEvent.
JTextField will use the command
string set with the setActionCommand method if not null,
otherwise it will use the text of the field as a compatibility with
java.awt.TextField.
The method setEchoChar and getEchoChar
are not provided directly to avoid a new implementation of a
pluggable look-and-feel inadvertently exposing password characters.
To provide password-like services a separate class JPasswordField
extends JTextField to provide this service with an independently
pluggable look-and-feel.
The java.awt.TextField could be monitored for changes by adding
a TextListener for TextEvent‘s.
In the JTextComponent based
components, changes are broadcasted from the model via a
DocumentEvent to DocumentListeners.
The DocumentEvent gives
the location of the change and the kind of change if desired.
The code fragment might look something like:
DocumentListener myListener = ??;
JTextField myArea = ??;
myArea.getDocument().addDocumentListener(myListener);
The horizontal alignment of JTextField can be set to be left
justified, leading justified, centered, right justified or trailing justified.
Right/trailing justification is useful if the required size
of the field text is smaller than the size allocated to it.
This is determined by the setHorizontalAlignment
and getHorizontalAlignment methods. The default
is to be leading justified.
How the text field consumes VK_ENTER events depends
on whether the text field has any action listeners.
If so, then VK_ENTER results in the listeners
getting an ActionEvent,
and the VK_ENTER event is consumed.
This is compatible with how AWT text fields handle VK_ENTER events.
If the text field has no action listeners, then as of v 1.3 the VK_ENTER
event is not consumed. Instead, the bindings of ancestor components
are processed, which enables the default button feature of
JFC/Swing to work.
Customized fields can easily be created by extending the model and
changing the default model provided. For example, the following piece
of code will create a field that holds only upper case characters. It
will work even if text is pasted into from the clipboard or it is altered via
programmatic changes.
public class UpperCaseField extends JTextField {
public UpperCaseField(int cols) {
super(cols);
}
protected Document createDefaultModel() {
return new UpperCaseDocument();
}
static class UpperCaseDocument extends PlainDocument {
public void insertString(int offs, String str, AttributeSet a)
throws BadLocationException {
if (str == null) {
return;
}
char[] upper = str.toCharArray();
for (int i = 0; i < upper.length; i++) {
upper[i] = Character.toUpperCase(upper[i]);
}
super.insertString(offs, new String(upper), a);
}
}
}
Warning: Swing is not thread safe. For more
information see Swing’s Threading
Policy.
Warning:
Serialized objects of this class will not be compatible with
future Swing releases. The current serialization support is
appropriate for short term storage or RMI between applications running
the same version of Swing. As of 1.4, support for long term storage
of all JavaBeansTM
has been added to the java.beans package.
Please see XMLEncoder.
