在layout xml中给一个控件添加paddingStart属性但没有添加paddingEnd属性时，会有如下xml error： when you define paddingStart you should probably also define paddingEnd for right-to-left symmetry... 这句话是说paddingStart和paddingEnd需要成对出现，但是我并不太明白为什么一定要成对出现，求赐教。
In other words, paddingLeft and paddingRight must be used in pairs paddingStart and paddingEnd must be used in pairs PaddingLeft/Right and paddingStart/End must not be mixed
For example: paddingLeft and paddingEnd are mixed In the case of r2l, both parameters represent the padding on the left, there will be a conflict
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l2r: paddingStart=paddingLeft, paddingEnd=paddingRight
r2l: paddingStart=paddingRight, paddingEnd=paddingLeft
In other words, paddingLeft and paddingRight must be used in pairs
paddingStart and paddingEnd must be used in pairs
PaddingLeft/Right and paddingStart/End must not be mixed
For example:
paddingLeft and paddingEnd are mixed
In the case of r2l, both parameters represent the padding on the left, there will be a conflict