动画滚动容器从点A到点B的左

问题描述

我有一个可滚动的容器，它的scrollLeft在每个requestAnimationFrame刻度(读取间隔)上从currentValue变为currentValue + 10.

I have a scrollable container whose scrollLeft changes from the currentValue to currentValue + 10 on each requestAnimationFrame tick (read interval).

但是，此过渡会产生交错效果，导致立即发生滚动，而不是从currentValue动画到currentValue + 10.就像我们对过渡所做的那样，有没有办法在这种情况下定义缓动函数?

However, this transition produces a staggered effect leading to the scrolling happening in an instant instead of animating from currentValue to currentValue + 10. Is there a way to define an easing function in this case just like we do for transitions?

此外，我需要在没有jQuery的情况下进行操作.

Also, I need to do this without jQuery.

推荐答案

可以，但是您需要知道动画进行到多远的百分比.这是一种简单的动画方法，它可以接收带有回调和动画持续时间(以秒为单位)的对象.

Sure you can, but you need to know the percentage of how far the animation has gone. Here is a simple method for animations that takes in an object with callbacks and animation duration in seconds.

/**
* @param callbackObj Object An object with callbacks in .start, .progress, and .done
* @param duration Integer Total duration in seconds
*/
function animate(callbackObj, duration) {
        var requestAnimationFrame = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame;
        var startTime = 0, percentage = 0, animationTime = 0;

        duration = duration*1000 || 1000;

        var animation = function(timestamp) {

          if (startTime === 0) {
              startTime = timestamp;
            } else {
              animationTime = timestamp - startTime;
            }

          if (typeof callbackObj.start === 'function' && startTime === timestamp) {
             callbackObj.start();

             requestAnimationFrame(animation);
          } else if (animationTime < duration) {
             if (typeof callbackObj.progress === 'function') {
               percentage = animationTime / duration;
               callbackObj.progress(percentage);
             }

            requestAnimationFrame(animation);
          } else if (typeof callbackObj.done === 'function'){
              callbackObj.done();
          }
        };

      return requestAnimationFrame(animation);
}

然后将这种方法与Robert Penner的缓动功能结合起来: https://gist.github.com/gre/1650294

You then combine this method with Robert Penner's Easing Functions: https://gist.github.com/gre/1650294

function easeInOutQuad(t) { return t<.5 ? 2*t*t : -1+(4-2*t)*t },

最终方法可能如下所示:

And a final method could look something like this:

function sideScroll(rangeInPixels) {
  var element = document.getElementById('scrollableContainer');

  if (element) {
    var sequenceObj = {};
    var seconds = 0.3;
    var startingScrollPosition = element.scrollY;

    sequenceObj.progress = (function(percentage) {
      element.scroll( (startingScrollPosition + easeInOutQuad(percentage))*rangeInPixels) , 0);
    }

    animate(sequenceObj, seconds);
  }
}

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