可以使用valueChanges和subscribe方法来监听formControl的值是否发生变化。在onFocusOut事件中，通过调用markAsDirty方法来标记表单已被修改。示例代码如下：

component.ts:

import { Component, OnInit } from '@angular/core';
import { FormControl } from '@angular/forms';

@Component({
  selector: 'app-root',
  template: `
    

      
    
  `
})
export class AppComponent implements OnInit {

  nameControl = new FormControl();

  ngOnInit() {
    // Watch for changes to the name control value
    this.nameControl.valueChanges.subscribe(value => {
      console.log('Value changed:', value);
    });
  }

  onFocusOut() {
    // Mark the form as dirty (if the value has changed)
    if (this.nameControl.dirty) {
      console.log('Form is dirty');
    }
  }

}

component.html: