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UIKit Framework Reference UIAcceleration Class Reference

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UIAcceleration

Inherits From


Conforms To


Import Statement


Swift

import UIKit

Objective-C

@import UIKit;

Availability


Available in iOS 2.0 and later
Deprecated in iOS 5.0

An instance of the UIAcceleration class, called an acceleration event, represents immediate, three-dimensional acceleration data. To receive accelerometer events, register an application object as a delegate of the shared UIAccelerometer object, as described in UIAccelerometer Class Reference.

Each acceleration event includes simultaneous acceleration readings along the three axes of the device, as shown in Figure 1.

Figure 1Orientation of the device axes image: ../Art/device_axes.jpg

The device accelerometer reports values for each axis in units of g-force, where a value of 1.0 represents acceleration of about +1 g along a given axis. When a device is laying still with its back on a horizontal surface, each acceleration event has approximately the following values:

  • x: 0
  • y: 0
  • z: -1

Individual acceleration values are of type UIAccelerationValue, equivalent to a double. Values can range over the accelerations found in normal use of a device.

If you want to detect specific types of motion as gestures—specifically, shaking motions—use the UIEvent class and its UIEventTypeMotion event type. For details, see Motion Events in Event Handling Guide for iOS.

  • x x (iOS 5.0) Property

    The acceleration value for the x axis of the device. (read-only)

    Declaration

    Objective-C

    @property(nonatomic, readonly) UIAccelerationValue x

    Discussion

    With the device held in portrait orientation and the screen facing you, the x axis runs from left (negative values) to right (positive values) across the face of the device.

    Import Statement

    Objective-C

    @import UIKit;

    Availability

    Available in iOS 2.0 and later

    Deprecated in iOS 5.0

  • y y (iOS 5.0) Property

    The acceleration value for the y axis of the device. (read-only)

    Declaration

    Objective-C

    @property(nonatomic, readonly) UIAccelerationValue y

    Discussion

    With the device held in portrait orientation and the screen facing you, the y axis runs from bottom (negative values) to top (positive values) across the face of the device.

    Import Statement

    Objective-C

    @import UIKit;

    Availability

    Available in iOS 2.0 and later

    Deprecated in iOS 5.0

  • z z (iOS 5.0) Property

    The acceleration value for the z axis of the device. (read-only)

    Declaration

    Objective-C

    @property(nonatomic, readonly) UIAccelerationValue z

    Discussion

    With the device held in portrait orientation and the screen facing you, the z axis runs from back (negative values) to front (positive values) through the device.

    Import Statement

    Objective-C

    @import UIKit;

    Availability

    Available in iOS 2.0 and later

    Deprecated in iOS 5.0

  • timestamp timestamp (iOS 5.0) Property

    The relative time at which the acceleration event occurred. (read-only)

    Declaration

    Objective-C

    @property(nonatomic, readonly) NSTimeInterval timestamp

    Discussion

    This value indicates the time relative to the device CPU time base register. Compare acceleration event timestamps to determine the elapsed time between them. Do not use a timestamp to determine the exact time at which an event occurred.

    Import Statement

    Objective-C

    @import UIKit;

    Availability

    Available in iOS 2.0 and later

    Deprecated in iOS 5.0

Data Types

  • The amount of acceleration in a single linear direction.

    Declaration

    Swift

    typealias UIAccelerationValue = Double

    Objective-C

    typedef double UIAccelerationValue;

    Discussion

    This type is used to store acceleration values, which are specified as g-force values, where the value 1.0 corresponds to the normal acceleration caused by gravity at the Earth’s surface.

    Import Statement

    Objective-C

    @import UIKit;

    Swift

    import UIKit

    Availability

    Available in iOS 2.0 and later