javascript 获取当前元素上的touchstart坐标
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get touchstart coordinate on current element
提问by h4lc0n
So I have an element that looks like this:
所以我有一个看起来像这样的元素：
____________________________________
/ \
| |
| |
+------------------------------------+
| |
| |
| |
+------------------------------------+
| |
| |
\____________________________________/
I have attached a touchstart listener to it, like this:
我已经为它附加了一个 touchstart 监听器，如下所示：
other_options.addEventListener('touchstart', function(e) {
event.preventDefault();
}, false);
What I want to do, and I've already looked through the values of 'e' but I can't find any value consistent enough (values don't seem right to me when I try them) to do what I want.
我想要做什么，并且我已经查看了 'e' 的值，但是我找不到任何足够一致的值（当我尝试它们时，这些值对我来说似乎不正确）来做我想做的事。
I know the size of those rows. I just want to be able to take the Y coordinate of where the touchstart event fired, being 0 the upper coordinate of the element. That way, Math.floor(y / ROW_SIZE) will give me the row the touchstart event was started on.
我知道这些行的大小。我只是希望能够获取触发 touchstart 事件的 Y 坐标，将元素的上坐标设为 0。这样， Math.floor(y / ROW_SIZE) 会给我开始 touchstart 事件的行。
回答by BalaKrishnan?
You have to access like this.
你必须像这样访问。
e.touches[0].clientX/clientY.
the number touchs and touch information can be access via e.touches.
触摸次数和触摸信息可以通过 e.touches 访问。
Take look at this FAQ.
看看这个常见问题。
How to get the x/y coordinates in touch events ?
here is the touch event documentation.
这是触摸事件文档。
By the way, events will return x/y coordinates relative to the window only. we can't changed that. what you can do this. top= 0 - element.top; x= clientx-top.
顺便说一下，事件将仅返回相对于窗口的 x/y 坐标。我们不能改变这一点。你能做什么。top= 0 - element.top; x= clientx-top.
回答by Venkat
It is better to use getBoundingClientRect()method to calculate top & left values of an element.
最好使用getBoundingClientRect()方法来计算元素的顶部和左侧值。
The above approach, element.top, may not give top & left values relative to the viewport if the element is inside another container.
element.top如果元素位于另一个容器内，则上述方法可能不会给出相对于视口的顶部和左侧值。
So to calculate touch co-ordinates relative to the element, we can do as below.
因此，要计算相对于元素的触摸坐标，我们可以执行以下操作。
var rect = element.getBoundingClientRect();
xCoordinate = event.touches[0].clientX - rect.left;
yCoordinate = event.touches[0].clientY - rect.top;
To find out more about getBoundingClientRect()method, click here.
要了解有关getBoundingClientRect()方法的更多信息，请单击此处。
