An event which indicates that the mouse wheel was rotated in a component.
A wheel mouse is a mouse which has a wheel in place of the middle button.
This wheel can be rotated towards or away from the user. Mouse wheels are
most often used for scrolling, though other uses are possible.
A MouseWheelEvent object is passed to every MouseWheelListener
object which registered to receive the "interesting" mouse events using the
component's addMouseWheelListener method. Each such listener
object gets a MouseEvent containing the mouse event.
Due to the mouse wheel's special relationship to scrolling Components,
MouseWheelEvents are delivered somewhat differently than other MouseEvents.
This is because while other MouseEvents usually affect a change on
the Component directly under the mouse
cursor (for instance, when clicking a button), MouseWheelEvents often have
an effect away from the mouse cursor (moving the wheel while
over a Component inside a ScrollPane should scroll one of the
Scrollbars on the ScrollPane).
MouseWheelEvents start delivery from the Component underneath the
mouse cursor. If MouseWheelEvents are not enabled on the
Component, the event is delivered to the first ancestor
Container with MouseWheelEvents enabled. This will usually be
a ScrollPane with wheel scrolling enabled. The source
Component and x,y coordinates will be relative to the event's
final destination (the ScrollPane). This allows a complex
GUI to be installed without modification into a ScrollPane, and
for all MouseWheelEvents to be delivered to the ScrollPane for
scrolling.
Some AWT Components are implemented using native widgets which
display their own scrollbars and handle their own scrolling.
The particular Components for which this is true will vary from
platform to platform. When the mouse wheel is
moved over one of these Components, the event is delivered straight to
the native widget, and not propagated to ancestors.
Platforms offer customization of the amount of scrolling that
should take place when the mouse wheel is moved. The two most
common settings are to scroll a certain number of "units"
(commonly lines of text in a text-based component) or an entire "block"
(similar to page-up/page-down). The MouseWheelEvent offers
methods for conforming to the underlying platform settings. These
platform settings can be changed at any time by the user. MouseWheelEvents
reflect the most recent settings.
A wheel mouse is a mouse which has a wheel in place of the middle button. This wheel can be rotated towards or away from the user. Mouse wheels are most often used for scrolling, though other uses are possible.
A MouseWheelEvent object is passed to every
MouseWheelListenerobject which registered to receive the "interesting" mouse events using the component'saddMouseWheelListenermethod. Each such listener object gets aMouseEventcontaining the mouse event.Due to the mouse wheel's special relationship to scrolling Components, MouseWheelEvents are delivered somewhat differently than other MouseEvents. This is because while other MouseEvents usually affect a change on the Component directly under the mouse cursor (for instance, when clicking a button), MouseWheelEvents often have an effect away from the mouse cursor (moving the wheel while over a Component inside a ScrollPane should scroll one of the Scrollbars on the ScrollPane).
MouseWheelEvents start delivery from the Component underneath the mouse cursor. If MouseWheelEvents are not enabled on the Component, the event is delivered to the first ancestor Container with MouseWheelEvents enabled. This will usually be a ScrollPane with wheel scrolling enabled. The source Component and x,y coordinates will be relative to the event's final destination (the ScrollPane). This allows a complex GUI to be installed without modification into a ScrollPane, and for all MouseWheelEvents to be delivered to the ScrollPane for scrolling.
Some AWT Components are implemented using native widgets which display their own scrollbars and handle their own scrolling. The particular Components for which this is true will vary from platform to platform. When the mouse wheel is moved over one of these Components, the event is delivered straight to the native widget, and not propagated to ancestors.
Platforms offer customization of the amount of scrolling that should take place when the mouse wheel is moved. The two most common settings are to scroll a certain number of "units" (commonly lines of text in a text-based component) or an entire "block" (similar to page-up/page-down). The MouseWheelEvent offers methods for conforming to the underlying platform settings. These platform settings can be changed at any time by the user. MouseWheelEvents reflect the most recent settings.