java.awt.event

Class MouseWheelEvent

public class MouseWheelEvent extends MouseEvent

This event is generated for a mouse wheel rotation. The wheel (the middle mouse button on most modern mice) can be rotated towards or away from the user, and is often used for scrolling.

Because of the special use for scrolling components, MouseWheelEvents often affect a different component than the one located at the point of the event. If the component under the mouse cursor does not accept wheel events, the event is passed to the first ancestor container which does. This is often a ScrollPane, which knows how to scroll. If an AWT component is built from a native widget that knows how to use mouse wheel events, that component will consume the event.

The two most common scroll types are "units" (lines at a time) or "blocks" (pages at a time). The initial setting is taken from the platform, although the user can adjust the setting at any time.

Since: 1.4

UNKNOWN: updated to 1.4

Field Summary
static int	WHEEL_BLOCK_SCROLL Indicates scrolling by blocks (pages).
static int	WHEEL_UNIT_SCROLL Indicates scrolling by units (lines).

Constructor Summary
	MouseWheelEvent(Component source, int id, long when, int modifiers, int x, int y, int clickCount, boolean popupTrigger, int scrollType, int scrollAmount, int wheelRotation) Initializes a new instance of `MouseWheelEvent` with the specified information.

Method Summary
int	getScrollAmount() Returns the number of units to scroll in response to this event.
int	getScrollType() This method returns the scrolling pattern this event requests.
int	getUnitsToScroll() This is a convenience method which aids in a common listener for scrolling a scrollpane (although this is already built into ScrollPane and JScrollPane).
int	getWheelRotation() Gets the number of "clicks" the wheel was rotated.
String	paramString() Returns a string identifying this event.

Field Detail

WHEEL_BLOCK_SCROLL

public static final int WHEEL_BLOCK_SCROLL

Indicates scrolling by blocks (pages).

WHEEL_UNIT_SCROLL

public static final int WHEEL_UNIT_SCROLL

Indicates scrolling by units (lines).

Constructor Detail

MouseWheelEvent

public MouseWheelEvent(Component source, int id, long when, int modifiers, int x, int y, int clickCount, boolean popupTrigger, int scrollType, int scrollAmount, int wheelRotation)

Initializes a new instance of MouseWheelEvent with the specified information. Note that an invalid id leads to unspecified results.

Parameters: source the source of the event id the event id when the timestamp of when the event occurred modifiers any modifier bits for this event x the X coordinate of the mouse point y the Y coordinate of the mouse point clickCount the number of mouse clicks for this event popupTrigger true if this event triggers a popup menu scrollType one of {@link #WHEEL_UNIT_SCROLL}, {@link #WHEEL_BLOCK_SCROLL} scrollAmount the number of units to scroll, ignored for block type wheelRotation the number of rotation "clicks"

Throws: IllegalArgumentException if source is null

Method Detail

getScrollAmount

public int getScrollAmount()

Returns the number of units to scroll in response to this event. This only makes sense when the scroll type is WHEEL_UNIT_SCROLL.

Returns: the number of scroll units, if defined

getScrollType

public int getScrollType()

This method returns the scrolling pattern this event requests. Legal values are {@link #WHEEL_UNIT_SCROLL} and {@link #WHEEL_BLOCK_SCROLL}.

Returns: the scroll type

getUnitsToScroll

public int getUnitsToScroll()

This is a convenience method which aids in a common listener for scrolling a scrollpane (although this is already built into ScrollPane and JScrollPane). This method only makes sense when getScrollType() returns WHEEL_UNIT_SCROLL.

This accounts for direction of scroll and amount of wheel movement, as interpreted by the platform settings.

Returns: the number of units to scroll

getWheelRotation

public int getWheelRotation()

Gets the number of "clicks" the wheel was rotated. Negative values move up (away) from the user, positive values move down (towards) the user.

Returns: the number of rotation clicks

paramString

public String paramString()

Returns a string identifying this event. For mouse wheel events, this is

super.paramString() + ",scrollType=WHEEL_" +
 (getScrollType() == WHEEL_UNIT_SCROLL ? "UNIT" : "BLOCK")
 + "_SCROLL,scrollAmount=" + getScrollAmount() + ",wheelRotation="
 + getWheelRotation()

Returns: a string identifying this event