HarmonyOS TextInput输入的时候，当文字达到一定数量的时候，自动关闭输入框

@Entry 
@Component 
struct FirstTest { 
  @State message1: string = 'Hello World'; 
  private controller:TextInputController = new TextInputController(); 
 
  build() { 
    Column() { 
      Text("FirstTest：" + this.message1) 
        .fontSize(25) 
        .fontWeight(FontWeight.Bold) 
 
      TextInput({placeholder:'Waiting for input',text:$$this.message1,controller:this.controller}) 
        .fontSize(25) 
        .fontWeight(FontWeight.Bold) 
        .onChange(()=>{ 
          if(this.message1.length >= 20){ 
            this.controller.stopEditing() 
          } 
        }) 
 
    } 
  } 
}