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>