ionic 自定义button的dropdowns效果

在工作中需要做一个“子菜单”的效果，因此写了一个dropdown的效果，代码如下

<a class="button button-clear" style="overflow: visible" ng-click="showDistrictList()">
	<span id="btnValue">不限</span><i class="icon ion-arrow-down-b" style="font-size: 14px;"></i>
	<ul class="list absolute district_class" 
style="z-index: 999;top:105%;left: 0px;width: 105%;display: none">
		<li class="item" ng-click="itemSelected($event)">
			不限
		</li>
		<li class="item" ng-click="itemSelected($event)">
			岳麓区
		</li>
		<li class="item" ng-click="itemSelected($event)">
			芙蓉区
		</li>
		<li class="item" ng-click="itemSelected($event)">
			天心区
		</li>
		<li class="item" ng-click="itemSelected($event)">
			开福区
		</li>

		<li class="item" ng-click="itemSelected($event)">
			雨花区
		</li>
		<li class="item" ng-click="itemSelected($event)">
			长沙县
		</li>
		<li class="item" ng-click="itemSelected($event)">
			望城县
		</li>
	</ul>
</a>