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.

Constructs a MouseWheelEvent object with the specified source component, type, modifiers, 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.

Parameters
sourcethe Component that originated the event
idthe integer that identifies the event
whena long that gives the time the event occurred
modifiersthe modifier keys down during event (shift, ctrl, alt, meta)
xthe horizontal x coordinate for the mouse location
ythe vertical y coordinate for the mouse location
clickCountthe number of mouse clicks associated with event
popupTriggera boolean, true if this event is a trigger for a popup-menu
scrollTypethe type of scrolling which should take place in response to this event; valid values are WHEEL_UNIT_SCROLL and WHEEL_BLOCK_SCROLL
scrollAmountfor scrollType WHEEL_UNIT_SCROLL, the number of units to be scrolled
wheelRotationthe amount that the mouse wheel was rotated (the number of "clicks")
Throws
IllegalArgumentExceptionif source is null
The event mask for selecting action events.
The event mask for selecting adjustment events.
The Alt key extended modifier constant.
@since
1.4
The AltGraph key extended modifier constant.
@since
1.4
The AltGraph key modifier constant.
The Alt key modifier constant. It is recommended that ALT_DOWN_MASK be used instead.
Indicates mouse button #1; used by #getButton .
@since
1.4
The Mouse Button1 extended modifier constant.
@since
1.4
The Mouse Button1 modifier constant. It is recommended that BUTTON1_DOWN_MASK be used instead.
Indicates mouse button #2; used by #getButton .
@since
1.4
The Mouse Button2 extended modifier constant.
@since
1.4
The Mouse Button2 modifier constant. It is recommended that BUTTON2_DOWN_MASK be used instead. Note that BUTTON2_MASK has the same value as ALT_MASK.
Indicates mouse button #3; used by #getButton .
@since
1.4
The Mouse Button3 extended modifier constant.
@since
1.4
The Mouse Button3 modifier constant. It is recommended that BUTTON3_DOWN_MASK be used instead. Note that BUTTON3_MASK has the same value as META_MASK.
The event mask for selecting component events.
The first number in the range of ids used for component events.
This event indicates that the component was rendered invisible.
The last number in the range of ids used for component events.
This event indicates that the component's position changed.
This event indicates that the component's size changed.
This event indicates that the component was made visible.
The event mask for selecting container events.
The Control key extended modifier constant.
@since
1.4
The Control key modifier constant. It is recommended that CTRL_DOWN_MASK be used instead.
The event mask for selecting focus events.
The event mask for selecting hierarchy bounds events.
The event mask for selecting hierarchy events.
The event mask for selecting input method events.
The event mask for selecting invocation events.
The event mask for selecting item events.
The event mask for selecting key events.
The Meta key extended modifier constant.
@since
1.4
The Meta key modifier constant. It is recommended that META_DOWN_MASK be used instead.
The "mouse clicked" event. This MouseEvent occurs when a mouse button is pressed and released.
The "mouse dragged" event. This MouseEvent occurs when the mouse position changes while a mouse button is pressed.
The "mouse entered" event. This MouseEvent occurs when the mouse cursor enters the unobscured part of component's geometry.
The event mask for selecting mouse events.
The "mouse exited" event. This MouseEvent occurs when the mouse cursor exits the unobscured part of component's geometry.
The first number in the range of ids used for mouse events.
The last number in the range of ids used for mouse events.
The event mask for selecting mouse motion events.
The "mouse moved" event. This MouseEvent occurs when the mouse position changes.
The "mouse pressed" event. This MouseEvent occurs when a mouse button is pushed down.
The "mouse released" event. This MouseEvent occurs when a mouse button is let up.
The "mouse wheel" event. This is the only MouseWheelEvent. It occurs when a mouse equipped with a wheel has its wheel rotated.
@since
1.4
The event mask for selecting mouse wheel events.
@since
1.4
Indicates no mouse buttons; used by #getButton .
@since
1.4
The event mask for selecting paint events.
The maximum value for reserved AWT event IDs. Programs defining their own event IDs should use IDs greater than this value.
The Shift key extended modifier constant.
@since
1.4
The Shift key modifier constant. It is recommended that SHIFT_DOWN_MASK be used instead.
The event mask for selecting text events.
Constant representing scrolling by a "block" (like scrolling with page-up, page-down keys)
Constant representing scrolling by "units" (like scrolling with the arrow keys)
The event mask for selecting window events.
The event mask for selecting window focus events.
@since
1.4
The event mask for selecting window state events.
@since
1.4
Consumes this event so that it will not be processed in the default manner by the source which originated it.
Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

  • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
  • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
  • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
  • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
  • For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Parameters
objthe reference object with which to compare.
Return
true if this object is the same as the obj argument; false otherwise.
Returns which, if any, of the mouse buttons has changed state.
Return
one of the following constants: NOBUTTON, BUTTON1, BUTTON2 or BUTTON3.
@since
1.4
Returns the runtime class of an object. That Class object is the object that is locked by static synchronized methods of the represented class.
Return
The java.lang.Class object that represents the runtime class of the object. The result is of type {@code Class} where X is the erasure of the static type of the expression on which getClass is called.
Returns the number of mouse clicks associated with this event.
Return
integer value for the number of clicks
Returns the originator of the event.
Return
the Component object that originated the event, or null if the object is not a Component.
Returns the event type.
Returns the modifier mask for this event.
Returns the extended modifier mask for this event. Extended modifiers represent the state of all modal keys, such as ALT, CTRL, META, and the mouse buttons just after the event occurred

For example, if the user presses button 1 followed by button 2, and then releases them in the same order, the following sequence of events is generated:

    MOUSE_PRESSED:  BUTTON1_DOWN_MASK
    MOUSE_PRESSED:  BUTTON1_DOWN_MASK | BUTTON2_DOWN_MASK
    MOUSE_RELEASED: BUTTON2_DOWN_MASK
    MOUSE_CLICKED:  BUTTON2_DOWN_MASK
    MOUSE_RELEASED: 
    MOUSE_CLICKED:  
 

It is not recommended to compare the return value of this method using == because new modifiers can be added in the future. For example, the appropriate way to check that SHIFT and BUTTON1 are down, but CTRL is up is demonstrated by the following code:

    int onmask = SHIFT_DOWN_MASK | BUTTON1_DOWN_MASK;
    int offmask = CTRL_DOWN_MASK;
    if (event.getModifiersEx() & (onmask | offmask) == onmask) {
        ...
    }
 
The above code will work even if new modifiers are added.
@since
1.4
Returns a String describing the extended modifier keys and mouse buttons, such as "Shift", "Button1", or "Ctrl+Shift". These strings can be localized by changing the awt.properties file.
Parameters
modifiersa modifier mask describing the extended modifier keys and mouse buttons for the event
Return
a text description of the combination of extended modifier keys and mouse buttons that were held down during the event.
@since
1.4
Returns a String describing the modifier keys and mouse buttons that were down during the event, such as "Shift", or "Ctrl+Shift". These strings can be localized by changing the awt.properties file.

Note that InputEvent.ALT_MASK and InputEvent.BUTTON2_MASK have the same value, so the string "Alt" is returned for both modifiers. Likewise, InputEvent.META_MASK and InputEvent.BUTTON3_MASK have the same value, so the string "Meta" is returned for both modifiers.

Parameters
modifiersa modifier mask describing the modifier keys and mouse buttons that were down during the event
Return
string a text description of the combination of modifier keys and mouse buttons that were down during the event
@since
1.4
Returns the x,y position of the event relative to the source component.
Return
a Point object containing the x and y coordinates relative to the source component
Returns the number of units that should be scrolled in response to this event. Only valid if getScrollType returns MouseWheelEvent.WHEEL_UNIT_SCROLL
Return
number of units to scroll, or an undefined value if getScrollType returns MouseWheelEvent.WHEEL_BLOCK_SCROLL
Returns the type of scrolling that should take place in response to this event. This is determined by the native platform. Legal values are:
  • MouseWheelEvent.WHEEL_UNIT_SCROLL
  • MouseWheelEvent.WHEEL_BLOCK_SCROLL
Return
either MouseWheelEvent.WHEEL_UNIT_SCROLL or MouseWheelEvent.WHEEL_BLOCK_SCROLL, depending on the configuration of the native platform.
The object on which the Event initially occurred.
Return
The object on which the Event initially occurred.
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);
      }
  }
 
Returns the number of "clicks" the mouse wheel was rotated.
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
Returns the timestamp of when this event occurred.
Returns the horizontal x position of the event relative to the source component.
Return
x an integer indicating horizontal position relative to the component
Returns the vertical y position of the event relative to the source component.
Return
y an integer indicating vertical position relative to the component
Returns a hash code value for the object. This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable.

The general contract of hashCode is:

  • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
  • If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
  • It is not required that if two objects are unequal according to the method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hashtables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the JavaTM programming language.)

Return
a hash code value for this object.
Returns whether or not the Alt modifier is down on this event.
Returns whether or not the AltGraph modifier is down on this event.
Returns whether or not this event has been consumed.
See Also
Returns whether or not the Control modifier is down on this event.
Returns whether or not the Meta modifier is down on this event.
Returns whether or not this mouse event is the popup menu trigger event for the platform.

Note: Popup menus are triggered differently on different systems. Therefore, isPopupTrigger should be checked in both mousePressed and mouseReleased for proper cross-platform functionality.

Return
boolean, true if this event is the popup menu trigger for this platform
Returns whether or not the Shift modifier is down on this event.
Wakes up a single thread that is waiting on this object's monitor. If any threads are waiting on this object, one of them is chosen to be awakened. The choice is arbitrary and occurs at the discretion of the implementation. A thread waits on an object's monitor by calling one of the wait methods.

The awakened thread will not be able to proceed until the current thread relinquishes the lock on this object. The awakened thread will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened thread enjoys no reliable privilege or disadvantage in being the next thread to lock this object.

This method should only be called by a thread that is the owner of this object's monitor. A thread becomes the owner of the object's monitor in one of three ways:

  • By executing a synchronized instance method of that object.
  • By executing the body of a synchronized statement that synchronizes on the object.
  • For objects of type Class, by executing a synchronized static method of that class.

Only one thread at a time can own an object's monitor.

Throws
IllegalMonitorStateExceptionif the current thread is not the owner of this object's monitor.
Wakes up all threads that are waiting on this object's monitor. A thread waits on an object's monitor by calling one of the wait methods.

The awakened threads will not be able to proceed until the current thread relinquishes the lock on this object. The awakened threads will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened threads enjoy no reliable privilege or disadvantage in being the next thread to lock this object.

This method should only be called by a thread that is the owner of this object's monitor. See the notify method for a description of the ways in which a thread can become the owner of a monitor.

Throws
IllegalMonitorStateExceptionif the current thread is not the owner of this object's monitor.
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
Retargets an event to a new source. This method is typically used to retarget an event to a lightweight child Component of the original heavyweight source.

This method is intended to be used only by event targeting subsystems, such as client-defined KeyboardFocusManagers. It is not for general client use.

Parameters
newSourcethe new Object to which the event should be dispatched
Returns a String representation of this object.
Translates the event's coordinates to a new position by adding specified x (horizontal) and y (vertical) offsets.
Parameters
xthe horizontal x value to add to the current x coordinate position
ythe vertical y value to add to the current y coordinate position
Causes current thread to wait until another thread invokes the method or the method for this object. In other words, this method behaves exactly as if it simply performs the call wait(0).

The current thread must own this object's monitor. The thread releases ownership of this monitor and waits until another thread notifies threads waiting on this object's monitor to wake up either through a call to the notify method or the notifyAll method. The thread then waits until it can re-obtain ownership of the monitor and resumes execution.

As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:

     synchronized (obj) {
         while (<condition does not hold>)
             obj.wait();
         ... // Perform action appropriate to condition
     }
 
This method should only be called by a thread that is the owner of this object's monitor. See the notify method for a description of the ways in which a thread can become the owner of a monitor.
Throws
IllegalMonitorStateExceptionif the current thread is not the owner of the object's monitor.
InterruptedExceptionif another thread interrupted the current thread before or while the current thread was waiting for a notification. The interrupted status of the current thread is cleared when this exception is thrown.
Causes current thread to wait until either another thread invokes the method or the method for this object, or a specified amount of time has elapsed.

The current thread must own this object's monitor.

This method causes the current thread (call it T) to place itself in the wait set for this object and then to relinquish any and all synchronization claims on this object. Thread T becomes disabled for thread scheduling purposes and lies dormant until one of four things happens:

  • Some other thread invokes the notify method for this object and thread T happens to be arbitrarily chosen as the thread to be awakened.
  • Some other thread invokes the notifyAll method for this object.
  • Some other thread interrupts thread T.
  • The specified amount of real time has elapsed, more or less. If timeout is zero, however, then real time is not taken into consideration and the thread simply waits until notified.
The thread T is then removed from the wait set for this object and re-enabled for thread scheduling. It then competes in the usual manner with other threads for the right to synchronize on the object; once it has gained control of the object, all its synchronization claims on the object are restored to the status quo ante - that is, to the situation as of the time that the wait method was invoked. Thread T then returns from the invocation of the wait method. Thus, on return from the wait method, the synchronization state of the object and of thread T is exactly as it was when the wait method was invoked.

A thread can also wake up without being notified, interrupted, or timing out, a so-called spurious wakeup. While this will rarely occur in practice, applications must guard against it by testing for the condition that should have caused the thread to be awakened, and continuing to wait if the condition is not satisfied. In other words, waits should always occur in loops, like this one:

     synchronized (obj) {
         while (<condition does not hold>)
             obj.wait(timeout);
         ... // Perform action appropriate to condition
     }
 
(For more information on this topic, see Section 3.2.3 in Doug Lea's "Concurrent Programming in Java (Second Edition)" (Addison-Wesley, 2000), or Item 50 in Joshua Bloch's "Effective Java Programming Language Guide" (Addison-Wesley, 2001).

If the current thread is interrupted by another thread while it is waiting, then an InterruptedException is thrown. This exception is not thrown until the lock status of this object has been restored as described above.

Note that the wait method, as it places the current thread into the wait set for this object, unlocks only this object; any other objects on which the current thread may be synchronized remain locked while the thread waits.

This method should only be called by a thread that is the owner of this object's monitor. See the notify method for a description of the ways in which a thread can become the owner of a monitor.

Parameters
timeoutthe maximum time to wait in milliseconds.
Throws
IllegalArgumentExceptionif the value of timeout is negative.
IllegalMonitorStateExceptionif the current thread is not the owner of the object's monitor.
InterruptedExceptionif another thread interrupted the current thread before or while the current thread was waiting for a notification. The interrupted status of the current thread is cleared when this exception is thrown.
Causes current thread to wait until another thread invokes the method or the method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.

This method is similar to the wait method of one argument, but it allows finer control over the amount of time to wait for a notification before giving up. The amount of real time, measured in nanoseconds, is given by:

 1000000*timeout+nanos

In all other respects, this method does the same thing as the method of one argument. In particular, wait(0, 0) means the same thing as wait(0).

The current thread must own this object's monitor. The thread releases ownership of this monitor and waits until either of the following two conditions has occurred:

  • Another thread notifies threads waiting on this object's monitor to wake up either through a call to the notify method or the notifyAll method.
  • The timeout period, specified by timeout milliseconds plus nanos nanoseconds arguments, has elapsed.

The thread then waits until it can re-obtain ownership of the monitor and resumes execution.

As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:

     synchronized (obj) {
         while (<condition does not hold>)
             obj.wait(timeout, nanos);
         ... // Perform action appropriate to condition
     }
 
This method should only be called by a thread that is the owner of this object's monitor. See the notify method for a description of the ways in which a thread can become the owner of a monitor.
Parameters
timeoutthe maximum time to wait in milliseconds.
nanosadditional time, in nanoseconds range 0-999999.
Throws
IllegalArgumentExceptionif the value of timeout is negative or the value of nanos is not in the range 0-999999.
IllegalMonitorStateExceptionif the current thread is not the owner of this object's monitor.
InterruptedExceptionif another thread interrupted the current thread before or while the current thread was waiting for a notification. The interrupted status of the current thread is cleared when this exception is thrown.