微信小程序 实现动态显示和隐藏某个控件
1.wxml：
<view>
<button bindtap="onChangeShowState">{{showView?'显示pieCanvas':'隐藏pieCanvas'}}</button>
</view>
<view class="{{showView?'view_show':'view_hide'}}">
<canvas canvas-id="pieCanvas" style="width:400px;height:280px;"></canvas>
</view><view>
<bu
