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## com.google.gwt.user.client
Class Event

    java.lang.Object
      com.google.gwt.core.client.JavaScriptObject
          com.google.gwt.user.client.Event

    public class Event

extends JavaScriptObject

An opaque handle to a native DOM Event. An `Event` cannot be created directly. Instead, use the `Event` type when returning a native DOM event from JSNI methods. An `Event` passed back into JSNI becomes the original DOM event the `Event` was created from, and can be accessed in JavaScript code as expected. This is typically done by calling methods in the `DOM` class.

### Event Attributes

In hosted mode, most accessors (eg. Event`getKeyCode()` and `getButton()`) assert that the requested attribute is reliable across all supported browsers. This means that attempting to retrieve an attribute for an `Event` that does not support that attribute will throw an `AssertionError`. For example, an `Event` of type `ONCLICK` will throw an `AssertionError` if you attempt to get the mouse button that was clicked using `getButton()` because the mouse button attribute is not defined for `ONCLICK` on Internet Explorer.

Field Summary
`static int` | `BUTTON_LEFT` The left mouse button (used in `DOM.eventGetButton(Event)`).
`static int` | `BUTTON_MIDDLE` The middle mouse button (used in `DOM.eventGetButton(Event)`).
`static int` | `BUTTON_RIGHT` The right mouse button (used in `DOM.eventGetButton(Event)`).
`static int` | `FOCUSEVENTS` A bit-mask covering both focus events (focus and blur).
`static int` | `KEYEVENTS` A bit-mask covering all keyboard events (down, up, and press).
`static int` | `MOUSEEVENTS` A bit-mask covering all mouse events (down, up, move, over, and out), but not click, dblclick, or wheel events.
`static int` | `ONBLUR` Fired when an element loses keyboard focus.
`static int` | `ONCHANGE` Fired when the value of an input element changes.
`static int` | `ONCLICK` Fired when the user clicks on an element.
`static int` | `ONCONTEXTMENU` Fired when the user requests an element's context menu (usually by right-clicking).
`static int` | `ONDBLCLICK` Fired when the user double-clicks on an element.
`static int` | `ONERROR` Fired when an image encounters an error.
`static int` | `ONFOCUS` Fired when an element receives keyboard focus.
`static int` | `ONKEYDOWN` Fired when the user depresses a key.
`static int` | `ONKEYPRESS` Fired when the a character is generated from a keypress (either directly or through auto-repeat).
`static int` | `ONKEYUP` Fired when the user releases a key.
`static int` | `ONLOAD` Fired when an element (normally an IMG) finishes loading.
`static int` | `ONLOSECAPTURE` Fired when an element that has mouse capture loses it.
`static int` | `ONMOUSEDOWN` Fired when the user depresses a mouse button over an element.
`static int` | `ONMOUSEMOVE` Fired when the mouse is moved within an element's area.
`static int` | `ONMOUSEOUT` Fired when the mouse is moved out of an element's area.
`static int` | `ONMOUSEOVER` Fired when the mouse is moved into an element's area.
`static int` | `ONMOUSEUP` Fired when the user releases a mouse button over an element.
`static int` | `ONMOUSEWHEEL` Fired when the user scrolls the mouse wheel over an element.
`static int` | `ONSCROLL` Fired when a scrollable element's scroll offset changes.
`static int` | `UNDEFINED` Deprecated.

Constructor Summary
`protected` | `Event()` Not directly instantiable.

Method Summary
`static void` | `addEventPreview(EventPreview preview)` Adds an event preview to the preview stack.
`void` | `cancelBubble(boolean cancel)` Cancels bubbling for the given event.
`boolean` | `getAltKey()` Gets whether the ALT key was depressed when the given event occurred.
`int` | `getButton()` Gets the mouse buttons that were depressed when the given event occurred.
`int` | `getClientX()` Gets the mouse x-position within the browser window's client area.
`int` | `getClientY()` Gets the mouse y-position within the browser window's client area.
`boolean` | `getCtrlKey()` Gets whether the CTRL key was depressed when the given event occurred.
`static Event` | `getCurrentEvent()` Gets the current event that is being fired.
`Element` | `getCurrentTarget()` Gets the current target element of this event.
`static int` | `getEventsSunk(Element elem)` Gets the current set of events sunk by a given element.
`Element` | `getFromElement()` Gets the element from which the mouse pointer was moved (only valid for `ONMOUSEOVER`).
`int` | `getKeyCode()` Gets the key code associated with this event.
`boolean` | `getMetaKey()` Gets whether the META key was depressed when the given event occurred.
`int` | `getMouseWheelVelocityY()` Gets the velocity of the mouse wheel associated with the event along the Y axis.
`boolean` | `getRepeat()` Gets the key-repeat state of this event.
`int` | `getScreenX()` Gets the mouse x-position on the user's display.
`int` | `getScreenY()` Gets the mouse y-position on the user's display.
`boolean` | `getShiftKey()` Gets whether the shift key was depressed when the given event occurred.
`java.lang.String` | `getString()` Gets a string representation of this event.
`Element` | `getTarget()` Returns the element that was the actual target of the given event.
`Element` | `getToElement()` Gets the element to which the mouse pointer was moved (only valid for `ONMOUSEOUT`).
`java.lang.String` | `getType()` Gets the enumerated type of this event (as defined in `Event`).
`int` | `getTypeInt()` Gets the enumerated type of this event, as defined by `ONCLICK`, `ONMOUSEDOWN`, and so forth.
`void` | `preventDefault()` Prevents the browser from taking its default action for the given event.
`static void` | `releaseCapture(Element elem)` Releases mouse capture on the given element.
`static void` | `removeEventPreview(EventPreview preview)` Removes an element from the preview stack.
`static void` | `setCapture(Element elem)` Sets mouse-capture on the given element.
`static void` | `sinkEvents(Element elem, int eventBits)` Sets the current set of events sunk by a given element.

Methods inherited from class com.google.gwt.core.client.JavaScriptObject
`cast, createArray, createFunction, createObject, equals, hashCode, toString`

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Field Detail

### BUTTON_LEFT

    public static final int BUTTON_LEFT

  The left mouse button (used in `DOM.eventGetButton(Event)`).

  See Also:
    Constant Field Values

### BUTTON_MIDDLE

    public static final int BUTTON_MIDDLE

  The middle mouse button (used in `DOM.eventGetButton(Event)`).

  See Also:
    Constant Field Values

### BUTTON_RIGHT

    public static final int BUTTON_RIGHT

  The right mouse button (used in `DOM.eventGetButton(Event)`).

  See Also:
    Constant Field Values

### ONBLUR

    public static final int ONBLUR

  Fired when an element loses keyboard focus.

  See Also:
    Constant Field Values

### ONCHANGE

    public static final int ONCHANGE

  Fired when the value of an input element changes.

  See Also:
    Constant Field Values

### ONCLICK

    public static final int ONCLICK

  Fired when the user clicks on an element.

  See Also:
    Constant Field Values

### ONDBLCLICK

    public static final int ONDBLCLICK

  Fired when the user double-clicks on an element.

  See Also:
    Constant Field Values

### ONERROR

    public static final int ONERROR

  Fired when an image encounters an error.

  See Also:
    Constant Field Values

### ONFOCUS

    public static final int ONFOCUS

  Fired when an element receives keyboard focus.

  See Also:
    Constant Field Values

### ONKEYDOWN

    public static final int ONKEYDOWN

  Fired when the user depresses a key.

  See Also:
    Constant Field Values

### ONKEYPRESS

    public static final int ONKEYPRESS

  Fired when the a character is generated from a keypress (either directly or through auto-repeat).

  See Also:
    Constant Field Values

### ONKEYUP

    public static final int ONKEYUP

  Fired when the user releases a key.

  See Also:
    Constant Field Values

### ONLOAD

    public static final int ONLOAD

  Fired when an element (normally an IMG) finishes loading.

  See Also:
    Constant Field Values

### ONLOSECAPTURE

    public static final int ONLOSECAPTURE

  Fired when an element that has mouse capture loses it.

  See Also:
    Constant Field Values

### ONMOUSEDOWN

    public static final int ONMOUSEDOWN

  Fired when the user depresses a mouse button over an element.

  See Also:
    Constant Field Values

### ONMOUSEMOVE

    public static final int ONMOUSEMOVE

  Fired when the mouse is moved within an element's area.

  See Also:
    Constant Field Values

### ONMOUSEOUT

    public static final int ONMOUSEOUT

  Fired when the mouse is moved out of an element's area.

  See Also:
    Constant Field Values

### ONMOUSEOVER

    public static final int ONMOUSEOVER

  Fired when the mouse is moved into an element's area.

  See Also:
    Constant Field Values

### ONMOUSEUP

    public static final int ONMOUSEUP

  Fired when the user releases a mouse button over an element.

  See Also:
    Constant Field Values

### ONMOUSEWHEEL

    public static final int ONMOUSEWHEEL

  Fired when the user scrolls the mouse wheel over an element.

  See Also:
    Constant Field Values

### ONSCROLL

    public static final int ONSCROLL

  Fired when a scrollable element's scroll offset changes.

  See Also:
    Constant Field Values

### ONCONTEXTMENU

    public static final int ONCONTEXTMENU

  Fired when the user requests an element's context menu (usually by right-clicking). Note that not all browsers will fire this event (notably Opera, as of 9.5).

  See Also:
    Constant Field Values

### FOCUSEVENTS

    public static final int FOCUSEVENTS

  A bit-mask covering both focus events (focus and blur).

  See Also:
    Constant Field Values

### KEYEVENTS

    public static final int KEYEVENTS

  A bit-mask covering all keyboard events (down, up, and press).

  See Also:
    Constant Field Values

### MOUSEEVENTS

    public static final int MOUSEEVENTS

  A bit-mask covering all mouse events (down, up, move, over, and out), but not click, dblclick, or wheel events.

  See Also:
    Constant Field Values

### UNDEFINED

    @Deprecated
    public static final int UNDEFINED

  Deprecated.
  Value returned by accessors when the actual integer value is undefined. In hosted mode, most accessors assert that the requested attribute is reliable across all supported browsers.

  See Also:
    `Event`, Constant Field Values

Constructor Detail

### Event

    protected Event()

  Not directly instantiable. Subclasses should also define a protected no-arg constructor to prevent client code from directly instantiating the class.

Method Detail

### addEventPreview

    public static void addEventPreview(EventPreview preview)

  Adds an event preview to the preview stack. As long as this preview remains on the top of the stack, it will receive all events before they are fired to their listeners. Note that the event preview will receive all events, including those received due to bubbling, whereas normal event handlers only receive explicitly sunk events.

  Parameters:
    `preview` - the event preview to be added to the stack.

### getCurrentEvent

    public static Event getCurrentEvent()

  Gets the current event that is being fired. The current event is only available within the lifetime of the onBrowserEvent function. Once the onBrowserEvent method returns, the current event is reset to null.

  Returns:
    the current event

### getEventsSunk

    public static int getEventsSunk(Element elem)

  Gets the current set of events sunk by a given element.

  Parameters:
    `elem` - the element whose events are to be retrieved
  Returns:
    a bitfield describing the events sunk on this element (its possible values are described in `Event`)

### releaseCapture

    public static void releaseCapture(Element elem)

  Releases mouse capture on the given element. Calling this method has no effect if the element does not currently have mouse capture.

  Parameters:
    `elem` - the element to release capture
  See Also:
    `setCapture(Element)`

### removeEventPreview

    public static void removeEventPreview(EventPreview preview)

  Removes an element from the preview stack. This element will no longer capture events, though any preview underneath it will begin to do so.

  Parameters:
    `preview` - the event preview to be removed from the stack

### setCapture

    public static void setCapture(Element elem)

  Sets mouse-capture on the given element. This element will directly receive all mouse events until `releaseCapture(Element)` is called on it.

  Parameters:
    `elem` - the element on which to set mouse capture

### sinkEvents

    public static void sinkEvents(Element elem,
                                  int eventBits)

  Sets the current set of events sunk by a given element. These events will be fired to the nearest `EventListener` specified on any of the element's parents.

  Parameters:
    `elem` - the element whose events are to be retrieved
    `eventBits` - a bitfield describing the events sunk on this element (its possible values are described in `Event`)

### cancelBubble

    public final void cancelBubble(boolean cancel)

  Cancels bubbling for the given event. This will stop the event from being propagated to parent elements.

  Parameters:
    `cancel` - `true` to cancel bubbling

### getAltKey

    public final boolean getAltKey()
                            throws java.lang.AssertionError

  Gets whether the ALT key was depressed when the given event occurred.

  Returns:
    `true` if ALT was depressed when the event occurred
  Throws:
    `java.lang.AssertionError` - if event type is not one of `MOUSEEVENTS`, `ONCLICK`, `ONDBLCLICK`, `KEYEVENTS`, or `ONCONTEXTMENU`

### getButton

    public final int getButton()
                        throws java.lang.AssertionError

  Gets the mouse buttons that were depressed when the given event occurred.

  Returns:
    a bit-field, defined by `BUTTON_LEFT`, `BUTTON_MIDDLE`, and `BUTTON_RIGHT`
  Throws:
    `java.lang.AssertionError` - if event type is not one of `ONMOUSEDOWN` or `ONMOUSEUP`

### getClientX

    public final int getClientX()
                         throws java.lang.AssertionError

  Gets the mouse x-position within the browser window's client area.

  Returns:
    the mouse x-position
  Throws:
    `java.lang.AssertionError` - if event type is not one of `MOUSEEVENTS`, `ONCLICK`, `ONDBLCLICK`, `ONMOUSEWHEEL`, or `ONCONTEXTMENU`

### getClientY

    public final int getClientY()
                         throws java.lang.AssertionError

  Gets the mouse y-position within the browser window's client area.

  Returns:
    the mouse y-position
  Throws:
    `java.lang.AssertionError` - if event type is not one of `MOUSEEVENTS`, `ONCLICK`, `ONDBLCLICK`, `ONMOUSEWHEEL`, or `ONCONTEXTMENU`

### getCtrlKey

    public final boolean getCtrlKey()
                             throws java.lang.AssertionError

  Gets whether the CTRL key was depressed when the given event occurred.

  Returns:
    `true` if CTRL was depressed when the event occurred
  Throws:
    `java.lang.AssertionError` - if event type is not one of `MOUSEEVENTS`, `ONCLICK`, `ONDBLCLICK`, `KEYEVENTS`, or `ONCONTEXTMENU`

### getCurrentTarget

    public final Element getCurrentTarget()

  Gets the current target element of this event. This is the element whose listener fired last, not the element which fired the event initially.

  Returns:
    the event's current target element

### getFromElement

    public final Element getFromElement()
                                 throws java.lang.AssertionError

  Gets the element from which the mouse pointer was moved (only valid for `ONMOUSEOVER`).

  Returns:
    the element from which the mouse pointer was moved
  Throws:
    `java.lang.AssertionError` - if event type is not one of `ONMOUSEOVER` or `ONMOUSEOUT`

### getKeyCode

    public final int getKeyCode()
                         throws java.lang.AssertionError

  Gets the key code associated with this event.

  For `ONKEYPRESS`, this method returns the Unicode value of the character generated. For `ONKEYDOWN` and `ONKEYUP`, it returns the code associated with the physical key.

  Returns:
    the Unicode character or key code.
  Throws:
    `java.lang.AssertionError` - if event type is not one of `KEYEVENTS`
  See Also:
    `KeyboardListener`

### getMetaKey

    public final boolean getMetaKey()
                             throws java.lang.AssertionError

  Gets whether the META key was depressed when the given event occurred.

  Returns:
    `true` if META was depressed when the event occurred
  Throws:
    `java.lang.AssertionError` - if event type is not one of `MOUSEEVENTS`, `ONCLICK`, `ONDBLCLICK`, `KEYEVENTS`, or `ONCONTEXTMENU`

### getMouseWheelVelocityY

    public final int getMouseWheelVelocityY()
                                     throws java.lang.AssertionError

  Gets the velocity of the mouse wheel associated with the event along the Y axis.

  The velocity of the event is an artifical measurement for relative comparisons of wheel activity. It is affected by some non-browser factors, including choice of input hardware and mouse acceleration settings. The sign of the velocity measurement agrees with the screen coordinate system; negative values are towards the origin and positive values are away from the origin. Standard scrolling speed is approximately ten units per event.

  Returns:
    The velocity of the mouse wheel.
  Throws:
    `java.lang.AssertionError` - if event type is not `ONMOUSEWHEEL`

### getRepeat

    public final boolean getRepeat()
                            throws java.lang.AssertionError

  Gets the key-repeat state of this event.

  Returns:
    `true` if this key event was an auto-repeat
  Throws:
    `java.lang.AssertionError` - if event type is not `ONKEYDOWN`

### getScreenX

    public final int getScreenX()
                         throws java.lang.AssertionError

  Gets the mouse x-position on the user's display.

  Returns:
    the mouse x-position
  Throws:
    `java.lang.AssertionError` - if event type is not one of `MOUSEEVENTS`, `ONMOUSEWHEEL`, `ONCLICK`, `ONDBLCLICK`, or `ONCONTEXTMENU`

### getScreenY

    public final int getScreenY()
                         throws java.lang.AssertionError

  Gets the mouse y-position on the user's display.

  Returns:
    the mouse y-position
  Throws:
    `java.lang.AssertionError` - if event type is not one of `MOUSEEVENTS`, `ONMOUSEWHEEL`, `ONCLICK`, `ONDBLCLICK`, or `ONCONTEXTMENU`

### getShiftKey

    public final boolean getShiftKey()
                              throws java.lang.AssertionError

  Gets whether the shift key was depressed when the given event occurred.

  Returns:
    `true` if shift was depressed when the event occurred
  Throws:
    `java.lang.AssertionError` - if event type is not one of `MOUSEEVENTS`, `ONCLICK`, `ONDBLCLICK`, `KEYEVENTS`, or `ONCONTEXTMENU`

### getString

    public final java.lang.String getString()

  Gets a string representation of this event. We do not override `JavaScriptObject.toString()` because it is final in `JavaScriptObject`.

  Returns:
    the string representation of this event

### getTarget

    public final Element getTarget()

  Returns the element that was the actual target of the given event.

  Returns:
    the target element

### getToElement

    public final Element getToElement()
                               throws java.lang.AssertionError

  Gets the element to which the mouse pointer was moved (only valid for `ONMOUSEOUT`).

  Returns:
    the element to which the mouse pointer was moved
  Throws:
    `java.lang.AssertionError` - if event type is not one of `ONMOUSEOVER` or `ONMOUSEOUT`

### getType

    public final java.lang.String getType()

  Gets the enumerated type of this event (as defined in `Event`).

  Returns:
    the event's enumerated type

### getTypeInt

    public final int getTypeInt()

  Gets the enumerated type of this event, as defined by `ONCLICK`, `ONMOUSEDOWN`, and so forth.

  Returns:
    the event's enumerated type

### preventDefault

    public final void preventDefault()

  Prevents the browser from taking its default action for the given event.

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