当底部按钮为absolute或者fixed时，安卓下弹起键盘时，按钮也会被弹起

解决方案：window下监听尺寸变化，当小于原始高度时，则button消失

js
created(){
    let initHeight=document.documentElement.clientHeight
    this.buttonShowFn=this.buttonShowFn.bind(this,initHeight)
    window.addEventListener('resize', this.buttonShowFn)
},
destroyed(){
    window.removeEventListener('resize',this.buttonShowFn)
},
methods: {
    buttonShowFn(initHeight){
    this.buttonShow=(initHeight===document.documentElement.clientHeight)
    }
}