* 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 {@link #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 {@link #getPreciseWheelRotation} method which returns
* a double number of "clicks" in case a partial rotation occurred.
* The {@link #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.
*
* @author Brent Christian
* @see MouseWheelListener
* @see java.awt.ScrollPane
* @see java.awt.ScrollPane#setWheelScrollingEnabled(boolean)
* @see javax.swing.JScrollPane
* @see javax.swing.JScrollPane#setWheelScrollingEnabled(boolean)
* @since 1.4
*/
public class MouseWheelEvent extends MouseEvent {
/**
* Constant representing scrolling by "units" (like scrolling with the
* arrow keys)
*
* @see #getScrollType
*/
@Native public static final int WHEEL_UNIT_SCROLL = 0;
/**
* Constant representing scrolling by a "block" (like scrolling
* with page-up, page-down keys)
*
* @see #getScrollType
*/
@Native public static final int WHEEL_BLOCK_SCROLL = 1;
/**
* Indicates what sort of scrolling should take place in response to this
* event, based on platform settings. Legal values are:
*
MouseWheelEvent object with the
* specified source component, type, modifiers, coordinates,
* scroll type, scroll amount, and wheel rotation.
* 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 id results in
* unspecified behavior. This method throws an
* IllegalArgumentException if source
* is null.
*
* @param source the Component that originated
* the event
* @param id the integer that identifies the event
* @param when a long that gives the time the event occurred
* @param modifiers the modifier keys down during event
* (shift, ctrl, alt, meta)
* @param x the horizontal x coordinate for the mouse location
* @param y the vertical y coordinate for the mouse location
* @param clickCount the number of mouse clicks associated with event
* @param popupTrigger a boolean, true if this event is a trigger for a
* popup-menu
* @param scrollType the type of scrolling which should take place in
* response to this event; valid values are
* WHEEL_UNIT_SCROLL and
* WHEEL_BLOCK_SCROLL
* @param scrollAmount for scrollType WHEEL_UNIT_SCROLL,
* the number of units to be scrolled
* @param wheelRotation the integer number of "clicks" by which the mouse
* wheel was rotated
*
* @throws IllegalArgumentException if source is null
* @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, boolean)
* @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, int, int, boolean, int)
*/
public MouseWheelEvent (Component source, int id, long when, int modifiers,
int x, int y, int clickCount, boolean popupTrigger,
int scrollType, int scrollAmount, int wheelRotation) {
this(source, id, when, modifiers, x, y, 0, 0, clickCount,
popupTrigger, scrollType, scrollAmount, wheelRotation);
}
/**
* Constructs a MouseWheelEvent object with the
* specified source component, type, modifiers, coordinates,
* absolute coordinates, scroll type, scroll amount, and wheel rotation.
*
Note that passing in an invalid id results in
* unspecified behavior. This method throws an
* IllegalArgumentException if source
* is null.
* 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.
*
* @param source the Component that originated
* the event
* @param id the integer that identifies the event
* @param when a long that gives the time the event occurred
* @param modifiers the modifier keys down during event
* (shift, ctrl, alt, meta)
* @param x the horizontal x coordinate for the mouse location
* @param y the vertical y coordinate for the mouse location
* @param xAbs the absolute horizontal x coordinate for the mouse location
* @param yAbs the absolute vertical y coordinate for the mouse location
* @param clickCount the number of mouse clicks associated with event
* @param popupTrigger a boolean, true if this event is a trigger for a
* popup-menu
* @param scrollType the type of scrolling which should take place in
* response to this event; valid values are
* WHEEL_UNIT_SCROLL and
* WHEEL_BLOCK_SCROLL
* @param scrollAmount for scrollType WHEEL_UNIT_SCROLL,
* the number of units to be scrolled
* @param wheelRotation the integer number of "clicks" by which the mouse
* wheel was rotated
*
* @throws IllegalArgumentException if source is null
* @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, boolean)
* @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, int, int, boolean, int)
* @since 1.6
*/
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) {
this(source, id, when, modifiers, x, y, xAbs, yAbs, clickCount, popupTrigger,
scrollType, scrollAmount, wheelRotation, wheelRotation);
}
/**
* Constructs a MouseWheelEvent object with the specified
* source component, type, modifiers, coordinates, absolute coordinates,
* scroll type, scroll amount, and wheel rotation.
*
Note that passing in an invalid id parameter results
* in unspecified behavior. This method throws an
* IllegalArgumentException if source equals
* null.
*
Even if inconsistent values for relative and absolute coordinates
* are passed to the constructor, a MouseWheelEvent instance
* is still created and no exception is thrown.
*
* @param source the Component that originated the event
* @param id the integer value that identifies the event
* @param when a long value that gives the time when the event occurred
* @param modifiers the modifier keys down during event
* (shift, ctrl, alt, meta)
* @param x the horizontal x coordinate for the
* mouse location
* @param y the vertical y coordinate for the
* mouse location
* @param xAbs the absolute horizontal x coordinate for
* the mouse location
* @param yAbs the absolute vertical y coordinate for
* the mouse location
* @param clickCount the number of mouse clicks associated with the event
* @param popupTrigger a boolean value, true if this event is a trigger
* for a popup-menu
* @param scrollType the type of scrolling which should take place in
* response to this event; valid values are
* WHEEL_UNIT_SCROLL and
* WHEEL_BLOCK_SCROLL
* @param scrollAmount for scrollType WHEEL_UNIT_SCROLL,
* the number of units to be scrolled
* @param wheelRotation the integer number of "clicks" by which the mouse wheel
* was rotated
* @param preciseWheelRotation the double number of "clicks" by which the mouse wheel
* was rotated
*
* @throws IllegalArgumentException if source is null
* @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, boolean)
* @see MouseEvent#MouseEvent(java.awt.Component, int, long, int, int, int, int, int, int, boolean, int)
* @since 1.7
*/
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) {
super(source, id, when, modifiers, x, y, xAbs, yAbs, clickCount,
popupTrigger, MouseEvent.NOBUTTON);
this.scrollType = scrollType;
this.scrollAmount = scrollAmount;
this.wheelRotation = wheelRotation;
this.preciseWheelRotation = preciseWheelRotation;
}
/**
* Returns the type of scrolling that should take place in response to this
* event. This is determined by the native platform. Legal values are:
*
getScrollType returns
* MouseWheelEvent.WHEEL_UNIT_SCROLL
*
* @return number of units to scroll, or an undefined value if
* getScrollType returns
* MouseWheelEvent.WHEEL_BLOCK_SCROLL
* @see #getScrollType
*/
public int getScrollAmount() {
return scrollAmount;
}
/**
* 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.
*
* @return 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 user
* @see #getPreciseWheelRotation
*/
public int getWheelRotation() {
return wheelRotation;
}
/**
* 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".
*
* @return 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 user
* @see #getWheelRotation
* @since 1.7
*/
public double getPreciseWheelRotation() {
return preciseWheelRotation;
}
/**
* 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 ScrollPane and
* JScrollPane already have this functionality built in.)
*
* This method returns the number of units to scroll when scroll type is
* MouseWheelEvent.WHEEL_UNIT_SCROLL, and should only be called if
* getScrollType returns MouseWheelEvent.WHEEL_UNIT_SCROLL.
*
* 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);
* }
* }
*
*
* @return 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 platform
* @see #getScrollType
* @see #getScrollAmount
* @see MouseWheelListener
* @see java.awt.Adjustable
* @see java.awt.Adjustable#getUnitIncrement
* @see javax.swing.Scrollable
* @see javax.swing.Scrollable#getScrollableUnitIncrement
* @see java.awt.ScrollPane
* @see java.awt.ScrollPane#setWheelScrollingEnabled
* @see javax.swing.JScrollPane
* @see javax.swing.JScrollPane#setWheelScrollingEnabled
*/
public int getUnitsToScroll() {
return scrollAmount * wheelRotation;
}
/**
* Returns a parameter string identifying this event.
* This method is useful for event-logging and for debugging.
*
* @return a string identifying the event and its attributes
*/
public String paramString() {
String scrollTypeStr = null;
if (getScrollType() == WHEEL_UNIT_SCROLL) {
scrollTypeStr = "WHEEL_UNIT_SCROLL";
}
else if (getScrollType() == WHEEL_BLOCK_SCROLL) {
scrollTypeStr = "WHEEL_BLOCK_SCROLL";
}
else {
scrollTypeStr = "unknown scroll type";
}
return super.paramString()+",scrollType="+scrollTypeStr+
",scrollAmount="+getScrollAmount()+",wheelRotation="+
getWheelRotation()+",preciseWheelRotation="+getPreciseWheelRotation();
}
}