安卓弹出键盘隐藏fixed定位相关的元素(obj必须是class)

//安卓弹出键盘隐藏fixed定位相关的元素(obj必须是class)
function displayFixed(obj){
var h = document.body.scrollHeight;
window.onresize = function(){
if (document.body.scrollHeight < h) {
document.getElementsByClassName(obj)[0].style.display = "none";
}else{
document.getElementsByClassName(obj)[0].style.display = "block";
}
};
}