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Chapter 20 The java.awt.event Package |
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Chapter 20 The java.awt.event Package |
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An event of this type indicates that the user has pressed or released a key or typed a character.
Call getID() to determine the particular type of key event that has occurred. The constant KEY_PRESSED indicates that a key has been pressed, while the constant KEY_RELEASED indicates that a key has been released. Not all keystrokes actually correspond to or generate Unicode characters. Modifier keys and function keys, for example, do not correspond to characters. Furthermore, for internationalized input, multiple keystrokes are sometimes required to generate a single character of input. Therefore, getID() returns a third constant, KEY_TYPED, to indicate a KeyEvent that actually contains a character value.
For KEY_PRESSED and KEY_RELEASED key events, use getKeyCode() to obtain the "virtual key code" of the key that was pressed or released. KeyEvent defines a number of VK_ constants that represent these "virtual keys." Note that not all keys on all keyboards have corresponding constants in the KeyEvent class, and not all keyboards can generate all of the virtual key codes defined by the class. In JDK 1.1, the VK_ constants for letter keys, number keys, and some other keys have the same values as the ASCII encodings of the letters and numbers. You should not rely on this to always be the case, however. If the key that was pressed or released corresponds directly to a Unicode character, you can obtain that character by calling getKeyChar(). If there is not a corresponding Unicode character, this method returns the constant CHAR_UNDEFINED. The isActionKey() method returns true if the key that was pressed or released does not have a corresponding character.
For KEY_TYPED key events, use getKeyChar() to return the Unicode character that was typed. If you call getKeyCode() for this type of key event, it returns VK_UNDEFINED.
See InputEvent for information on inherited methods you can use to obtain the keyboard modifiers that were down during the event and other important methods.
Use getComponent(), inherited from ComponentEvent, to determine what component the event occurred over.
The static method getKeyText() returns a (possibly localized) textual name for a given key code. The static method getKeyModifiersText() returns a (possibly localized) textual description for a set of modifiers.
The KeyEvent has methods that allow you to change the key code, key character, or modifiers of an event. These methods, along with the consume() method, allow a KeyListener to perform filtering of key events before they are passed to the underlying AWT component.
public class KeyEvent extends InputEvent {
// Public Constructors
public KeyEvent(Component source, int id, long when, int modifiers, int keyCode, char keyChar);
public KeyEvent(Component source, int id, long when, int modifiers, int keyCode);
// Constants
// Event Type Constants
public static final int KEY_FIRST;
public static final int KEY_LAST;
public static final int KEY_PRESSED;
public static final int KEY_RELEASED;
public static final int KEY_TYPED;
// Undefined Key and Character
public static final int VK_UNDEFINED;
public static final char CHAR_UNDEFINED;
// Alphanumeric Keys
public static final int VK_A, VK_B, VK_C, VK_D, VK_E, VK_F, VK_G, VK_H, VK_I;
public static final int VK_J, VK_K, VK_L, VK_M, VK_N, VK_O, VK_P, VK_Q, VK_R;
public static final int VK_S, VK_T, VK_U, VK_V, VK_W, VK_X, VK_Y, VK_Z;
public static final int VK_SPACE;
public static final int VK_0, VK_1, VK_2, VK_3, VK_4, VK_5, VK_6, VK_7, VK_8, VK_9;
public static final int VK_NUMPAD0, VK_NUMPAD1, VK_NUMPAD2, VK_NUMPAD3, VK_NUMPAD4;
public static final int VK_NUMPAD5, VK_NUMPAD6, VK_NUMPAD7, VK_NUMPAD8, VK_NUMPAD9;
// Control Keys
public static final int VK_BACK_SPACE, VK_ENTER, VK_ESCAPE, VK_TAB;
// Modifier Keys
public static final int VK_ALT, VK_CAPS_LOCK, VK_CONTROL, VK_META, VK_SHIFT;
// Function Keys
public static final int VK_F1, VK_F2, VK_F3, VK_F4, VK_F5, VK_F6;
public static final int VK_F7, VK_F8, VK_F9, VK_F10, VK_F11, VK_F12;
public static final int VK_PRINTSCREEN, VK_SCROLL_LOCK, VK_PAUSE;
public static final int VK_DELETE, VK_INSERT;
public static final int VK_PAGE_DOWN, VK_PAGE_UP;
public static final int VK_DOWN, VK_LEFT, VK_RIGHT, VK_UP;
public static final int VK_END, VK_HOME;
public static final int VK_ACCEPT, VK_NUM_LOCK, VK_CANCEL;
public static final int VK_CLEAR, VK_CONVERT, VK_FINAL;
public static final int VK_HELP, VK_KANA, VK_KANJI;
public static final int VK_MODECHANGE, VK_NONCONVERT;
// Punctuation Keys
public static final int VK_ADD, VK_BACK_QUOTE, VK_BACK_SLASH;
public static final int VK_CLOSE_BRACKET, VK_COMMA, VK_DECIMAL;
public static final int VK_DIVIDE, VK_EQUALS, VK_MULTIPLY;
public static final int VK_OPEN_BRACKET, VK_PERIOD, VK_QUOTE;
public static final int VK_SEMICOLON, VK_SEPARATER, VK_SLASH;
public static final int VK_SUBTRACT;
// Class Methods
public static String getKeyModifiersText(int modifiers);
public static String getKeyText(int keyCode);
// Public Instance Methods
public char getKeyChar();
public int getKeyCode();
public boolean isActionKey();
public String paramString(); // Overrides ComponentEvent
public void setKeyChar(char keyChar);
public void setKeyCode(int keyCode);
public void setModifiers(int modifiers);
}
Object->EventObject(Serializable)->AWTEvent->ComponentEvent->InputEvent->KeyEvent
AWTEventMulticaster.keyPressed(), AWTEventMulticaster.keyReleased(), AWTEventMulticaster.keyTyped(), Component.processKeyEvent(), KeyAdapter.keyPressed(), KeyAdapter.keyReleased(), KeyAdapter.keyTyped(), KeyListener.keyPressed(), KeyListener.keyReleased(), KeyListener.keyTyped()
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| java.awt.event.KeyAdapter (JDK 1.1) |  |
java.awt.event.KeyListener (JDK 1.1) |
