HarmonyOS 鸿蒙Next %s、%d这种动态更新文本的方法是如何实现的？

[@Entry](/user/Entry)
[@Component](/user/Component)
struct Index {
  // 倒计时
  [@State](/user/State) countdown: number = 60;
  // 属性字符串
  mutableStyledString: MutableStyledString = new MutableStyledString(getContext().resourceManager.getStringSync($r('app.string.str_retry'),this.countdown));
  controller: TextController = new TextController();
async onPageShow() {
this.controller.setStyledString(this.mutableStyledString)
}
// 开始倒计时
aboutToAppear() {
setInterval(() => {
this.countdown–;
this.mutableStyledString = new MutableStyledString(getContext().resourceManager.getStringSync($r(‘app.string.str_retry’),this.countdown));
this.controller.setStyledString(this.mutableStyledString)
}, 1000)
}
build() {
Column() {
Text(undefined, { controller: this.controller }).key(‘mutableStyledString’) // 始终显示“请在%d秒后重试”
// Text($r(‘app.string.str_retry’, this.countdown)) // 显示“请在60秒后重试”且正常倒数
}
}
} 

{“name”: “str_retry”,“value”: “请在%d秒后重试”},this.countdown这个应该是getStringSync这个方法的参数而不是$r()的参数，位置放错了；另外每次数值变化都要重新赋值