Listening for window events
To listen for the events dispatched by a window, register a listener with the window instance. For example, to listen for the closing event, register a listener with the window as follows:
myWindow.addEventListener(Event.CLOSING, onClosingEvent);
When an event is dispatched, the target property references the window sending
the event.
Most window events have two related messages. The first message signals that a window change is imminent (and can be canceled), while the second message signals that the change has occurred. For example, when a user clicks the close button of a window, the closing event message is dispatched. If no listeners cancel the event, the window closes and the close event is dispatched to any listeners.
Typically, the warning events, such as closing, are only dispatched when
system chrome has been used to trigger an event. Calling the window close()
method, for example, does not automatically dispatch the closing event—only
the close event is dispatched. You can, however, construct a closing event
object and dispatch it using the window dispatchEvent() method.
The window events that dispatch an Event object are:
| Event | Description |
|---|---|
| activate | Dispatched when the window receives focus. |
| deactivate | Dispatched when the window loses focus |
| closing | Dispatched when the window is about to close. This only occurs automatically when the system chrome close button is pressed or, on Mac OS X, when the Quit command is invoked. |
| close | Dispatched when the window has closed. |
The window events that dispatch an NativeWindowBoundsEvent object are:
| Event | Description |
|---|---|
| moving | Dispatched immediately before the top-left corner of the window changes position, either as a result of moving, resizing or changing the window display state. |
| move | Dispatched after the top-left corner has changed position. |
| resizing | Dispatched immediately before the window width or height changes either as a result of resizing or a display state change. |
| resize | Dispatched after the window has changed size. |
For NativeWindowBoundsEvent events, you can use the beforeBounds and
afterBounds properties to determine the window bounds before and after the
impending or completed change.
The window events that dispatch an NativeWindowDisplayStateEvent object are:
| Event | Description |
|---|---|
| displayStateChanging | Dispatched immediately before the window display state changes. |
| displayStateChange | Dispatched after the window display state has changed. |
For NativeWindowDisplayStateEvent events, you can use the beforeDisplayState
and afterDisplayState properties to determine the window display state before
and after the impending or completed change.
On some Linux window managers, a display state change event is not dispatched when a window with a maximum size setting is maximized. (The window is set to the maximized display state, but is not resized.)