Module java.desktop
Package java.awt

# Interface KeyEventPostProcessor

All Known Implementing Classes:
  `DefaultFocusManager`, `DefaultKeyboardFocusManager`, `FocusManager`, `KeyboardFocusManager`

Functional Interface:
  This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface public interface KeyEventPostProcessor
A KeyEventPostProcessor cooperates with the current KeyboardFocusManager in the final resolution of all unconsumed KeyEvents. KeyEventPostProcessors registered with the current KeyboardFocusManager will receive KeyEvents after the KeyEvents have been dispatched to and handled by their targets. KeyEvents that would have been otherwise discarded because no Component in the application currently owns the focus will also be forwarded to registered KeyEventPostProcessors. This will allow applications to implement features that require global KeyEvent post-handling, such as menu shortcuts.

Note that the KeyboardFocusManager itself implements KeyEventPostProcessor. By default, the current KeyboardFocusManager will be the final KeyEventPostProcessor in the chain. The current KeyboardFocusManager cannot be completely deregistered as a KeyEventPostProcessor. However, if a KeyEventPostProcessor reports that no further post-processing of the KeyEvent should take place, the AWT will consider the event fully handled and will take no additional action with regard to the event. (While it is possible for client code to register the current KeyboardFocusManager as a KeyEventPostProcessor one or more times, this is usually unnecessary and not recommended.)

Since:
  1.4
See Also:
  - `KeyboardFocusManager.addKeyEventPostProcessor(java.awt.KeyEventPostProcessor)`
  - `KeyboardFocusManager.removeKeyEventPostProcessor(java.awt.KeyEventPostProcessor)`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `postProcessKeyEvent(KeyEvent e)`
  This method is called by the current KeyboardFocusManager, requesting that this KeyEventPostProcessor perform any necessary post-processing which should be part of the KeyEvent's final resolution.

- ## Method Details

  - ### postProcessKeyEvent

    boolean postProcessKeyEvent(KeyEvent e)
    This method is called by the current KeyboardFocusManager, requesting that this KeyEventPostProcessor perform any necessary post-processing which should be part of the KeyEvent's final resolution. At the time this method is invoked, typically the KeyEvent has already been dispatched to and handled by its target. However, if no Component in the application currently owns the focus, then the KeyEvent has not been dispatched to any Component. Typically, KeyEvent post-processing will be used to implement features which require global KeyEvent post-handling, such as menu shortcuts. Note that if a KeyEventPostProcessor wishes to dispatch the KeyEvent, it must use `redispatchEvent` to prevent the AWT from recursively requesting that this KeyEventPostProcessor perform post-processing of the event again.

    If an implementation of this method returns `false`, then the KeyEvent is passed to the next KeyEventPostProcessor in the chain, ending with the current KeyboardFocusManager. If an implementation returns `true`, the KeyEvent is assumed to have been fully handled (although this need not be the case), and the AWT will take no further action with regard to the KeyEvent. If an implementation consumes the KeyEvent but returns `false`, the consumed event will still be passed to the next KeyEventPostProcessor in the chain. It is important for developers to check whether the KeyEvent has been consumed before performing any post-processing of the KeyEvent. By default, the current KeyboardFocusManager will perform no post- processing in response to a consumed KeyEvent.

    Parameters:
      `e` - the KeyEvent to post-process
    Returns:
      `true` if the AWT should take no further action with regard to the KeyEvent; `false` otherwise
    See Also:
      - `KeyboardFocusManager.redispatchEvent(java.awt.Component, java.awt.AWTEvent)`