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Class java.awt.TextField

java.lang.Object
   |
   +----java.awt.Component
           |
           +----java.awt.TextComponent
                   |
                   +----java.awt.TextField

public class TextField
extends TextComponent
A TextField object is a text component that allows for the editing of a single line of text.

For example, the following image depicts a frame with four text fields of varying widths. Two of these text fields display the predefined text "Hello".

Here is the code that produces these four text fields:


 TextField tf1, tf2, tf3, tf4; 
 // a blank text field
 tf1 = new TextField();
 // blank field of 20 columns
 tf2 = new TextField("", 20);
 // predefined text displayed
 tf3 = new TextField("Hello!");
 // predefined text in 30 columns
 tf4 = new TextField("Hello", 30);
 

Every time the user types a key in the text field, AWT sends two action events to the text field. The first one represents the key press and the second one, the key release. Each action event embodies the state of the system at the time that some action occurred. The properties of an action event indicate which key was pressed, what modifier keys were also pressed, and the time at which the event occurred.

Since the event is an instance of ActionEvent, the TextField class's processEvent method examines the event and passes it along to processActionEvent. The latter method redirects the event to any ActionListener objects that have registered an interest in action events generated by this text field.

See Also:
ActionEvent, processEvent, processActionEvent

Constructor Index

 o TextField()
Constructs a new text field.
 o TextField(int)
Constructs a new empty TextField with the specified number of columns.
 o TextField(String)
Constructs a new text field initialized with the specified text.
 o TextField(String, int)
Constructs a new text field initialized with the specified text to be displayed, and wide enough to hold the specified number of characters.

Method Index

 o addActionListener(ActionListener)
Adds the specified action listener to recieve action events from this text field.
 o addNotify()
Creates the TextField's peer.
 o echoCharIsSet()
Indicates whether or not this text field has a character set for echoing.
 o getColumns()
Gets the number of columns in this text field.
 o getEchoChar()
Gets the character that is to be used for echoing.
 o getMinimumSize()
Gets the minumum dimensions for this text field.
 o getMinimumSize(int)
Gets the minumum dimensions for a text field with the specified number of columns.
 o getPreferredSize()
Gets the preferred size of this text field.
 o getPreferredSize(int)
Gets the preferred size of this text field with the specified number of columns.
 o minimumSize()
Deprecated.
 o minimumSize(int)
Deprecated.
 o paramString()
Returns the parameter string representing the state of this text field.
 o preferredSize()
Deprecated.
 o preferredSize(int)
Deprecated.
 o processActionEvent(ActionEvent)
Processes action events occurring on this text field by dispatching them to any registered ActionListener objects.
 o processEvent(AWTEvent)
Processes events on this text field.
 o removeActionListener(ActionListener)
Removes the specified action listener so that it no longer receives action events from this text field.
 o setColumns(int)
Sets the number of columns in this text field.
 o setEchoChar(char)
Sets the echo character for this text field.
 o setEchoCharacter(char)
Deprecated.

Constructors

 o TextField
 public TextField()
Constructs a new text field.

 o TextField
 public TextField(String text)
Constructs a new text field initialized with the specified text.

Parameters:
text - the text to be displayed.
 o TextField
 public TextField(int columns)
Constructs a new empty TextField with the specified number of columns.

Parameters:
columns - the number of columns
 o TextField
 public TextField(String text,
                  int columns)
Constructs a new text field initialized with the specified text to be displayed, and wide enough to hold the specified number of characters.

Parameters:
text - the text to be displayed.
columns - the number of characters.

Methods

 o addNotify
 public void addNotify()
Creates the TextField's peer. The peer allows us to modify the appearance of the TextField without changing its functionality.

Overrides:
addNotify in class Component
 o getEchoChar
 public char getEchoChar()
Gets the character that is to be used for echoing.

An echo character is useful for text fields where user input should not be echoed to the screen, as in the case of a text field for entering a password.

Returns:
the echo character for this text field.
See Also:
echoCharIsSet, setEchoChar
 o setEchoChar
 public synchronized void setEchoChar(char c)
Sets the echo character for this text field.

An echo character is useful for text fields where user input should not be echoed to the screen, as in the case of a text field for entering a password.

Parameters:
c - the echo character for this text field.
See Also:
echoCharIsSet, getEchoChar
 o setEchoCharacter
 public void setEchoCharacter(char c)
Note: setEchoCharacter() is deprecated. As of JDK version 1.1, replaced by setEchoChar(char).

 o echoCharIsSet
 public boolean echoCharIsSet()
Indicates whether or not this text field has a character set for echoing.

An echo character is useful for text fields where user input should not be echoed to the screen, as in the case of a text field for entering a password.

Returns:
true if this text field has a character set for echoing; false otherwise.
See Also:
setEchoChar, getEchoChar
 o getColumns
 public int getColumns()
Gets the number of columns in this text field.

Returns:
the number of columns.
See Also:
setColumns
 o setColumns
 public synchronized void setColumns(int columns)
Sets the number of columns in this text field.

Parameters:
columns - the number of columns.
Throws: IllegalArgumentException
if the value supplied for columns is less than zero.
See Also:
getColumns
 o getPreferredSize
 public synchronized Dimension getPreferredSize(int columns)
Gets the preferred size of this text field with the specified number of columns.

Parameters:
columns - the number of columns in this text field.
Returns:
the preferred dimensions for displaying this text field.
 o preferredSize
 public synchronized Dimension preferredSize(int columns)
Note: preferredSize() is deprecated. As of JDK version 1.1, replaced by getPreferredSize(int).

 o getPreferredSize
 public Dimension getPreferredSize()
Gets the preferred size of this text field.

Returns:
the preferred dimensions for displaying this text field.
Overrides:
getPreferredSize in class Component
 o preferredSize
 public synchronized Dimension preferredSize()
Note: preferredSize() is deprecated. As of JDK version 1.1, replaced by getPreferredSize().

Overrides:
preferredSize in class Component
 o getMinimumSize
 public Dimension getMinimumSize(int columns)
Gets the minumum dimensions for a text field with the specified number of columns.

Parameters:
columns - the number of columns in this text field.
 o minimumSize
 public synchronized Dimension minimumSize(int columns)
Note: minimumSize() is deprecated. As of JDK version 1.1, replaced by getMinimumSize(int).

 o getMinimumSize
 public Dimension getMinimumSize()
Gets the minumum dimensions for this text field.

Returns:
the minimum dimensions for displaying this text field.
Overrides:
getMinimumSize in class Component
 o minimumSize
 public synchronized Dimension minimumSize()
Note: minimumSize() is deprecated. As of JDK version 1.1, replaced by getMinimumSize().

Overrides:
minimumSize in class Component
 o addActionListener
 public synchronized void addActionListener(ActionListener l)
Adds the specified action listener to recieve action events from this text field.

Parameters:
l - the action listener.
See Also:
ActionListener, removeActionListener
 o removeActionListener
 public synchronized void removeActionListener(ActionListener l)
Removes the specified action listener so that it no longer receives action events from this text field.

Parameters:
l - the action listener.
See Also:
ActionListener, addActionListener
 o processEvent
 protected void processEvent(AWTEvent e)
Processes events on this text field. If the event is an instance of ActionEvent, it invokes the processActionEvent method. Otherwise, it invokes processEvent on the superclass.

Parameters:
e - the event.
Overrides:
processEvent in class TextComponent
See Also:
ActionEvent, processActionEvent
 o processActionEvent
 protected void processActionEvent(ActionEvent e)
Processes action events occurring on this text field by dispatching them to any registered ActionListener objects.

This method is not called unless action events are enabled for this component. Action events are enabled when one of the following occurs:

Parameters:
e - the action event.
See Also:
ActionListener, addActionListener, enableEvents
 o paramString
 protected String paramString()
Returns the parameter string representing the state of this text field. This string is useful for debugging.

Returns:
the parameter string of this text field.
Overrides:
paramString in class TextComponent

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