行点击后显示黑点, 什么情况?

https://developers.weixin.qq.com/miniprogram/dev/devtools/minicode.html

弄成可复现的代码片段吧，没css挺难猜的

<view class="tr" 
bindtap="rowClick" 
data-row="{{x}}" 
data-idx="{{idx}}"          
style="background-color:{{selectedIdx == idx?'red':'white'}};color:{{selectedIdx == idx?'white':'black'}}"
>