滚动时更改div的高度

Question

I'm doing a web application using reactjs. And I have a need of changing the height of a div when I'm scrolling down and restore to the original height when I'm scrolling up. I'm not sure if there's a CSS only solution to what I need. What's the way of achieving what i have described above.

class InternalGroupsPage extends Component {
     constructor() {
     super();
}

render() {

return (
         <div className="body_clr">

            <div className="group_page_header">
                    This is the div i want to change the height when scrolling
            </div>

            <div>
                    Other stuff
            </div>
         </div>

        );
    }
}

CSS

.group_page_header {

    width: 100%;
    height: 220px;
    background-color: #0b97c4;
    position: fixed;
    margin-top: 50px;
    z-index: 1;

}

.body_clr {

    overflow-y: scroll;
    width: 100%;
    height: 100%;
    position: fixed;
    background-color: #eceff1;

}

Answer 1

So, basically like I mentioned in the comment.

Basically you need to toggle a state variable + className when the scrollTop passes a certain point for the rerender to happen.

Here's the handle scroll function:

handleScroll(event) {
      var scrollTop = event.srcElement.body.scrollTop;
      var isScrollUp = this.getScrollDirection();

      if(isScrollUp) {
        this.setState({
          hideHeader: true,
        });
      } else {
        this.setState({
          hideHeader: false,
        });
      }
  };

To detect the scroll direction:

getScrollDirection() {
    var currentScrollTop = document.body.scrollTop;
    var isScrollUp = currentScrollTop < this.previousScrollTop;
    this.previousScrollTop = currentScrollTop;
    return isScrollUp;
  }

And the render function to toggle the classes

 render() {
    var headerClassName = this.state.hideHeader ? `group_page_header hideHeader` : `group_page_header showHeader`;
    console.log('classNAme ->', headerClassName)
    return (
      <div className="body_clr">
        <div className={headerClassName}>
        This is the div i want to change the height when scrolling
        </div>
        <div className="other-stuff">
          Other stuff
        </div>
      </div>
    );
  }

Here's the fiddle

You can update your small css changes and try it out. Basically this should be the direction you should be following to attain this requirement.

Answer 2

Using JQuery:

$('.body_clr').scroll( function() {

    var topPos = $(this).scrollTop();

    var calcheight = 0; // use this variable to calculate the height of the div based on topPos

    $('.group_page_header').height( calcheight );

})