完美解决移动端手机熄屏、黑屏计时器停止计算问题

因为浏览器安全机制问题，手机黑屏后，后台运行浏览器停止运行计时器，

这里使用的是H5的一个PageVisibility API（visibilitychange），熄屏时，开始计算黑屏时间，重启时，再次计算；

另一个思路是也可使用iframe引入另一个页面代码使用全局变量进行计算时间，文本暂不深入；

废话不多说，直接上代码：

 

var timer=null;
 function getCode(t){
	var time=29;
	var that= $(t);
	timer=setInterval(function(){
		if(time<=0){
			that.val("");
			that.val("重新发送");
			that.attr("disabled",false);
			that.removeClass('code_style');
			clearInterval(timer);
			that.attr("time",0);
		}else {
			that.attr("disabled",true);
			that.val("");
			that.val("剩余"+(time)+"秒");
			that.attr("time",time);
			time--;
			that.addClass('code_style');
		}
	},1000);
	var cede_times = 0;
    var b=0;
    document.addEventListener("visibilitychange",function()
    {
        if(document.visibilityState=="hidden") {

            b=new Date().getTime();
            cede_times=$("#subCode").attr("time");
        }else {
            var betweenMs = parseInt(new Date().getTime()) - parseInt(b);
            var  betweens = Math.round(betweenMs / 1000);
            var booleans=parseInt(cede_times)-betweens;
            if(booleans>0){
                that.attr("time",booleans);
                time=booleans;
                that.val("剩余"+(time)+"秒");
            }else{
                that.val("");
                that.val("重新发送");
                that.attr("disabled",false);
                that.removeClass('code_style');
                clearInterval(timer);
                that.attr("time",0);

            }

        }
    });
 }