Method is not being invoked when i press the button

问题

I am using react navigation and have added a button on the right to signout from my app using default navigation options as shown below :

const otherApp = createStackNavigator({
  Welcome : { 
    screen : WelcomeScreen
  }
},
{
  defaultNavigationOptions : ({navigation}) => ({
    title : 'Welcome',
    headerStyle: {
      backgroundColor: '#29434e',
      shadowColor: 'transparent',
      elevation: 0
    },
    headerRight: (
      <TouchableOpacity
        style={{ backgroundColor: '#DDDDDD', padding: 5 }}
        onPress={() => navigation.getParam('logout')}>
        <Text
          style={{
            fontSize: 10,
          }}>
          Logout
        </Text>
      </TouchableOpacity>
    ),
  })
});

And i am binding the method to be invoked as follows :

_Logout() {
    this.props.signOut();
  }
  componentDidMount(){
    this.props.navigation.setParams({ logout : this._Logout.bind(this) })
  }

Function is maped to props using the redux

const mapDispatchToProps = (dispatch) => {
  return {
    Signout : ()=> dispatch(Signout())
  }
}

But the problem is when i press the button, it does not invoke the method !

回答1:

You can also use onFocus method of react-navigation to see whether the screen is on focus or not. If the screen is on focus then call the function.

import { withNavigation } from "react-navigation";
 componentDidMount() {
    const { navigation } = this.props;
    this.focusListener = navigation.addListener("didFocus", () => {
      // The screen is focused
      // Call any action
    });
  }

  componentWillUnmount() {
    // Remove the event listener
    this.focusListener.remove();
  }

export default withNavigation(Your Class Name);

Method : 2

import { NavigationEvents } from "react-navigation";

 onFocus = () => {
 //Write the code here which you want to do when the screen comes to focus.
  };

  render() {
    return (
        <NavigationEvents
          onDidFocus={() => {
            this.onFocus();
          }}
        />
)}

回答2:

I got the solution, what i was doing wrong that i wasn't passing a call back in the onPress of the button !

logoutFromFirebase = () => {
    this.props.Signout();
    this.props.navigation.navigate(this.props.user.uid ? 'App' : 'Auth')
  }
  componentDidMount(){
    this.props.navigation.setParams({ logout : this.logoutFromFirebase })
  }

And default navigation

defaultNavigationOptions : ({navigation}) => ({
    title : 'Welcome',
    headerStyle: {
      backgroundColor: '#29434e',
      shadowColor: 'transparent',
      elevation: 0
    },
    headerRight: (
      <TouchableOpacity
        style={{ backgroundColor: '#DDDDDD', padding: 5 }}
        onPress={navigation.getParam('logout' , () => Reactotron.log('Logout not callled'))}>
        <Text
          style={{
            fontSize: 10,
          }}>
          Logout
        </Text>
      </TouchableOpacity>
    ),
  })

And now it is working fine !

来源：https://stackoverflow.com/questions/57725635/method-is-not-being-invoked-when-i-press-the-button