HarmonyOS ROW/COLUMN/FLEX组件里怎样设置每个组件的对齐方式？

@Entry  
@Component  
struct Index {  
  @State message: string = 'Hello World';  
  build() {  
    Stack() {  
      Row() {  
        Text(this.message)  
          .fontSize(20)  
          .fontWeight(FontWeight.Bold)  
      }.justifyContent(FlexAlign.Start)  
      .height('100%')  
      .width('100%')  
      Row() {  
        Text("你好啊")  
          .fontSize(20)  
          .fontWeight(FontWeight.Bold)  
      }.justifyContent(FlexAlign.Center)  
      .height('100%')  
      .width('100%')  
    }  
    .height('100%')  
    .width('100%')  
  }  
}