WindowFocusListener (Java SE 26 & JDK 26)
Description: declaration: module: java.desktop, package: java.awt.event, interface: WindowFocusListener
Keywords: java.awt.event.WindowFocusListener interface

# Interface WindowFocusListener

All Superinterfaces:
  `EventListener`

All Known Implementing Classes:
  `AWTEventMulticaster, BasicToolBarUI.FrameListener, JMenu.WinListener, WindowAdapter`

public interface WindowFocusListener extends EventListener
The listener interface for receiving `WindowEvents`, including `WINDOW_GAINED_FOCUS` and `WINDOW_LOST_FOCUS` events. The class that is interested in processing a `WindowEvent` either implements this interface (and all the methods it contains) or extends the abstract `WindowAdapter` class (overriding only the methods of interest). The listener object created from that class is then registered with a `Window` using the `Window`'s `addWindowFocusListener` method. When the `Window`'s status changes by virtue of it being opened, closed, activated, deactivated, iconified, or deiconified, or by focus being transferred into or out of the `Window`, the relevant method in the listener object is invoked, and the `WindowEvent` is passed to it.

Since:
  1.4
See Also:
  - `WindowAdapter`
  - `WindowEvent`
  - Tutorial: Writing a Window Listener

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `windowGainedFocus(WindowEvent e)`
  Invoked when the Window is set to be the focused Window, which means that the Window, or one of its subcomponents, will receive keyboard events.
  `void`
  `windowLostFocus(WindowEvent e)`
  Invoked when the Window is no longer the focused Window, which means that keyboard events will no longer be delivered to the Window or any of its subcomponents.

- ## Method Details

  - ### windowGainedFocus

    void windowGainedFocus(WindowEvent e)
    Invoked when the Window is set to be the focused Window, which means that the Window, or one of its subcomponents, will receive keyboard events.
    Parameters:
      `e` - the event to be processed

  - ### windowLostFocus

    void windowLostFocus(WindowEvent e)
    Invoked when the Window is no longer the focused Window, which means that keyboard events will no longer be delivered to the Window or any of its subcomponents.
    Parameters:
      `e` - the event to be processed