Class

UIAcceleration

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.

Overview

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

Figure 1

Orientation of the device axes

Orientation of the device axes

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 Event Delivery: The Responder Chain in Event Handling Guide for iOS.

Symbols

Accessing the Acceleration Values

x

The acceleration value for the x axis of the device.

y

The acceleration value for the y axis of the device.

z

The acceleration value for the z axis of the device.

timestamp

The relative time at which the acceleration event occurred.

Constants

UIAccelerationValue

The amount of acceleration in a single linear direction.

Relationships

Inherits From