jQuery live scroll event on mobile (work around)

问题:

The age old problem: Getting the scroll event to fire while a user is scrolling on an element while on a mobile site or app(web view).

All I'm looking for is access to the correct scrollTop() value while a user is scrolling my page on a mobile device instead of getting it when the user stops.

I'm sure there is a workaround somewhere, if I'm correct this limitation is set by iOS and there has been discussion over it for the past few years.

I've tried implementing native scroll emulators but none of them seem to be working how I want and to be honest it seems like overkill if all I really want is a persistent scrollTop() while a user is scrolling.

I'm currently thinking about maybe starting a counter on touchStart and stopping it on touchStop but something tells me I'm wasting my time.

Any help guys?

回答1:

With jQuery:

$('body').bind('touchmove', function(e) { 
    console.log($(this).scrollTop()); // Replace this with your code.
});

This should give you a consistent stream of the scrollTop value when the user scrolls, but be careful as it's going to fire even while the user is just holding his finger on the screen.

Note that if you're using jQuery >= 1.7 the preferred binding method is .on() instead of the .bind() method I've used in my example. In that case my example would be

$('body').on({
    'touchmove': function(e) { 
        console.log($(this).scrollTop()); // Replace this with your code.
    }
});

Source: https://github.com/dantipa/pull-to-refresh-js/blob/master/jquery.plugin.pullToRefresh.js

回答2:

maybe you could take a look at how iScroll does it in their _move-method which is bound to the touchmove event: https://github.com/cubiq/iscroll/blob/master/src/core.js#L152

It's a bit complicated but i'm sure you'll figure it out. You could also just use iScroll to begin with and bind to their scrollmove event (I'm not sure how it's called on iScroll 5 but it was onScrollMove in iScroll 4). that.y will then give you the correct value.

回答3:

I had to go the iScroll route to do this. I wrote up my implementation here: https://stackoverflow.com/a/23140322/229315