react native navigation page blur

componentDidMount() {
    this.subs = [
      this.props.navigation.addListener('didFocus', () => this.didFocus()),
      this.props.navigation.addListener('willBlur', () => this.willBlur()),
    ];
  }
  componentWillUnmount() {
    this.subs.forEach(sub => sub.remove());
    this.willBlur();
  }
  didFocus() {
    //bla
  }
  willBlur() { 
    //bla
  }