移动端下拉刷新原理

<!DOCTYPE html>

<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>dropDownRefresh</title>
    <style type="text/css">
        html,body,p,ul,li {
            margin: 0;
            padding: 0;
        }
        #refreshContainer li {
            background-color: #eee;
            margin-bottom: 1px;
            padding: 20px 10px;
        }
        .refreshText {
            position: absolute;
            width: 100%;
            line-height: 50px;
            text-align: center;
            left: 0;
            top: 0;
            transform: translateY(-50px);
        }
    </style>
</head>
<body>
    <div class="parent">
        <p class="refreshText"></p>
        <ul id="refreshContainer">
            <li>111</li>
            <li>222</li>
            <li>333</li>
            <li>444</li>
            <li>555</li>
            <li>666</li>
            <li>777</li>
            <li>888</li>
            <li>999</li>
            <li>000</li>
            <li>001</li>
            <li>002</li>
            <li>003</li>
            <li>004</li>
            <li>005</li>
        </ul>
    </div>
    <script type="text/javascript">
        window.onload = function(){
            //1.获取到列表的dom，刷新显示部分的dom，列表父容器的dom
            let container = document.querySelector('#refreshContainer');
            let refreshText = document.querySelector('.refreshText');
            let parent = document.querySelector('.parent');
            //2.定义一些需要常用的变量
            let startY = 0;//手指触摸最开始的Y坐标
            //3.给列表dom监听touchstart事件,得到起始位置的Y坐标
            parent.addEventListener('touchstart',function(e){
                startY = e.touches[0].pageY;
            });
            //4.给列表dom监听touchmove事件，当移动到一定程度需要显示上面的文字
            parent.addEventListener('touchmove',function (e) { 
                if(isTop() && (e.touches[0].pageY-startY) > 0){
                    console.log('下拉了');
                    refreshText.style.height = "50px";
                    parent.style.transform = "translateY(50px)";
                    parent.style.transition = "all ease 0.5s";
                    refreshText.innerHTML = "释放立即刷新...";
                }
            });
            //5.给列表dom监听touchend事件，此时说明用户已经松开了手指，应该进行异步操作了
            parent.addEventListener('touchend',function (e) { 
                if(isTop()){
                    refreshText.innerHTML = "正在刷新...";
                    setTimeout(function(){
                        parent.style.transform = "translateY(0)";
                        console.log('成功刷新');
                    },2000)
                }
                return;
            })
            function isTop(){
				//判断是否有滚动条
                var t = document.documentElement.scrollTop||document.body.scrollTop;
                return t === 0 ? true : false;
            }
        }
    </script>
</body>
</html>
移动端下拉刷新原理

猜你喜欢
