H5觸摸事宜推斷滑動方向

為了給觸摸界面供應有力支撐, 觸摸事宜供應了相應用戶對觸摸屏或許觸摸板上操縱的才能.

接口

TouchEvent

TouchEvent 是一類形貌手指在觸摸平面(觸摸屏、觸摸板等)的狀況變化的事宜。這類事宜用於形貌一個或多個觸點,使開發者能夠檢測觸點的挪動,觸點的增添和削減,等等。每 個 Touch 對象代表一個觸點; 每一個觸點都由其位置,大小,外形,壓力大小,和目的 element 形貌。 TouchList 對象代表多個觸點的一個列表.

觸摸事宜的範例

為了區分觸摸相干的狀況轉變,存在多種範例的觸摸事宜。能夠經由過程搜檢觸摸事宜的 TouchEvent.type 屬性來肯定當前事宜屬於哪一種範例

  • touchstart:當用戶在觸摸平面上安排了一個觸點時觸發。
  • touchend:當一個觸點被用戶從觸摸平面上移除(當用戶將一個手指脫離觸摸平面)時觸發。
  • touchmove:當用戶在觸摸平面上挪動觸點時觸發。
  • touchcancel:當觸點因為某些原因被中綴時觸發。

推斷滑動方向

基本原理就是紀錄最先滑動(touchStart)和完畢滑動(touchEnd)的坐標位置,然後舉行相對位置的盤算。

touchStart:function(e){
    startX = e.touches[0].pageX;
    startY = e.touches[0].pageY;
    e = e || window.event;
 },
touchEnd:function(e){
    const that = this;
    endX = e.changedTouches[0].pageX;
    endY = e.changedTouches[0].pageY;
    that.upOrDown(startX,startY,endX,endY);
},
upOrDown:function (startX, startY, endX, endY) {
    const that = this;
    let direction = that.GetSlideDirection(startX, startY, endX, endY);
    switch(direction) {
      case 0:
        console.log("沒滑動");
        break;
      case 1:
        console.log("向上");
        break;
      case 2:
        console.log("向下");
        break;
      case 3:
        console.log("向左");
        break;
      case 4:
        console.log("向右");
        break;
      default:
        break;
    }
  },
//依據出發點和盡頭返回方向 1:向上,2:向下,3:向左,4:向右,0:未滑動
  GetSlideDirection:function (startX, startY, endX, endY) {
    const that = this;
    let dy = startY - endY;
    let dx = endX - startX;
    let result = 0;
    //假如滑動間隔太短
    if(Math.abs(dx) < 2 && Math.abs(dy) < 2) {
      return result;
    }
    let angle = that.GetSlideAngle(dx, dy);
    if(angle >= -45 && angle < 45) {
      result = 4;
    }else if (angle >= 45 && angle < 135) {
      result = 1;
    }else if (angle >= -135 && angle < -45) {
      result = 2;
    }
    else if ((angle >= 135 && angle <= 180) || (angle >= -180 && angle < -135)) {
      result = 3;
    }
    return result;
  },
  //返回角度
  GetSlideAngle:function (dx, dy) {
    return Math.atan2(dy, dx) * 180 / Math.PI;
  }

原生JS要領

除了H5新增的要領外,還能夠用原生JS推斷view的滑動方向,代碼以下(可直接運轉):
要注意的是chrome對document.body.scrollTop一直是0,須要改成document.documentElement.scrollTop

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>菜鳥教程(runoob.com)</title>
  <style>
    div {
      border: 1px solid black;
      width: 200px;
      height: 100px;
      overflow: scroll;
    }
  </style>
</head>
<body style="overflow: scroll">
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<h1>HEllo word</h1>
<script>
  function scroll( fn ) {
    var beforeScrollTop = document.documentElement.scrollTop,
      fn = fn || function() {};
    console.log('beforeScrollTop',beforeScrollTop);
    window.addEventListener("scroll", function() {
      var afterScrollTop = document.documentElement.scrollTop,
        delta = afterScrollTop - beforeScrollTop;
      console.log('beforeScrollTop',beforeScrollTop);
      console.log('afterScrollTop',afterScrollTop);
      if( delta === 0 ) return false;
      fn( delta > 0 ? "down" : "up" );
      beforeScrollTop = afterScrollTop;
    }, false);
  }

  scroll(function(direction) { console.log(direction) });
</script>

</body>
</html>
    原文作者:aishuishui2066
    原文地址: https://segmentfault.com/a/1190000015171176
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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