具有固定位置的平滑滚动标题

Question

当我将位置更改为固定时如何创建平滑滚动。我尝试添加动画，但它不起作用。更好地使用 jquery animation();

$(window).scroll(function() {
  var sticky = $('.mobile-menu'),
    scroll = $(window).scrollTop();

  if (scroll >= 40) sticky.addClass('fixed');
  else sticky.removeClass('fixed');
});

header {
  padding: 20px 40px;
  background: gray;
  width: 100%;
  -webkit-transition: position 10s;
  -moz-transition: position 10s;
  -ms-transition: position 10s;
  -o-transition: position 10s;
  transition: position 10s;
}
section {
  height: 150vh;
}
.fixed {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<header class="mobile-menu">Text here</header>
<section>Sugar plum muffin cookie pastry oat cake icing candy canes chocolate. Gummi bears chupa chups fruitcake dessert jelly. Muffin cookie ice cream soufflé pastry lollipop gingerbread sweet. Unerdwear.com bonbon candy marzipan bonbon gummies chocolate cake
  gummi bears powder. Unerdwear.com tart halvah chocolate cake dragée liquorice. Sugar plum chocolate bar pastry liquorice dragée jelly powder. Jelly tootsie roll applicake caramels. Marzipan candy tootsie roll donut. Gummies ice cream macaroon applicake.</section>

Answer 1

您可以使用@keyframes为滚动添加一些过渡效果。

$(window).scroll(function() {
  var sticky = $('.mobile-menu'),
    scroll = $(window).scrollTop();
   
  if (scroll >= 40) { 
    sticky.addClass('fixed'); }
  else { 
   sticky.removeClass('fixed');

}
});

header {
  padding: 20px 40px;
  background: gray;
  width: 100%;
  
  -webkit-transition: all 0.5s ease;
  -moz-transition: position 10s;
  -ms-transition: position 10s;
  -o-transition: position 10s;
  transition: all 0.5s ease;
}
section {
  height: 150vh;
}


.fixed {
  position: fixed;
  top: 0;
  left: 0;
  animation: smoothScroll 1s forwards;
}
@keyframes smoothScroll {
	0% {
		transform: translateY(-40px);
	}
	100% {
		transform: translateY(0px);
	}
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<header class="mobile-menu">Text here</header>
<section>Sugar plum muffin cookie pastry oat cake icing candy canes chocolate. Gummi bears chupa chups fruitcake dessert jelly. Muffin cookie ice cream soufflé pastry lollipop gingerbread sweet. Unerdwear.com bonbon candy marzipan bonbon gummies chocolate cake
  gummi bears powder. Unerdwear.com tart halvah chocolate cake dragée liquorice. Sugar plum chocolate bar pastry liquorice dragée jelly powder. Jelly tootsie roll applicake caramels. Marzipan candy tootsie roll donut. Gummies ice cream macaroon applicake.</section>

Answer 2

根据评论编辑。

如果在滚动时将position 更改为fixed，则会产生不希望的跳转行为。

最好的办法是防止滚动时定位，在40px 之后设置fixed 或从一开始就几乎相同，所以我建议你在你的jQuery 上删除这部分，并让你的@987654325 @fixed从头开始：

//if (scroll >= 40) sticky.addClass('fixed');
//else sticky.removeClass('fixed');

以下片段：

$(window).scroll(function() {
  var sticky = $('.mobile-menu'),
    scroll = $(window).scrollTop();
});

body {
  position: relative;
}
header {
  padding: 20px 40px;
  background: gray;
  width: 100%;
  -webkit-transition: position 10s;
  -moz-transition: position 10s;
  -ms-transition: position 10s;
  -o-transition: position 10s;
  transition: position 10s;
}
section {
  height: 150vh;
  position: relative;
  top: 60px;
}
.fixed {
  position: fixed;
  z-index: 1;
  top: 0;
  left: 0;
  right: 0;
  width: 100%;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<header class="mobile-menu fixed">Text here</header>
<section>Sugar plum muffin cookie pastry oat cake icing candy canes chocolate. Gummi bears chupa chups fruitcake dessert jelly. Muffin cookie ice cream soufflé pastry lollipop gingerbread sweet. Unerdwear.com bonbon candy marzipan bonbon gummies chocolate cake
  gummi bears powder. Unerdwear.com tart halvah chocolate cake dragée liquorice. Sugar plum chocolate bar pastry liquorice dragée jelly powder. Jelly tootsie roll applicake caramels. Marzipan candy tootsie roll donut. Gummies ice cream macaroon applicake.</section>