感谢 funkybro 的评论，但不幸的是，在文档级别拦截触摸事件时，我仍然可以观察到相同的错误行为。这是正在发生的事情的痕迹：
finger 1 touches elem1:
20:44:00.130 onTouchStart:
touches len=1 (elem1)
changedTouches len=1 (elem1)
finger 2 touches elem2 (finger 1 still presses elem1 and has not been released):
20:44:01.066 onTouchStart:
touches len=2 (elem1,elem2)
changedTouches len=1 (elem2)
finger 2 being released (finger 1 still presses elem1 and has not been released):
this is where things begin to go wrong: we receive two touchend events consecutively for
both elem1 and elem2,even though finger 1 is still holding on elem1 and has never released it.
Also the event.touches array is empty for both events, which is wrong since elem1 is still
being pressed.
20:44:08.241 onTouchEnd: touches len=0
changedTouches len=1 (elem1)
20:44:08.251 onTouchEnd: touches len=0
changedTouches len=1 (elem2)
after 4 seconds in the same position (finger 1 pressed on elem1, finger 2 released),
we receive a new touchstart event, as if the system wanted to undo the previous mistake
and put things back into a consistent state.
20:44:12.511 onTouchStart:
touches len=1 (elem1)
changedTouches len=1 (elem1)
now releasing finger 1 from elem1, we receive the touchend event
20:44:14.751 onTouchEnd:
touches len=0
changedTouches len=1 (elem1)
编辑：
这是一个代码示例，可在 Safari Mobile 或您自己的设备（不是模拟器）上的 UIWebView 中运行。
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Multi-touch test</title>
<style type="text/css">
div.square {
position:absolute;
width:80px;
height:80px;
opacity:0.5;
}
div#elem1 {
left:50px;
top:50px;
background-color:red;
}
div#elem2 {
left:200px;
top:50px;
background-color:green;
}
textarea#logger {
position:absolute;
width100%;
height:70%;
top:30%;
background-color:grey;
color:white;
overflow: scroll;
}
</style>
<script type="text/javascript">
function log(text) {
logger.value = logger.value + text;
logger.scrollTop = logger.scrollHeight;
}
function touchesDumpStr(touches,logPrefix) {
var str = logPrefix + ', count=' + touches.length + ':';
for (var i=0; i<touches.length; ++i) {
if (typeof touches[i].target.customName != 'undefined') {
str += touches[i].target.customName +' ';
}
}
str += '\n';
return str;
}
function onTouchStart(e) {
log('onTouchStart\n');
log(touchesDumpStr(e.touches, 'touches'));
log(touchesDumpStr(e.targetTouches, 'targetTouches'));
log(touchesDumpStr(e.changedTouches, 'changedTouches'));
for (var i=0; i<e.changedTouches.length; ++i) {
e.changedTouches[i].target.style.opacity=1.0;
}
e.preventDefault();
}
function onTouchEnd(e) {
log('onTouchEnd\n');
log(touchesDumpStr(e.touches, 'touches'));
log(touchesDumpStr(e.targetTouches, 'targetTouches'));
log(touchesDumpStr(e.changedTouches, 'changedTouches'));
for (var i=0; i<e.changedTouches.length; ++i) {
e.changedTouches[i].target.style.opacity=0.5;
}
e.preventDefault();
}
var logger;
function init() {
logger = document.getElementById('logger');
document.getElementById('elem1').customName='elem1';
document.getElementById('elem2').customName='elem2';
document.addEventListener("touchstart", onTouchStart, false);
document.addEventListener("touchend", onTouchEnd, false);
}
</script>
</head>
<body onload="init();">
<div class="square" id="elem1"></div>
<div class="square" id="elem2"></div>
<textarea id="logger" rows="10" cols="45" readonly></textarea>
</body>
</html>