HarmonyOS TextInput如何设置placeholder居右显示

@Entry  
@Component  
struct Index {  
  @State message: string = 'Hello World';  
  @State isEdit: boolean = false;  
  build() {  
      Row() {  
        Column() {  
          Text(this.message)  
            .fontSize(50)  
            .fontWeight(FontWeight.Bold)  
          TextInput({placeholder: this.isEdit?'':'我想要居右显示'})  
            .textAlign(this.isEdit?TextAlign.Start:TextAlign.End)  
            .onEditChange(isEdit=>{  
              this.isEdit = isEdit;  
            })  
        }  
        .width('100%')  
      }  
    .height('100%')  
  }  
}