官方文档：https://reactnative.dev/docs/flexbox/#absolute--relative-layout
另外一片文档：https://medium.com/wix-engineering/the-full-react-native-layout-cheat-sheet-a4147802405c
需要注意的是position的relative的含义：它是先计算没有设定position的时候的位置，然后基于这个位置再加上top, bottom, left, right的值得到的结果，不是简单的根据sibling计算的。
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As a newbie in React Native I found myself time after time going back to React Native layout docs, struggling to understand and master the difference between all the different props. justify vs align, relative vs absolute, items vs content, It was all very confusing…