安卓input框获取焦点时，底部按钮会顶上去的解决方法

var h = document.body.scrollHeight;
window.onresize = function(){
    if (document.body.scrollHeight < h) {
        document.getElementById("saveBtn").style.display = "none";
    }else{
        document.getElementById("saveBtn").style.display = "block";
    }
};