Question

使用指针事件，我找不到合适的事件来触发智能手机上的基于手指的触摸（已通过Chrome浏览器Android和具有移动仿真功能的Chrome Devtools进行了测试）。

我需要什么：如果您触摸动作通过并同时按住手指在屏幕上移动，则会发生“悬停”事件。

也就是说，将手指放到元素外部，直到完全穿过元素之后才向上移动手指。

我附上了一段经过简化的代码：我不需要蓝色元素的事件，只需要片段中红色元素的相应“输入/输出”事件即可。该示例JS代码将为鼠标触发，但在移动设备上不会触发任何console.infos。

var elem = document.querySelector(".element");

elem.addEventListener("pointerover", function() {
    console.clear();
    console.info("pointerover triggered");
});
elem.addEventListener("pointerenter", function() {
    console.clear();
    console.info("pointerenter triggered");
});
elem.addEventListener("pointerleave", function() {
    console.clear();
    console.info("pointerleave triggered");
});

.outer {
    width: 100px;
    height: 100px;
    border: 3px solid grey;
    font-size: 12px;
    color: white;
    text-align:center;
    touch-action: none;
    
}

.start {
   position: relative;
   top:0px;
   left:0px;
   width: 100px;
   height: 20px;
   background-color: blue;
}

.element {
   position: relative;
   top: 20px;
   left: 0px;
   width: 100px;
   height: 20px;
   background-color: red;
}

.end {
   position: relative;
   top: 40px;
   right: 0;
   width: 100px;
   height: 20px;
   background-color: blue;
}

<div class="outer">
    <div class="start">Start touch here</div>
    <div class="element">Move over here</div>
    <div class="end">End touch here</div>
</div>

Answer 1

我希望我能正确理解你。我为您编写并测试了两种不同的解决方案：指针事件和触摸事件。在此事件的每个移动事件中，您可以使用功能 document.elementFromPoint() 检测当前元素。

具有指针事件的解决方案

也许您可以使用指针事件–它们可以在具有移动设备仿真功能的Chrome Devtools中使用，但不能在我的Android设备（我认为我的设备太旧）上使用。或者，您可以将其与Pointer Events Polyfill一起使用。您可以查看 here 的指针事件的浏览器兼容性。

var elementFromPoint,
    isFingerDown = false,
    isThroughElemMoved = false,
    elem = document.querySelector('.element'),
    output = document.querySelector('#output');

document.addEventListener('pointerdown', function(e)
{
    if(elem != e.target)
    {
        isFingerDown = true;
        output.innerHTML = 'pointer-START';
    }
});

document.addEventListener('pointermove', function(e)
{
    elementFromPoint = document.elementFromPoint(e.pageX - window.pageXOffset, e.pageY - window.pageYOffset);

    if(elem == elementFromPoint)
    {
        isThroughElemMoved = true;
        output.innerHTML = 'pointer-MOVE';
    }
});

document.addEventListener('pointerup', function(e)
{
    if(isFingerDown && isThroughElemMoved && elem != elementFromPoint)
        output.innerHTML = 'It is done!';

    isFingerDown = isThroughElemMoved = false;
});

.outer
{
    width: 100px;
    height: 100px;
    border: 3px solid grey;
    font-size: 12px;
    color: white;
    text-align: center;
    /*touch-action: none*/
}
.outer div{position: relative; left: 0; height: 20px}
.start{top: 0; background: blue}
.element{top: 20px; background: red}
.end{top: 40px; background: blue}

<div class="outer">
    <div class="start">Start touch here</div>
    <div class="element">Move over here</div>
    <div class="end">End touch here</div>
</div>
<br><br>
<div id="output">info</div>

触摸事件解决方案

但是您也可以使用 touch events 。不幸的是，事件touchenter和touchleave已从规范中删除，由于这些事件，我们也必须使用document.elementFromPoint()编写变通办法。

以下代码段仅在移动设备仿真（通过Chrome Devtools测试）或支持触摸事件的设备（通过Android测试）上有效。

var elementFromPoint,
    isFingerDown = false,
    isThroughElemMoved = false,
    elem = document.querySelector('.element'),
    output = document.querySelector('#output');

document.addEventListener('touchstart', function(e)
{
    if(elem != e.target)
    {
        isFingerDown = true;
        output.innerHTML = 'touch-START';
    }
});

document.addEventListener('touchmove', function(e)
{
    var touch = e.touches[0];
    
    elementFromPoint = document.elementFromPoint(touch.pageX - window.pageXOffset, touch.pageY - window.pageYOffset);

    if(elem == elementFromPoint)
    {
        isThroughElemMoved = true;
        output.innerHTML = 'touch-MOVE';
    }
});

document.addEventListener('touchend', function(e)
{
    if(isFingerDown && isThroughElemMoved && elem != elementFromPoint)
        output.innerHTML = 'It is done!';

    isFingerDown = isThroughElemMoved = false;
});

.outer
{
    width: 100px;
    height: 100px;
    border: 3px solid grey;
    font-size: 12px;
    color: white;
    text-align: center;
    /*touch-action: none*/
}
.outer div{position: relative; left: 0; height: 20px}
.start{top: 0; background: blue}
.element{top: 20px; background: red}
.end{top: 40px; background: blue}

<div class="outer">
    <div class="start">Start touch here</div>
    <div class="element">Move over here</div>
    <div class="end">End touch here</div>
</div>
<br><br>
<div id="output">info</div>

也许以下链接可以为您提供帮助：

Answer 2

尝试一下

<script>
    var startElem = document.querySelector(".start");
    var endElem = document.querySelector(".end");
    var elem = document.querySelector(".element");

    var started = false;
    var passedThroughStart = false;
    var passedThroughEnd = false;
    var ended = false;

    startElem.addEventListener("pointerdown", function(e){
        started = true;
    });

    window.addEventListener("pointermove", function(e) {
        var x = e.clientX;
        var y = e.clientY;
        var bounds = elem.getBoundingClientRect();

        if( !passedThroughStart &&
            x > bounds.left && x < bounds.left + bounds.width &&
            y > bounds.top && y < bounds.top + bounds.height
        ){
            passedThroughStart = true;
        }

        if( passedThroughStart && !passedThroughEnd &&
            x > bounds.left && x < bounds.left + bounds.width &&
            y > bounds.top + bounds.height
        ){
            passedThroughEnd = true;
        }
    })

    window.addEventListener("pointerup", function(e) {
        var x = e.clientX;
        var y = e.clientY;
        var bounds = endElem.getBoundingClientRect();

        ended = ( x > bounds.left && x < bounds.left + bounds.width && y > bounds.top && y < bounds.top + bounds.height)

        if( started && passedThroughStart && passedThroughEnd && ended ){
            console.log("Hooray!");
        }

        started = false;
        passedThroughStart = false;
        passedThroughEnd = false;
        ended = false;
    });
</script>

或者使用pointerenter和pointerleave而不是pointermove

elem.addEventListener('pointenter', function(e) {
    passedThroughStart = true;
}
elem.addEventListener('pointleave', function(e) {
    passedThroughEnd = true;
}

PointerEvents：检测“通过”元素的触摸

2 个答案: