<div class="ys-float-btn" 
    :style="{'width': itemWidth+'px','height': itemHeight+'px','left': left+'px','top': top+'px'}"    
    ref="div"    
    @touchstart.prevent="(e) => {dragStart(e)}"     
    @touchend.prevent="(e) => {dragEnd(e)}"     
    @touchmove.prevent="(e) => {dragProgress(e)}"    
    >    
    <img src="./../assets/fc-icon.png" />
</div>

// 代码直接在 vue 项目里，可自行改为js/jquery 写法
data () {
    return {
        gapWidth: 10,
        itemWidth: 20, // 图标的宽度
        itemHeight: 30 // 图标的高度
    }
},
created() {      
    this.clientWidth = document.documentElement.clientWidth;     
    this.clientHeight = document.documentElement.clientHeight;      
    this.left = this.clientWidth - this.itemWidth - this.gapWidth;      
    this.top = this.clientHeight*0.8;   }
 
methods: {    
    dragStart(e) {        
        this.$refs.div.style.transition = 'none';
    },
    dragEnd(e) {        
        this.$refs.div.style.transition = 'all 0.3s';        
        if (this.left > this.clientWidth/2) {          
            this.left = this.clientWidth - this.itemWidth - this.gapWidth;
        } else {          
            this.left = this.gapWidth;        
        }      
    },      
    dragProgress(e) {        
        if (e.targetTouches.length === 1) {          
            let touch = event.targetTouches[0];          
            this.left = touch.clientX - this.itemWidth/2;              
            this.top = touch.clientY - this.itemHeight/2;        
        }      
    }
}