Class KeyStroke

All Implemented Interfaces:
Serializable
public class KeyStroke
extends AWTKeyStroke

A KeyStroke represents a key action on the keyboard, or equivalent input device. KeyStrokes can correspond to only a press or release of a particular key, just as KEY_PRESSED and KEY_RELEASED KeyEvents do; alternately, they can correspond to typing a specific Java character, just as KEY_TYPED KeyEvents do. In all cases, KeyStrokes can specify modifiers (alt, shift, control, meta, altGraph, or a combination thereof) which must be present during the action for an exact match.

KeyStrokes are used to define high-level (semantic) action events. Instead of trapping every keystroke and throwing away the ones you are not interested in, those keystrokes you care about automatically initiate actions on the Components with which they are registered.

KeyStrokes are immutable, and are intended to be unique. Client code cannot create a KeyStroke; a variant of getKeyStroke must be used instead. These factory methods allow the KeyStroke implementation to cache and share instances efficiently.

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 JavaBeans™ has been added to the java.beans package. Please see XMLEncoder.

Since:
1.2
See Also:
Keymap, getKeyStroke(char), Serialized Form

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type Method Description
static KeyStroke getKeyStroke​(char keyChar)

Returns a shared instance of a KeyStroke that represents a KEY_TYPED event for the specified character.
static KeyStroke getKeyStroke​(char keyChar, boolean onKeyRelease)

Deprecated.

use getKeyStroke(char)
static KeyStroke getKeyStroke​(int keyCode, int modifiers)

Returns a shared instance of a KeyStroke, given a numeric key code and a set of modifiers.
static KeyStroke getKeyStroke​(int keyCode, int modifiers, boolean onKeyRelease)

Returns a shared instance of a KeyStroke, given a numeric key code and a set of modifiers, specifying whether the key is activated when it is pressed or released.
static KeyStroke getKeyStroke​(Character keyChar, int modifiers)

Returns a shared instance of a KeyStroke that represents a KEY_TYPED event for the specified Character object and a set of modifiers.
static KeyStroke getKeyStroke​(String s)

Parses a string and returns a KeyStroke.
static KeyStroke getKeyStrokeForEvent​(KeyEvent anEvent)

Returns a KeyStroke which represents the stroke which generated a given KeyEvent.

Methods declared in class java.awt.AWTKeyStroke

equals, getAWTKeyStroke, getAWTKeyStroke, getAWTKeyStroke, getAWTKeyStroke, getAWTKeyStroke, getAWTKeyStrokeForEvent, getKeyChar, getKeyCode, getKeyEventType, getModifiers, hashCode, isOnKeyRelease, readResolve, registerSubclass, toString

Methods declared in class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

getKeyStroke

public static KeyStroke getKeyStroke​(char keyChar)

Returns a shared instance of a KeyStroke that represents a KEY_TYPED event for the specified character.

Parameters:
keyChar - the character value for a keyboard key
Returns:
a KeyStroke object for that key

getKeyStroke

@Deprecated
public static KeyStroke getKeyStroke​(char keyChar,
                                     boolean onKeyRelease)
Deprecated.
use getKeyStroke(char)

Returns an instance of a KeyStroke, specifying whether the key is considered to be activated when it is pressed or released. Unlike all other factory methods in this class, the instances returned by this method are not necessarily cached or shared.

Parameters:
keyChar - the character value for a keyboard key
onKeyRelease - true if this KeyStroke corresponds to a key release; false otherwise.
Returns:
a KeyStroke object for that key

getKeyStroke

public static KeyStroke getKeyStroke​(Character keyChar,
                                     int modifiers)

Returns a shared instance of a KeyStroke that represents a KEY_TYPED event for the specified Character object and a set of modifiers. Note that the first parameter is of type Character rather than char. This is to avoid inadvertent clashes with calls to getKeyStroke(int keyCode, int modifiers). The modifiers consist of any combination of following:

  • java.awt.event.InputEvent.SHIFT_DOWN_MASK
  • java.awt.event.InputEvent.CTRL_DOWN_MASK
  • java.awt.event.InputEvent.META_DOWN_MASK
  • java.awt.event.InputEvent.ALT_DOWN_MASK
  • java.awt.event.InputEvent.ALT_GRAPH_DOWN_MASK
The old modifiers listed below also can be used, but they are mapped to _DOWN_ modifiers.
  • java.awt.event.InputEvent.SHIFT_MASK
  • java.awt.event.InputEvent.CTRL_MASK
  • java.awt.event.InputEvent.META_MASK
  • java.awt.event.InputEvent.ALT_MASK
  • java.awt.event.InputEvent.ALT_GRAPH_MASK
also can be used, but they are mapped to _DOWN_ modifiers. Since these numbers are all different powers of two, any combination of them is an integer in which each bit represents a different modifier key. Use 0 to specify no modifiers.
Parameters:
keyChar - the Character object for a keyboard character
modifiers - a bitwise-ored combination of any modifiers
Returns:
an KeyStroke object for that key
Throws:
IllegalArgumentException - if keyChar is null
Since:
1.3
See Also:
InputEvent

getKeyStroke

public static KeyStroke getKeyStroke​(int keyCode,
                                     int modifiers,
                                     boolean onKeyRelease)

Returns a shared instance of a KeyStroke, given a numeric key code and a set of modifiers, specifying whether the key is activated when it is pressed or released.

The "virtual key" constants defined in java.awt.event.KeyEvent can be used to specify the key code. For example:

  • java.awt.event.KeyEvent.VK_ENTER
  • java.awt.event.KeyEvent.VK_TAB
  • java.awt.event.KeyEvent.VK_SPACE
Alternatively, the key code may be obtained by calling java.awt.event.KeyEvent.getExtendedKeyCodeForChar. The modifiers consist of any combination of:
  • java.awt.event.InputEvent.SHIFT_DOWN_MASK
  • java.awt.event.InputEvent.CTRL_DOWN_MASK
  • java.awt.event.InputEvent.META_DOWN_MASK
  • java.awt.event.InputEvent.ALT_DOWN_MASK
  • java.awt.event.InputEvent.ALT_GRAPH_DOWN_MASK
The old modifiers
  • java.awt.event.InputEvent.SHIFT_MASK
  • java.awt.event.InputEvent.CTRL_MASK
  • java.awt.event.InputEvent.META_MASK
  • java.awt.event.InputEvent.ALT_MASK
  • java.awt.event.InputEvent.ALT_GRAPH_MASK
also can be used, but they are mapped to _DOWN_ modifiers. Since these numbers are all different powers of two, any combination of them is an integer in which each bit represents a different modifier key. Use 0 to specify no modifiers.
Parameters:
keyCode - an int specifying the numeric code for a keyboard key
modifiers - a bitwise-ored combination of any modifiers
onKeyRelease - true if the KeyStroke should represent a key release; false otherwise.
Returns:
a KeyStroke object for that key
See Also:
KeyEvent, InputEvent

getKeyStroke

public static KeyStroke getKeyStroke​(int keyCode,
                                     int modifiers)

Returns a shared instance of a KeyStroke, given a numeric key code and a set of modifiers. The returned KeyStroke will correspond to a key press.

The "virtual key" constants defined in java.awt.event.KeyEvent can be used to specify the key code. For example:

  • java.awt.event.KeyEvent.VK_ENTER
  • java.awt.event.KeyEvent.VK_TAB
  • java.awt.event.KeyEvent.VK_SPACE
Alternatively, the key code may be obtained by calling java.awt.event.KeyEvent.getExtendedKeyCodeForChar. The modifiers consist of any combination of:
  • java.awt.event.InputEvent.SHIFT_DOWN_MASK
  • java.awt.event.InputEvent.CTRL_DOWN_MASK
  • java.awt.event.InputEvent.META_DOWN_MASK
  • java.awt.event.InputEvent.ALT_DOWN_MASK
  • java.awt.event.InputEvent.ALT_GRAPH_DOWN_MASK
The old modifiers
  • java.awt.event.InputEvent.SHIFT_MASK
  • java.awt.event.InputEvent.CTRL_MASK
  • java.awt.event.InputEvent.META_MASK
  • java.awt.event.InputEvent.ALT_MASK
  • java.awt.event.InputEvent.ALT_GRAPH_MASK
also can be used, but they are mapped to _DOWN_ modifiers. Since these numbers are all different powers of two, any combination of them is an integer in which each bit represents a different modifier key. Use 0 to specify no modifiers.
Parameters:
keyCode - an int specifying the numeric code for a keyboard key
modifiers - a bitwise-ored combination of any modifiers
Returns:
a KeyStroke object for that key
See Also:
KeyEvent, InputEvent

getKeyStrokeForEvent

public static KeyStroke getKeyStrokeForEvent​(KeyEvent anEvent)

Returns a KeyStroke which represents the stroke which generated a given KeyEvent.

This method obtains the keyChar from a KeyTyped event, and the keyCode from a KeyPressed or KeyReleased event. The KeyEvent modifiers are obtained for all three types of KeyEvent.

Parameters:
anEvent - the KeyEvent from which to obtain the KeyStroke
Returns:
the KeyStroke that precipitated the event
Throws:
NullPointerException - if anEvent is null

getKeyStroke

public static KeyStroke getKeyStroke​(String s)

Parses a string and returns a KeyStroke. The string must have the following syntax: 

<modifiers>* (<typedID> | <pressedReleasedID>)

    modifiers := shift | control | ctrl | meta | alt | altGraph
    typedID := typed <typedKey>
    typedKey := string of length 1 giving Unicode character.
    pressedReleasedID := (pressed | released) key
    key := KeyEvent key code name, i.e. the name following "VK_".
If typed, pressed or released is not specified, pressed is assumed. Here are some examples: 
"INSERT" => getKeyStroke(KeyEvent.VK_INSERT, 0);
     "control DELETE" => getKeyStroke(KeyEvent.VK_DELETE, InputEvent.CTRL_MASK);
     "alt shift X" => getKeyStroke(KeyEvent.VK_X, InputEvent.ALT_MASK | InputEvent.SHIFT_MASK);
     "alt shift released X" => getKeyStroke(KeyEvent.VK_X, InputEvent.ALT_MASK | InputEvent.SHIFT_MASK, true);
     "typed a" => getKeyStroke('a');
In order to maintain backward-compatibility, specifying a null String, or a String which is formatted incorrectly, returns null.
Parameters:
s - a String formatted as described above
Returns:
a KeyStroke object for that String, or null if the specified String is null, or is formatted incorrectly
See Also:
KeyEvent