Touch

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Touch 介面表示了一個於觸控裝置上接觸的單一觸碰點。觸碰點通常是由手指或觸控筆所接觸，而裝置可能為觸控螢幕或觸控板。

Touch.radiusX、Touch.radiusY 及 Touch.rotationAngle 描述了使用者與螢幕之間接觸的區域—觸碰區（touch area），這對處理不精確的指向設備（如手指）來說相當有幫助。這些數值被用來描述一個盡可能與整個接觸面積相匹配的橢圓（如使用者的指尖）。

Note: Many of the properties' values are hardware-dependent; for example, if the device doesn't have a way to detect the amount of pressure placed on the surface, the force value will always be 0. This may also be the case for radiusX and radiusY; if the hardware reports only a single point, these values will be 1.

建構式

Touch()
Creates a Touch object.

屬性

This interface has no parent, and doesn't inherits or implements any other property.

基本屬性

Touch.identifier Read only
Returns a unique identifier for this Touch object. A given touch point (say, by a finger) will have the same identifier for the duration of its movement around the surface. This lets you ensure that you're tracking the same touch all the time.
Touch.screenX Read only
Returns the X coordinate of the touch point relative to the left edge of the screen.
Touch.screenY Read only
Returns the Y coordinate of the touch point relative to the top edge of the screen.
Touch.clientX Read only
Returns the X coordinate of the touch point relative to the left edge of the browser viewport, not including any scroll offset.
Touch.clientY Read only
Returns the Y coordinate of the touch point relative to the top edge of the browser viewport, not including any scroll offset.
Touch.pageX Read only
Returns the X coordinate of the touch point relative to the left edge of the document. Unlike clientX, this value includes the horizontal scroll offset, if any.
Touch.pageY Read only
Returns the Y coordinate of the touch point relative to the top of the document. Unlike clientY, this value includes the vertical scroll offset, if any.
Touch.target Read only
Returns the Element on which the touch point started when it was first placed on the surface, even if the touch point has since moved outside the interactive area of that element or even been removed from the document.

觸碰區（Touch area）

這是一個實驗中的功能
此功能在某些瀏覽器尚在開發中，請參考兼容表格以得到不同瀏覽器用的前輟。

Touch.radiusX Read only
Returns the X radius of the ellipse that most closely circumscribes the area of contact with the screen. The value is in pixels of the same scale as screenX.
Touch.radiusY Read only
Returns the Y radius of the ellipse that most closely circumscribes the area of contact with the screen. The value is in pixels of the same scale as screenY.
Touch.rotationAngle Read only
Returns the angle (in degrees) that the ellipse described by radiusX and radiusY must be rotated, clockwise, to most accurately cover the area of contact between the user and the surface.
Touch.forceRead only
Returns the amount of pressure being applied to the surface by the user, as a float between 0.0 (no pressure) and 1.0 (maximum pressure).

方法

This interface has no method and no parent, and doesn't inherits or implements any method.

規範

Specification Status Comment
Touch Events – Level 2
The definition of 'Touch' in that specification.		 Draft Added radiusX, radiusY, rotationAngle, force properties, as well as the Touch() constructor.
Touch Events
The definition of 'Touch' in that specification.		 Recommendation Initial definition.

瀏覽器相容性

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!
Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 22.0 (Yes) 18.0 (18.0)[1]
52.0 (52.0)[2]		 No support No support No support
radiusX, radiusY, rotationAngle, force ? ? (Yes) ? ? ?
Touch() constructor ? No support No support ? ? ?
Feature Android Android Webview Chrome for Android Edge Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) 6.0 (6.0) (Yes) 11 (Yes) (Yes)
radiusX, radiusY, rotationAngle, force ? ? ? ? 6.0 (6.0) (Yes) ? ? ?
Touch() constructor ? ? No support ? No support No support ? ? ?

[1] Touch events were implemented in Gecko 18.0, but removed again in 24.0 (Firefox 24.0 / Thunderbird 24.0 / SeaMonkey 2.21) on the desktop version of Firefox due to web compatibility issues (bug 888304).

[2] As of Gecko 52.0, touch events support has been fixed and reenabled in Windows desktop platforms.

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