反应-传递道具，导航器中的设置错误？

Question

I am trying different ways to pass props between files. I am very new to react and very bad at it so I don't understand what I'm doing wrong or the different ways of sending it. Either way, it works between 'main' and 'favplaces' but not between login and main, which makes me think it has something to do with how App is set up. If I log the params that I got from Login in main then I'm getting either undefined or the app is crashing saying "undefined is not an object".

App:

const mainOptions = SwitchNavigator({
  main : Main,
  favPlaces : favPlaces,

})
const introStack = StackNavigator({
  logIn : LogIn,
  register : Register
})

const SwNavigator = SwitchNavigator({
  login : introStack,
  main : mainOptions

})

Login:

   constructor(props){
        super(props);
        this.state={
            username: "",
            password:"",

        }
        this.signIn = this.signIn.bind(this);
        this.navigate = this.props.navigation.navigate;
        this.params = this.props.navigation.state.params;
      }
     {......}
  signIn(){
        console.log("username", this.state.username)

        this.navigate({
    routeName: 'main',
    key: 'main',
    params: {
       username: this.state.username
    }
 });
  }

Main:

    constructor(props) {
            super(props);
        this.navigate = this.props.navigation.navigate;
        this.params = this.props.navigation.state.params;
    }
 handleClickFavourite = () => {
   console.log(this.state.latitude)
   this.navigate({
   routeName: 'favPlaces',
   key: 'favPlaces',
   params: {
      latitude: this.state.latitude
   }
});   

}

favPlace:

    constructor(props){
        super(props);
        this.navigate = this.props.navigation.navigate;
        this.params = this.props.navigation.state.params;
      }

   render()
      console.log("1", this.props.navigation.state.params.latitude);
      console.log("2", this.params.latitude);

both of these logs work.

Answer 1

I managed to get it to work. I removed the mainOptions navigator and changed the navigators to this:

const introStack = StackNavigator({
  loggingIn : LoggingIn,
  register : Register
})

const SwNavigator = SwitchNavigator({
  //login : introStack,
  loggingIn : introStack,
  main : Main,
  favPlaces : favPlaces,
  register : Register

})