react native Flatlist navigation

问题:

I m getting error TypeError: Cannot read property 'navigation' of undefined. I don't understand how to pass navigation component into each child so when a user presses an item it can navigate to employeeEdit component using React Navigation. i am newbie sorry if this is obvious.

import React, { Component } from 'react';
import { FlatList } from 'react-native';
import { connect } from 'react-redux';
//import { R } from 'ramda';
import _ from 'lodash';
import { employeesFetch } from '../actions';
import { HeaderButton } from './common';
import ListEmployee from './ListEmployee';


class EmployeeList extends Component {
  static navigationOptions = ({ navigation }) => ({
    headerRight: (
      <HeaderButton onPress={() => navigation.navigate('employeeCreate')}>
        Add
      </HeaderButton>
    )
  });

  componentWillMount() {
    this.props.employeesFetch();
  }

  keyExtractor(item) {
    return item.uid;
  }
  renderItem({ item }) {
    return <ListEmployee employee={item} navigation={this.props.navigation} />;
  }
  render() {
    return (
      <FlatList
      data={this.props.employees}
      renderItem={this.renderItem} // Only for test
      keyExtractor={this.keyExtractor}
      navigation={this.props.navigation}
      />
    );
  }
}
const mapStateToProps = (state) => {
  const employees = _.map(state.employees, (val, uid) => ({ ...val, uid }));
  return { employees };
};

export default connect(mapStateToProps, { employeesFetch })(EmployeeList);

Here's the code for ListEmployee

import React, { Component } from 'react';
import {
  Text,
  StyleSheet,
  TouchableWithoutFeedback,
  View
} from 'react-native';
import { CardSection } from './common';

class ListEmployee extends Component {

  render() {
  const { employee } = this.props;
  const { navigate } = this.props.navigation;
  const { textStyle } = styles;
  const { name } = this.props.employee;
    return (
      <TouchableWithoutFeedback onPress={() => navigate('employeeEdit', { employee })}>
        <View>
          <CardSection>
            <Text style={textStyle}>{name}</Text>
          </CardSection>
        </View>
      </TouchableWithoutFeedback>
    );
  }
}

/**
 second argument in connect does 2 things. 1.  dispatches all actions creators
return action objects to the store to be used by reducers; 2. creates props
of action creators to be used by components
**/
export default ListEmployee;

const styles = StyleSheet.create({
  textStyle: {
    fontSize: 18,
    paddingLeft: 15,
  }
});

回答1:

Inside you renderItem method, you can manage what happen when the user press one item of your FlatList:

renderItem({ item }) {
    <TouchableOpacity onPress={() => { this.props.navigator.push({id: 'employeeEdit'})}} >
        <ListEmployee employee={item} navigation={this.props.navigation} />
    </TouchableOpacity>
}

Hope it help you!

回答2:

This is one ES6 common pitfall. Don't worry my friend, you only have to learn it once to avoid them all over again.

Long story short, when you declare a method inside React Component, make it arrow function

So, change from this.

renderItem({ item }) {

to this

renderItem = ({ item }) => {

That should solve your problem, for some inconvenient reason, you can only access "this" if you declare your method as an arrow function, but not with normal declaration.

In your case, since renderItem is not an arrow function, "this" is not referred to the react component, therefore "this.props" is likely to be undefined, that is why it gave you this error Cannot read property 'navigation' of undefined since

this.props.navigation = (undefined).navigation