`pointermove` event not working with touch. Why not?

问题

I have this pen:

https://codepen.io/anon/pen/eyKeqK

If you try it on a touch-screen device (f.e. visit the pen on your phone) you'll notice that when you drag, the white light (the little sphere) only moves for a tiny bit then it stops working.

The logic for the movement is in the pointermove event handler. It works fine on Desktop using a mouse, just not with touch.

How do we fix this so the light keeps moving while touch dragging (not just for a moment), and as bonus how do we prevent it from refreshing the page when we pull down?

Here's the code for the pen:

HTML (Slim):

/! Made with http://github.com/trusktr/infamous

script src="https://cdn.rawgit.com/trusktr/e37dbc24c51b9d3e2f9e508e75cf8f99/raw/2a3fee4ee506a05cc4ac509f592f0c3af1ddfed4/infamous-mixed-mode-3.js"
script src="https://unpkg.com/tween.js@16.6.0/src/Tween.js"

i-scene experimental-webgl="true" id="scene" TODO-perspective="800" backgroundColor="0 0 0" backgroundOpacity="0" style="perspective: 800px" shadowmap-type="pcfsoft"

    i-ambient-light color="#404040" intensity="1"

    i-dom-plane id="bg" sizeMode="proportional proportional" size="1 1 0"

        i-node id="button-container" position="0 0 6" size="600 31 0" align="0.5 0.5 0" mountPoint="0.5 0.5 0"

            - for n in (0..4)
                i-dom-plane sizeMode="literal proportional" size="100 1 0" align="#{n*0.25} 0 0" mountPoint="#{n*0.25} 0 0"
                    button button #{n+1}

        i-point-light id="light" color="white" position="300 300 120" size="0 0 0" cast-shadow="true" intensity="1"
            i-mesh has="sphere-geometry basic-material" size="10 10 10" color="white" receive-shadow="false" cast-shadow="false" style="pointer-events: none"

CSS (Stylus):

body, html
    width 100%
    height 100%
    margin 0
    padding 0
    font-family sans-serif

i-node
    text-align center

#bg
    background #62B997

button
    width 100%
    height 100%
    white-space nowrap
    border-radius 0px
    border 1px solid #534334
    background lighten(#FB752C, 20%)
    color darken(#534334, 10%)
    outline none // remove those darn ugly browser-specific outlines
    &:focus, &:hover
        background #FB752C
        color darken(#534334, 20%)

JavaScript:

infamous.html.useDefaultNames()
const Motor = infamous.core.Motor

light.threeObject3d.shadow.radius = 3
light.threeObject3d.distance = 20000
light.threeObject3d.shadow.bias = 0.00001

document.addEventListener('pointermove', e => {
    e.preventDefault()
    light.position.x = e.clientX
    light.position.y = e.clientY
})

let downTween, upTween, pressedButton

// On mouse down animate the button downward
document.addEventListener('pointerdown', e => {
    if ( is( e.target, 'button' ) ) {

        pressedButton = e.target

        if (upTween) {
            upTween.stop()
            upTween = null
        }

        downTween = new TWEEN.Tween(e.target.parentNode.position)
            .to({z: -6}, 75)
            .start()
            .onComplete(() => downTween = null)

        Motor.addRenderTask(time => {
            if (!downTween) return false
            downTween.update(time)
        })

    }
})

// On mouse up animate the button upward
document.addEventListener('pointerup', e => {
    if ( pressedButton ) {

        if (downTween) {
            downTween.stop()
            downTween = null
        }

        upTween = new TWEEN.Tween(pressedButton.parentNode.position)
            .to({z: 0}, 75)
            .start()
            .onComplete(() => upTween = null)

        Motor.addRenderTask(time => {
            if (!upTween) return false
            upTween.update(time)
        })

    }
})

// The following is a temporary hack because opacity isn't
// exposed through the HTML API yet. work-in-progress...
setTimeout(() => {
    Array.from( document.querySelectorAll('i-dom-plane') ).forEach(n => {
        n.threeObject3d.material.opacity = 0.3
    })

    scene._needsToBeRendered()
}, 0)

function is( el, selector ) {
    if ( [].includes.call( document.querySelectorAll( selector ), el ) ) return true
    return false
}

回答1:

On the MDN documentation page about pointermove, there's this line:

The pointermove event is fired when a pointer changes coordinates, and the pointer has not been canceled by a browser touch-action.

_{source, emphasis mine}

After a short period of time, the (mobile) browser will claim the pointermove event for "native" behavior like panning the page.

The designed, simple solution is to use the css property touch-action and set it to none on the container that has the event handler.

Here's the css property added to your codepen: https://codepen.io/anon/pen/XVBMvL

Or in a simplified example:

• Set your browser to emulate touch (in Chrome, dev. tools > Sensors > Touch)
• Start an interaction in the left part, and the dot will follow your finger
• Start an interaction in the right part, and you'll notice it will quickly fail like in the provided example

var dot = document.querySelector(".dot")
document.body.addEventListener("pointermove", function(ev) {
  dot.style.transform = `translate3d(${ev.clientX}px, ${ev.clientY}px, 0)`;

}, false);

* { margin: 0; padding: 0 }

.wrapper { 
  display: flex; 
  height: 100vh;
}

.hasTouchAction, 
.noTouchAction {
  flex-grow: 1;
  text-align: center;
  background: #efefef;
}

.hasTouchAction {
  touch-action: none;
}

.noTouchAction {
  background: #ccc;
}

.dot {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: red;
  position: absolute;
  top: -8px;
  left: -8px;
}

<div class="wrapper">
  <div class="hasTouchAction">
    With <code>touch-action: none</code>
  </div>

  <div class="noTouchAction">
    Without <code>touch-action</code>
  </div>
</div>

<div class="dot"></div>

Make sure you don't break important things and hurt accessibility. Also spend some time to investigate browser support. This worked for me with touch emulated events in Chrome, but might not work in every browser...

来源：https://stackoverflow.com/questions/48124372/pointermove-event-not-working-with-touch-why-not