KeyEvent

Overview

Package

Class

Tree

Deprecated

Index

Help

Codase Click

search sample or example code,

search definition,

search google

PREV CLASS NEXT CLASS

FRAMES NO FRAMES

SUMMARY: NESTED | FIELD | CONSTR | METHOD

DETAIL: FIELD | CONSTR | METHOD

java.awt.event
Class KeyEvent

java.lang.Object   
  java.util.EventObject   
      java.awt.AWTEvent   
          java.awt.event.ComponentEvent   
              java.awt.event.InputEvent   
                  java.awt.event.KeyEvent

All Implemented Interfaces:: Serializable

Direct Known Subclasses:: MenuKeyEvent

public class KeyEvent
extends InputEvent
extends InputEvent

An event which indicates that a keystroke occurred in a component.

This low-level event is generated by a component object (such as a text field) when a key is pressed, released, or typed. The event is passed to every KeyListener or KeyAdapter object which registered to receive such events using the component's addKeyListener method. (KeyAdapter objects implement the KeyListener interface.) Each such listener object gets this KeyEvent when the event occurs.

"Key typed" events are higher-level and generally do not depend on the platform or keyboard layout. They are generated when a Unicode character is entered, and are the preferred way to find out about character input. In the simplest case, a key typed event is produced by a single key press (e.g., 'a'). Often, however, characters are produced by series of key presses (e.g., 'shift' + 'a'), and the mapping from key pressed events to key typed events may be many-to-one or many-to-many. Key releases are not usually necessary to generate a key typed event, but there are some cases where the key typed event is not generated until a key is released (e.g., entering ASCII sequences via the Alt-Numpad method in Windows). No key typed events are generated for keys that don't generate Unicode characters (e.g., action keys, modifier keys, etc.).

The getKeyChar method always returns a valid Unicode character or CHAR_UNDEFINED. Character input is reported by KEY_TYPED events: KEY_PRESSED and KEY_RELEASED events are not necessarily associated with character input. Therefore, the result of the getKeyChar method is guaranteed to be meaningful only for KEY_TYPED events.

For key pressed and key released events, the getKeyCode method returns the event's keyCode. For key typed events, the getKeyCode method always returns VK_UNDEFINED.

"Key pressed" and "key released" events are lower-level and depend on the platform and keyboard layout. They are generated whenever a key is pressed or released, and are the only way to find out about keys that don't generate character input (e.g., action keys, modifier keys, etc.). The key being pressed or released is indicated by the getKeyCode method, which returns a virtual key code.

Virtual key codes are used to report which keyboard key has been pressed, rather than a character generated by the combination of one or more keystrokes (such as "A", which comes from shift and "a").

For example, pressing the Shift key will cause a KEY_PRESSED event with a VK_SHIFT keyCode, while pressing the 'a' key will result in a VK_A keyCode. After the 'a' key is released, a KEY_RELEASED event will be fired with VK_A. Separately, a KEY_TYPED event with a keyChar value of 'A' is generated.

Notes:

Key combinations which do not result in Unicode characters, such as action keys like F1 and the HELP key, do not generate KEY_TYPED events.
Not all keyboards or systems are capable of generating all virtual key codes. No attempt is made in Java to generate these keys artificially.
Virtual key codes do not identify a physical key: they depend on the platform and keyboard layout. For example, the key that generates VK_Q when using a U.S. keyboard layout will generate VK_A when using a French keyboard layout.
Not all characters have a keycode associated with them. For example, there is no keycode for the question mark because there is no keyboard for which it appears on the primary layer.
In order to support the platform-independent handling of action keys, the Java platform uses a few additional virtual key constants for functions that would otherwise have to be recognized by interpreting virtual key codes and modifiers. For example, for Japanese Windows keyboards, VK_ALL_CANDIDATES is returned instead of VK_CONVERT with the ALT modifier.

WARNING: Aside from those keys that are defined by the Java language (VK_ENTER, VK_BACK_SPACE, and VK_TAB), do not rely on the values of the VK_ constants. Sun reserves the right to change these values as needed to accomodate a wider range of keyboards in the future.

Since:: 1.1
See Also:: KeyAdapter , KeyListener , Tutorial: Writing a Key Listener, Reference: The Java Class Libraries (update file), Serialized Form

Field Summary
`static char`	`CHAR_UNDEFINED` KEY_PRESSED and KEY_RELEASED events which do not map to a valid Unicode character use this for the keyChar value.
`static int`	`KEY_FIRST` The first number in the range of ids used for key events.
`static int`	`KEY_LAST` The last number in the range of ids used for key events.
`static int`	`KEY_LOCATION_LEFT` A constant indicating that the key pressed or released is in the left key location (there is more than one possible location for this key).
`static int`	`KEY_LOCATION_NUMPAD` A constant indicating that the key event originated on the numeric keypad or with a virtual key corresponding to the numeric keypad.
`static int`	`KEY_LOCATION_RIGHT` A constant indicating that the key pressed or released is in the right key location (there is more than one possible location for this key).
`static int`	`KEY_LOCATION_STANDARD` A constant indicating that the key pressed or released is not distinguished as the left or right version of a key, and did not originate on the numeric keypad (or did not originate with a virtual key corresponding to the numeric keypad).
`static int`	`KEY_LOCATION_UNKNOWN` A constant indicating that the keyLocation is indeterminate or not relevant.
`static int`	`KEY_PRESSED` The "key pressed" event.
`static int`	`KEY_RELEASED` The "key released" event.
`static int`	`KEY_TYPED` The "key typed" event.
`static int`	`VK_0` VK_0 thru VK_9 are the same as ASCII '0' thru '9' (0x30 - 0x39)
`static int`	`VK_1`
`static int`	`VK_2`
`static int`	`VK_3`
`static int`	`VK_4`
`static int`	`VK_5`
`static int`	`VK_6`
`static int`	`VK_7`
`static int`	`VK_8`
`static int`	`VK_9`
`static int`	`VK_A` VK_A thru VK_Z are the same as ASCII 'A' thru 'Z' (0x41 - 0x5A)
`static int`	`VK_ACCEPT` Constant for the Accept or Commit function key.
`static int`	`VK_ADD`
`static int`	`VK_AGAIN`
`static int`	`VK_ALL_CANDIDATES` Constant for the All Candidates function key.
`static int`	`VK_ALPHANUMERIC` Constant for the Alphanumeric function key.
`static int`	`VK_ALT`
`static int`	`VK_ALT_GRAPH` Constant for the AltGraph function key.
`static int`	`VK_AMPERSAND`
`static int`	`VK_ASTERISK`
`static int`	`VK_AT` Constant for the "@" key.
`static int`	`VK_B`
`static int`	`VK_BACK_QUOTE`
`static int`	`VK_BACK_SLASH` Constant for the back slash key, "\"
`static int`	`VK_BACK_SPACE`
`static int`	`VK_BEGIN` Constant for the Begin key.
`static int`	`VK_BRACELEFT`
`static int`	`VK_BRACERIGHT`
`static int`	`VK_C`
`static int`	`VK_CANCEL`
`static int`	`VK_CAPS_LOCK`
`static int`	`VK_CIRCUMFLEX` Constant for the "^" key.
`static int`	`VK_CLEAR`
`static int`	`VK_CLOSE_BRACKET` Constant for the close bracket key, "]"
`static int`	`VK_CODE_INPUT` Constant for the Code Input function key.
`static int`	`VK_COLON` Constant for the ":" key.
`static int`	`VK_COMMA` Constant for the comma key, ","
`static int`	`VK_COMPOSE` Constant for the Compose function key.
`static int`	`VK_CONTEXT_MENU` Constant for the Microsoft Windows Context Menu key.
`static int`	`VK_CONTROL`
`static int`	`VK_CONVERT` Constant for the Convert function key.
`static int`	`VK_COPY`
`static int`	`VK_CUT`
`static int`	`VK_D`
`static int`	`VK_DEAD_ABOVEDOT`
`static int`	`VK_DEAD_ABOVERING`
`static int`	`VK_DEAD_ACUTE`
`static int`	`VK_DEAD_BREVE`
`static int`	`VK_DEAD_CARON`
`static int`	`VK_DEAD_CEDILLA`
`static int`	`VK_DEAD_CIRCUMFLEX`
`static int`	`VK_DEAD_DIAERESIS`
`static int`	`VK_DEAD_DOUBLEACUTE`
`static int`	`VK_DEAD_GRAVE`
`static int`	`VK_DEAD_IOTA`
`static int`	`VK_DEAD_MACRON`
`static int`	`VK_DEAD_OGONEK`
`static int`	`VK_DEAD_SEMIVOICED_SOUND`
`static int`	`VK_DEAD_TILDE`
`static int`	`VK_DEAD_VOICED_SOUND`
`static int`	`VK_DECIMAL`
`static int`	`VK_DELETE`
`static int`	`VK_DIVIDE`
`static int`	`VK_DOLLAR` Constant for the "$" key.
`static int`	`VK_DOWN` Constant for the non-numpad down arrow key.
`static int`	`VK_E`
`static int`	`VK_END`
`static int`	`VK_ENTER`
`static int`	`VK_EQUALS` Constant for the equals key, "="
`static int`	`VK_ESCAPE`
`static int`	`VK_EURO_SIGN` Constant for the Euro currency sign key.
`static int`	`VK_EXCLAMATION_MARK` Constant for the "!" key.
`static int`	`VK_F`
`static int`	`VK_F1` Constant for the F1 function key.
`static int`	`VK_F10` Constant for the F10 function key.
`static int`	`VK_F11` Constant for the F11 function key.
`static int`	`VK_F12` Constant for the F12 function key.
`static int`	`VK_F13` Constant for the F13 function key.
`static int`	`VK_F14` Constant for the F14 function key.
`static int`	`VK_F15` Constant for the F15 function key.
`static int`	`VK_F16` Constant for the F16 function key.
`static int`	`VK_F17` Constant for the F17 function key.
`static int`	`VK_F18` Constant for the F18 function key.
`static int`	`VK_F19` Constant for the F19 function key.
`static int`	`VK_F2` Constant for the F2 function key.
`static int`	`VK_F20` Constant for the F20 function key.
`static int`	`VK_F21` Constant for the F21 function key.
`static int`	`VK_F22` Constant for the F22 function key.
`static int`	`VK_F23` Constant for the F23 function key.
`static int`	`VK_F24` Constant for the F24 function key.
`static int`	`VK_F3` Constant for the F3 function key.
`static int`	`VK_F4` Constant for the F4 function key.
`static int`	`VK_F5` Constant for the F5 function key.
`static int`	`VK_F6` Constant for the F6 function key.
`static int`	`VK_F7` Constant for the F7 function key.
`static int`	`VK_F8` Constant for the F8 function key.
`static int`	`VK_F9` Constant for the F9 function key.
`static int`	`VK_FINAL`
`static int`	`VK_FIND`
`static int`	`VK_FULL_WIDTH` Constant for the Full-Width Characters function key.
`static int`	`VK_G`
`static int`	`VK_GREATER`
`static int`	`VK_H`
`static int`	`VK_HALF_WIDTH` Constant for the Half-Width Characters function key.
`static int`	`VK_HELP`
`static int`	`VK_HIRAGANA` Constant for the Hiragana function key.
`static int`	`VK_HOME`
`static int`	`VK_I`
`static int`	`VK_INPUT_METHOD_ON_OFF` Constant for the input method on/off key.
`static int`	`VK_INSERT`
`static int`	`VK_INVERTED_EXCLAMATION_MARK` Constant for the inverted exclamation mark key.
`static int`	`VK_J`
`static int`	`VK_JAPANESE_HIRAGANA` Constant for the Japanese-Hiragana function key.
`static int`	`VK_JAPANESE_KATAKANA` Constant for the Japanese-Katakana function key.
`static int`	`VK_JAPANESE_ROMAN` Constant for the Japanese-Roman function key.
`static int`	`VK_K`
`static int`	`VK_KANA`
`static int`	`VK_KANA_LOCK`

java.awt.event Class KeyEvent

java.awt.event
Class KeyEvent