h5仿转转banner轮播效果

h5实现banner图与背景图同时切换的效果（swiper插件）

1、要在.swiper-box的div外面加一个div#big-bg，设置样式position：absolute；

2、css样式中写好3个背景图样式：.banner-bg1、.banner-bg2、.banner-bg3

3、需要查看项目工程里swiper.js的源代码(node_modules/swiper/dist/js/swiper.js)，找到控制自动轮播和触屏滑动的事件中emit出的方法名：autoplay、touchMove

 

4、在需要用到swiper插件的组件的初始化swiper的方法里，加入该方法的回调函数

_.initSwiper(){
    var mySwiper = new Swiper(".swiper-box",{
        ....
      
    on:{
    beforeSlideChangeStart:function(){
        if(this.activeIndex == 0){
        this.$('#big-bg').addClass("banner-bg1");
        }
    },
    touchMove:function(){
        let that = this;
        setTimeout(function() {      //因为touchMove触发后，activeIndex更新延后了，所以延迟10ms再判断activeMove值
        if(that.activeIndex == 0){
            that.$('#big-bg').removeClass("banner-bg2");
            that.$('#big-bg').removeClass("banner-bg3");
            that.$('#big-bg').addClass("banner-bg1");
        }else if(that.activeIndex == 1){
            that.$('#big-bg').removeClass("banner-bg1");
            that.$('#big-bg').removeClass("banner-bg3");
            that.$('#big-bg').addClass("banner-bg2");
        }else if(that.activeIndex == 2){
            that.$('#big-bg').removeClass("banner-bg1");
            that.$('#big-bg').removeClass("banner-bg2");
            that.$('#big-bg').addClass("banner-bg3");
        }else{
            that.$('#big-bg').removeClass("banner-bg1");
            that.$('#big-bg').removeClass("banner-bg3");
            that.$('#big-bg').addClass("banner-bg2");
        }
        }, 10);
    },
    autoplay:function(){
        if(this.activeIndex == 0){
            this.$('#big-bg').removeClass("banner-bg2");
            this.$('#big-bg').removeClass("banner-bg3");
            this.$('#big-bg').addClass("banner-bg1");
        }else if(this.activeIndex == 1){
            this.$('#big-bg').removeClass("banner-bg1");
            this.$('#big-bg').removeClass("banner-bg3");
            this.$('#big-bg').addClass("banner-bg2");
        }else if(this.activeIndex == 2){
            this.$('#big-bg').removeClass("banner-bg1");
            this.$('#big-bg').removeClass("banner-bg2");
            this.$('#big-bg').addClass("banner-bg3");
        }else{
            this.$('#big-bg').removeClass("banner-bg1");
            this.$('#big-bg').removeClass("banner-bg3");
            this.$('#big-bg').addClass("banner-bg2");
        }
    },    
}