com.smartgwt.client.util
Class EventHandler

java.lang.Object
  com.smartgwt.client.util.EventHandler

public class EventHandler
extends java.lang.Object

The ISC system provides a predictable cross-browser event-handling mechanism for ISC widgets. Events can be handled both at the page level (i.e., globally), and at the level of individual widgets.

With the exception of a few page-specific events ('load', 'unload', 'idle' and 'resize'), events are processed in the following sequence:

1. The event is sent to any global (page-level) event handlers. These handlers can cancel further propagation of the event by returning false. You can register to listen for any of the events linked in the seeAlso section (below) by calling Page.setEvent method.

2. If the event occurred on a form element or a link, it is passed on to the browser so that the element will perform its default action. No widget receives the event.

3. If the event occurred on an enabled widget (but not on a form element or link inside the widget), it is sent to that widget's event handler, if any. This handler can cancel further propagation of the event by returning false. An "enabled" widget is any widget that defines an event handler for one of the supported events. Interceptable events are defined in the "widgetEvents" section of Canvas.

4. The event is "bubbled" up to the widget's parent in the containment hierarchy, if any. Again, the parent's handler for the event can cancel further propagation by returning false. This step is repeated, with the event "bubbling" up through the containment hierarchy, until a top-level widget is reached or the event is explicitly canceled. In brief, the ISC event model offers the best features of browser event models:

• Page-first event handling allows you to reliably process or cancel any event before it affects the objects on the page.
• Event "bubbling" ensures that parent widgets receive events sent to their children, and allows you to create generalized parent-level handlers rather than duplicating code in each child.

Note: Canceling propagation of an event may cancel its side effects as well, including the generation of other (synthetic) events. For example, if a global mouseDown handler returns false, drag-and-drop events will not be generated. Specific effects are discussed in the descriptions of the various events in the following sections.

Smart GWT libraries will not interfere with native event handling when events occur outside of a target widget. You can therefore have HTML that is not ISC-based on the same page as widget objects that will react to native events as you would expect.

You can use isc.Event as an alias for isc.EventHandler.

See Also:

PageEvent, com.smartgwt.client.util.Page#setEvent, com.smartgwt.client.util.Page#clearEvent

Constructor Summary

EventHandler()

Method Summary

static java.lang.Boolean	altKeyDown() Return true if the alt (option) key is being held down.
static java.lang.Boolean	ctrlKeyDown() Return true if the control key is being held down.
static Rectangle	getDragRect() During a drag with dragAppearance of either "target" or "outline", returns the page-relative coordinates of whatever element is being dragged.
static Canvas	getDragTarget() Returns the current dragTarget.
static java.lang.String	getKey() Return the name of the key for the event passed in.
static java.lang.String	getKeyEventCharacter() Return the character for the current key being pressed.
static int	getKeyEventCharacterValue() Returns the numeric characterValue reported by the browser.
static java.lang.Integer	getMouseDownX() Return the page-relative X (horizontal) coordinate of an event.
static java.lang.Integer	getMouseDownY() Return the page-relative Y (vertical) coordinate of an event.
static Element	getNativeMouseTarget() Returns the natively reported target (or source) DOM element for the current mouse event.
static Canvas	getTarget() Return the canvas that is the target of the mouse event.
static int	getWheelDelta() Applies to mouseWheel events only.
static int	getX() Return the page-relative X (horizontal) coordinate of an event.
static int	getY() Return the page-relative Y (vertical) coordinate of an event.
static java.lang.Boolean	leftButtonDown() Returns true if the left mouse button is being pressed.
static java.lang.Boolean	rightButtonDown() Returns true if the right mouse button is being pressed.
static void	setDragTracker(java.lang.String html) Set the HTML for the drag tracker that follows the mouse during a drag and drop interaction.
static void	setDragTracker(java.lang.String html, int newWidth, int newHeight, int offsetX, int offsetY) Set the HTML for the drag tracker that follows the mouse during a drag and drop interaction.
static java.lang.Boolean	shiftKeyDown() Return true if the shift key is being held down.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EventHandler

public EventHandler()

Method Detail

altKeyDown

public static java.lang.Boolean altKeyDown()

Return true if the alt (option) key is being held down. Note that this is only set reliably for keyboard events.

Returns:

true == alt key is down

ctrlKeyDown

public static java.lang.Boolean ctrlKeyDown()

Return true if the control key is being held down. Note that this is only set reliably for keyboard events.

Returns:

true == control key is down

getDragTarget

public static Canvas getDragTarget()

Returns the current dragTarget. This is the component on which the drag and drop interaction was initiated. This only returns something meaningful during a drag and drop interaction.

Returns:

The dragTarget.

See Also:

Canvas.getDragTarget()

getKeyEventCharacter

public static java.lang.String getKeyEventCharacter()

Return the character for the current key being pressed. Note that this is only set reliably for keyPress events on character keys.

Returns:

Character the user entered. May be null for non-character keys.

getKeyEventCharacterValue

public static int getKeyEventCharacterValue()

Returns the numeric characterValue reported by the browser. Only available on keyPress events, and only for character (or ascii control) keys

Returns:

Numeric character value reported by the browser (ASCII value of the key pressed)

getNativeMouseTarget

public static Element getNativeMouseTarget()

Returns the natively reported target (or source) DOM element for the current mouse event. NOTE: Smart GWT cannot guarantee that the same element will be reported in all browser/platform configurations for all event types. If you wish to make use of this value, we recommend testing your use case in all target browser configurations.

Returns:

native DOM element over which the mouse event occurred

getTarget

public static Canvas getTarget()

Return the canvas that is the target of the mouse event. Returns null if no canvas found.

Returns:

event target canvas

getWheelDelta

public static int getWheelDelta()

Applies to mouseWheel events only. Returns an integer indicating how far the mouse wheel was rotated. This value will be positive if the user scrolled the mousewheel forward or up, or negative if scrolled in the other direction and will be a multiple of 1 where 1 indicates the smallest possible rotation of the wheel.

Returns:

integer indicating how far the mouse wheel was rotated.

getX

public static int getX()

Return the page-relative X (horizontal) coordinate of an event.

Returns:

x-coordinate in page coordinate space

getY

public static int getY()

Return the page-relative Y (vertical) coordinate of an event.

Returns:

y-coordinate in page coordinate space

leftButtonDown

public static java.lang.Boolean leftButtonDown()

Returns true if the left mouse button is being pressed.

Returns:

true == left button is down, false == up

rightButtonDown

public static java.lang.Boolean rightButtonDown()

Returns true if the right mouse button is being pressed.

Returns:

true == right button is down, false == up

shiftKeyDown

public static java.lang.Boolean shiftKeyDown()

Return true if the shift key is being held down. Note that this is only set reliably for keyboard events.

Returns:

true == shift key is down

setDragTracker

public static void setDragTracker(java.lang.String html)

Set the HTML for the drag tracker that follows the mouse during a drag and drop interaction.

Your canvas can use this routine to set the drag tracker to whatever HTML you want like so:

    dragStart : function
 () {        isc.EventHandler.setDragTracker('Your contents here');    } 

Parameters:

html - HTML for the tracker

setDragTracker

public static void setDragTracker(java.lang.String html,
                                  int newWidth,
                                  int newHeight,
                                  int offsetX,
                                  int offsetY)

Set the HTML for the drag tracker that follows the mouse during a drag and drop interaction.

Your canvas can use this routine to set the drag tracker to whatever HTML you want like so:

    dragStart : function
 () {        isc.EventHandler.setDragTracker('Your contents here');    } 

Parameters:

html - HTML for the tracker

newWidth - new width for the tracker

newHeight - new height for the tracker

offsetX - x-offset for the tracker

offsetY - y-offset for the tracker

getDragRect

public static Rectangle getDragRect()

During a drag with dragAppearance of either "target" or "outline", returns the page-relative coordinates of whatever element is being dragged. Calling this method allows you to write drag and drop logic that works identically even if dragAppearance is subsequently changed.

Returns:

lobal (page-relative) coordinates and size of the dragged element, as a 4-element array [left,top,width,height], or null if not dragging

getMouseDownX

public static java.lang.Integer getMouseDownX()

Return the page-relative X (horizontal) coordinate of an event.

Returns:

x-coordinate in page coordinate space

getMouseDownY

public static java.lang.Integer getMouseDownY()

Return the page-relative Y (vertical) coordinate of an event.

Returns:

y-coordinate in page coordinate space

getKey

public static java.lang.String getKey()

Return the name of the key for the event passed in. Note that this is only set reliably for keyboard events.

 Strings to identify the various keys on the keyboard.

 For alpha keys, the single (uppercase) character value is used, such as "Q"
 For Numeric keys, the number is used as in a single character string, like "1"
 Function keys are identified as "f1" - "f12"
 Non alpha-numeric character keys (such as the key for "[" / "{") are identified by their unmodified character value (the value obtained by hitting the key without holding shift down), by default - exceptions are listed below.
 Additional key names:
 - Space
 - Tab
 - Enter
 - Escape
 - Backspace
 - Insert
 - Delete
 - Arrow_Up
 - Arrow_Down
 - Arrow_Left
 - Arrow_Right
 - Home
 - End
 - Page_Up
 - Page_Down
 - Shift
 - Ctrl
 - Alt
 [Note: Some keys may not be available for capture on every platform]
 

Returns:

the key name

See Also:

KeyNames