connectWillAppear: AppState implementation

class WrapperComponent extends Component {
  constructor(props) {
    super(props);
    this.state = {
      handledMounted: false,
      appState: null,
    };
    this.refHandler = this.refHandler.bind(this);
    this.handleAppStateChange = this.handleAppStateChange.bind(this);
    this.componentWillAppear = this.componentWillAppear.bind(this);
  }

  componentWillMount() {
    this.componentWillAppear();
    AppState.addEventListener('change', this.handleAppStateChange);
  }

  componentWillAppear() {
    if (this.instance) {
      if (!this.instance.componentWillAppear) {
        console.warn('You called connectFocus with a component that failed to implement componentWillAppear', this.instance);
      } else {
        this.instance.componentWillAppear();
      }
    }
  }

  componentWillUnmount() {
    AppState.removeEventListener('change', this.handleAppStateChange);
  }

  handleAppStateChange(newAppState) {
    if (this.state.appState !== newAppState && newAppState === 'active' && this.isComponentActive(this.props.activeComponent)) {
      this.componentWillAppear();
    }
    this.setState({
      appState: newAppState,
    });
  }
  
  . . . 
  
}