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.
The MouseWheelEvent class includes methods for
getting the number of "clicks" by which the mouse wheel is rotated.
The getWheelRotation method returns the integer number
of "clicks" corresponding to the number of notches by which the wheel was
rotated. In addition to this method, the MouseWheelEvent
class provides the getPreciseWheelRotation method which returns
a double number of "clicks" in case a partial rotation occurred.
The getPreciseWheelRotation method is useful if a mouse supports
a high-resolution wheel, such as a freely rotating wheel with no
notches. Applications can benefit by using this method to process
mouse wheel events more precisely, and thus, making visual perception
smoother.
MouseWheelListener, java.awt.ScrollPane , java.awt.ScrollPane#setWheelScrollingEnabled(boolean) , javax.swing.JScrollPane , javax.swing.JScrollPane#setWheelScrollingEnabled(boolean)
| Modifier and Type | Field and Description |
|---|---|
| pack-priv double | |
| pack-priv int | |
| pack-priv int | |
| private static final long | serialVersionUID
Use serialVersionUID from JDK 1.6 for interoperability.
|
| public static final int | WHEEL_BLOCK_SCROLL
Constant representing scrolling by a "block" (like scrolling with page-up, page-down keys) |
| public static final int | WHEEL_UNIT_SCROLL
Constant representing scrolling by "units" (like scrolling with the arrow keys) |
| pack-priv int |
| Access | Constructor and Description |
|---|---|
| public | MouseWheelEvent(Component
the source, int Component that originated
the eventthe integer that identifies the event id, long a long that gives the time the event occurred when, int the modifier keys down during event
(shift, ctrl, alt, meta) modifiers, int the horizontal x coordinate for the mouse location x, int the vertical y coordinate for the mouse location y, int the number of mouse clicks associated with event clickCount, boolean a boolean, true if this event is a trigger for a
popup-menu popupTrigger, int the type of scrolling which should take place in
response to this event; valid values are
scrollType, int WHEEL_UNIT_SCROLL and
WHEEL_BLOCK_SCROLLfor scrollType scrollAmount, int WHEEL_UNIT_SCROLL,
the number of units to be scrolledthe integer number of "clicks" by which the mouse
wheel was rotated wheelRotation)Constructs a |
| public | MouseWheelEvent(Component
the source, int Component that originated
the eventthe integer that identifies the event id, long a long that gives the time the event occurred when, int the modifier keys down during event
(shift, ctrl, alt, meta) modifiers, int the horizontal x coordinate for the mouse location x, int the vertical y coordinate for the mouse location y, int the absolute horizontal x coordinate for the mouse location xAbs, int the absolute vertical y coordinate for the mouse location yAbs, int the number of mouse clicks associated with event clickCount, boolean a boolean, true if this event is a trigger for a
popup-menu popupTrigger, int the type of scrolling which should take place in
response to this event; valid values are
scrollType, int WHEEL_UNIT_SCROLL and
WHEEL_BLOCK_SCROLLfor scrollType scrollAmount, int WHEEL_UNIT_SCROLL,
the number of units to be scrolledthe integer number of "clicks" by which the mouse
wheel was rotated wheelRotation)Constructs a |
| public | MouseWheelEvent(Component
the source, int Component that originated the eventthe integer value that identifies the event id, long a long value that gives the time when the event occurred when, int the modifier keys down during event
(shift, ctrl, alt, meta) modifiers, int the horizontal x, int x coordinate for the
mouse locationthe vertical y, int y coordinate for the
mouse locationthe absolute horizontal xAbs, int x coordinate for
the mouse locationthe absolute vertical yAbs, int y coordinate for
the mouse locationthe number of mouse clicks associated with the event clickCount, boolean a boolean value, popupTrigger, int true if this event is a trigger
for a popup-menuthe type of scrolling which should take place in
response to this event; valid values are
scrollType, int WHEEL_UNIT_SCROLL and
WHEEL_BLOCK_SCROLLfor scrollType scrollAmount, int WHEEL_UNIT_SCROLL,
the number of units to be scrolledthe integer number of "clicks" by which the mouse wheel
was rotated wheelRotation, double the double number of "clicks" by which the mouse wheel
was rotated preciseWheelRotation)Constructs a |
| Modifier and Type | Method and Description |
|---|---|
| public double | Returns: negative values if the mouse wheel was rotated up or away from the user, and positive values if the mouse wheel was rotated down or towards the userReturns the number of "clicks" the mouse wheel was rotated, as a double. |
| public int | Returns: number of units to scroll, or an undefined value ifgetScrollType returns
MouseWheelEvent.WHEEL_BLOCK_SCROLLReturns the number of units that should be scrolled per click of mouse wheel rotation. |
| public int | Returns: either MouseWheelEvent.WHEEL_UNIT_SCROLL or MouseWheelEvent.WHEEL_BLOCK_SCROLL, depending on the configuration of the native platform.Returns the type of scrolling that should take place in response to this event. |
| public int | Returns: the number of units to scroll based on the direction and amount of mouse wheel rotation, and on the wheel scrolling settings of the native platformThis is a convenience method to aid in the implementation of the common-case MouseWheelListener - to scroll a ScrollPane or JScrollPane by an amount which conforms to the platform settings. |
| public int | Returns: negative values if the mouse wheel was rotated up/away from the user, and positive values if the mouse wheel was rotated down/ towards the userReturns the number of "clicks" the mouse wheel was rotated, as an integer. |
| public String | Returns: a string identifying the event and its attributesOverrides java. Returns a parameter string identifying this event. |
| preciseWheelRotation | back to summary |
|---|---|
pack-priv double preciseWheelRotation
| |
| scrollAmount | back to summary |
|---|---|
pack-priv int scrollAmount
| |
| scrollType | back to summary |
|---|---|
pack-priv int scrollType
| |
| serialVersionUID | back to summary |
|---|---|
| private static final long serialVersionUID Hides java. Use serialVersionUID from JDK 1.6 for interoperability. | |
| WHEEL_BLOCK_SCROLL | back to summary |
|---|---|
| public static final int WHEEL_BLOCK_SCROLL Constant representing scrolling by a "block" (like scrolling with page-up, page-down keys)
| |
| WHEEL_UNIT_SCROLL | back to summary |
|---|---|
| public static final int WHEEL_UNIT_SCROLL Constant representing scrolling by "units" (like scrolling with the arrow keys)
| |
| wheelRotation | back to summary |
|---|---|
pack-priv int wheelRotation
| |
| MouseWheelEvent | back to summary |
|---|---|
| public MouseWheelEvent(Component source, int id, long when, int modifiers, int x, int y, int clickCount, boolean popupTrigger, int scrollType, int scrollAmount, int wheelRotation) Constructs a Absolute coordinates xAbs and yAbs are set to source's location on screen plus relative coordinates x and y. xAbs and yAbs are set to zero if the source is not showing. Note that passing in an invalid
| |
| MouseWheelEvent | back to summary |
|---|---|
| public MouseWheelEvent(Component source, int id, long when, int modifiers, int x, int y, int xAbs, int yAbs, int clickCount, boolean popupTrigger, int scrollType, int scrollAmount, int wheelRotation) Constructs a Note that passing in an invalid Even if inconsistent values for relative and absolute coordinates are passed to the constructor, the MouseWheelEvent instance is still created and no exception is thrown.
| |
| MouseWheelEvent | back to summary |
|---|---|
| public MouseWheelEvent(Component source, int id, long when, int modifiers, int x, int y, int xAbs, int yAbs, int clickCount, boolean popupTrigger, int scrollType, int scrollAmount, int wheelRotation, double preciseWheelRotation) Constructs a Note that passing in an invalid Even if inconsistent values for relative and absolute coordinates
are passed to the constructor, a
| |
| getPreciseWheelRotation | back to summary |
|---|---|
| public double getPreciseWheelRotation() Returns the number of "clicks" the mouse wheel was rotated, as a double. A partial rotation may occur if the mouse supports a high-resolution wheel. In this case, the return value will include a fractional "click".
| |
| getScrollAmount | back to summary |
|---|---|
| public int getScrollAmount() Returns the number of units that should be scrolled per
click of mouse wheel rotation.
Only valid if
| |
| getScrollType | back to summary |
|---|---|
| public int getScrollType() Returns the type of scrolling that should take place in response to this event. This is determined by the native platform. Legal values are:
| |
| getUnitsToScroll | back to summary |
|---|---|
| public int getUnitsToScroll() This is a convenience method to aid in the implementation of
the common-case MouseWheelListener - to scroll a ScrollPane or
JScrollPane by an amount which conforms to the platform settings.
(Note, however, that
This method returns the number of units to scroll when scroll type is
MouseWheelEvent.WHEEL_UNIT_SCROLL, and should only be called if
Direction of scroll, amount of wheel movement, and platform settings for wheel scrolling are all accounted for. This method does not and cannot take into account value of the Adjustable/Scrollable unit increment, as this will vary among scrolling components. A simplified example of how this method might be used in a listener:
mouseWheelMoved(MouseWheelEvent event) {
ScrollPane sp = getScrollPaneFromSomewhere();
Adjustable adj = sp.getVAdjustable()
if (MouseWheelEvent.getScrollType() == WHEEL_UNIT_SCROLL) {
int totalScrollAmount =
event.getUnitsToScroll() *
adj.getUnitIncrement();
adj.setValue(adj.getValue() + totalScrollAmount);
}
}
| |
| getWheelRotation | back to summary |
|---|---|
| public int getWheelRotation() Returns the number of "clicks" the mouse wheel was rotated, as an integer. A partial rotation may occur if the mouse supports a high-resolution wheel. In this case, the method returns zero until a full "click" has been accumulated.
| |
| paramString | back to summary |
|---|---|
| public String paramString() Overrides java. Returns a parameter string identifying this event. This method is useful for event-logging and for debugging.
| |