说明：左边是正常版本，右边是拍平版本
justify-content: center
justify-content: flex-start
justify-content: flex-end
justify-content: space-between
justify-content: space-around
justify-content: space-evenly
scroll-view 组件
justify-content：center 和 space-between
setProperty 设置与 getPropertyValue 获取
justify-content
设置值: {{data.justifyContent}}
获取值: {{data.justifyContentActual}}
拍平
设置值: {{data.justifyContent}}
获取值: {{data.justifyContentActualFlat}}
第一个枚举值，'' (空字符串) - 空值情况