TouchEvent Class Reference

Inherits from
UIEvent : Event
Companion guide
Safari Web Content Guide
Availability
Available in iOS 2.0 and later.

Overview

The TouchEvent class encapsulates information about a touch event.

The system continually sends TouchEvent objects to an application as fingers touch and move across a surface. A touch event provides a snapshot of all touches during a multi-touch sequence, most importantly the touches that are new or have changed for a particular target. A multi-touch sequence begins when a finger first touches the surface. Other fingers may subsequently touch the surface, and all fingers may move across the surface. The sequence ends when the last of these fingers is lifted from the surface. An application receives touch event objects during each phase of any touch.

The different types of TouchEvent objects that can occur are:

touchstart

Sent when a finger for a given event touches the surface.

touchmove

Sent when a given event moves on the surface.

touchend

Sent when a given event lifts from the surface.

touchcancel

Sent when the system cancels tracking for the touch.

TouchEvent objects are combined together to form high-level GestureEvent objects that are also sent during a multi-touch sequence. See GestureEvent for details on GestureEvent objects and an example of the events sent for a two finger multi-touch gesture.

Tasks

Accessing Properties

Initializing

Properties

altKey

A Boolean value indicating whether the alt key is pressed.

readonly attribute boolean altKey
Discussion

If true, the alt key is pressed; otherwise, it is not. If there is no keyboard, this value is false.

Availability

changedTouches

A collection of Touch objects representing all touches that changed in this event.

readonly attribute TouchList changedTouches
Discussion

You manipulate this collection using TouchList methods.

Availability

ctrlKey

A Boolean value indicating whether the control key is pressed.

readonly attribute boolean ctrlKey
Discussion

If true, the control key is pressed; otherwise, it is not. If there is no keyboard, this value is false.

Availability

metaKey

A Boolean value indicating whether the meta key is pressed.

readonly attribute boolean metaKey
Discussion

If true, the meta key is pressed; otherwise, it is not. If there is no keyboard, this value is false.

Availability

rotation

The delta rotation since the start of an event in degrees where clockwise is positive and counter-clockwise is negative.

readonly attribute float rotation
Discussion

The initial value is 0.0.

Availability

scale

The distance between two fingers since the start of an event as a multiplier of the initial distance. 

readonly attribute float scale
Discussion

The initial value is 1.0. If less than 1.0 the gesture is pinch close to zoom out. If greater than 1.0 the gesture is pinch open to zoom in.

Availability

shiftKey

A Boolean value indicating whether the shift key is pressed.

readonly attribute boolean shiftKey
Discussion

If true, the shift key is pressed; otherwise, it is not. If there is no keyboard, this value is false.

Availability

targetTouches

A collection of Touch objects representing all touches associated with this target.

readonly attribute TouchList targetTouches
Availability

touches

A collection of Touch objects representing all touches associated with this event.

readonly attribute TouchList touches
Availability

Methods

initTouchEvent

Initializes a newly created TouchEvent object.

void initTouchEvent (in DOMString type, in boolean canBubble, in boolean cancelable, in DOMWindow view, in long detail, in long screenX, in long screenY, in long clientX, in long clientY, in boolean ctrlKey, in boolean altKey, in boolean shiftKey, in boolean metaKey, in TouchList touches, in TouchList targetTouches, in TouchList changedTouches, in float scale, in float rotation);
Parameters
type

The type of event that occurred.

canBubble

Indicates whether an event can bubble. If true, the event can bubble; otherwise, it cannot.

cancelable

Indicates whether an event can have its default action prevented. If true, the default action can be prevented; otherwise, it cannot.

view

The view (DOM window) in which the event occurred.

detail

Specifies some detail information about the event depending on the type of event.

screenX

The x-coordinate of the event’s location in screen coordinates.

screenY

The y-coordinate of the event’s location in screen coordinates.

clientX

The x-coordinate of the event’s location relative to the window’s viewport.

clientY

The y-coordinate of the event’s location relative to the window’s viewport.

ctrlKey

If true, the control key is pressed; otherwise, it is not.

altKey

If true, the alt key is pressed; otherwise, it is not.

shiftKey

If true, the shift key is pressed; otherwise, it is not.

metaKey

If true, the meta key is pressed; otherwise, it is not.

touches

A collection of Touch objects representing all touches associated with this event.

targetTouches

A collection of Touch objects representing all touches associated with this target.

changedTouches

A collection of Touch objects representing all touches that changed in this event.

scale

The distance between two fingers since the start of an event as a multiplier of the initial distance. The initial value is 1.0. If less than 1.0, the gesture is pinch close (to zoom out). If greater than 1.0, the gesture is pinch open (to zoom in).

rotation

The delta rotation since the start of an event, in degrees, where clockwise is positive and counter-clockwise is negative. The initial value is 0.0.

Discussion

Use this method to programmatically create a TouchEvent object.

Availability
  • Available in iOS 2.0 and later.


© 2010 Apple Inc. All Rights Reserved. (Last updated: 2010-12-16)

Did this document help you? Yes It's good, but... Not helpful...