react-navigation/src/views/Drawer/DrawerSidebar.js

import React from 'react';
import { StyleSheet, View } from 'react-native';

import NavigationActions from '../../NavigationActions';
import StackActions from '../../routers/StackActions';
import invariant from '../../utils/invariant';

/**
 * Component that renders the sidebar screen of the drawer.
 */

class DrawerSidebar extends React.PureComponent {
  _getScreenOptions = routeKey => {
    const descriptor = this.props.descriptors[routeKey];
    invariant(
      descriptor.options,
      'Cannot access screen descriptor options from drawer sidebar'
    );
    return descriptor.options;
  };

  _getLabel = ({ focused, tintColor, route }) => {
    const { drawerLabel, title } = this._getScreenOptions(route.key);
    if (drawerLabel) {
      return typeof drawerLabel === 'function'
        ? drawerLabel({ tintColor, focused })
        : drawerLabel;
    }

    if (typeof title === 'string') {
      return title;
    }

    return route.routeName;
  };

  _renderIcon = ({ focused, tintColor, route }) => {
    const { drawerIcon } = this._getScreenOptions(route.key);
    if (drawerIcon) {
      return typeof drawerIcon === 'function'
        ? drawerIcon({ tintColor, focused })
        : drawerIcon;
    }
    return null;
  };

  _onItemPress = ({ route, focused }) => {
    if (!focused) {
      let subAction;
      // TODO (v3): Revisit and repeal this behavior:
      // if the child screen is a StackRouter then always navigate to its first screen (see #1914)
      if (route.index != null && route.index !== 0) {
        subAction = StackActions.reset({
          index: 0,
          actions: [
            NavigationActions.navigate({
              routeName: route.routes[0].routeName,
            }),
          ],
        });
      }
      this.props.navigation.dispatch(
        NavigationActions.navigate({
          routeName: route.routeName,
          action: subAction,
        })
      );
    }
  };

  render() {
    const ContentComponent = this.props.contentComponent;
    if (!ContentComponent) {
      return null;
    }
    const { state } = this.props.navigation;
    invariant(typeof state.index === 'number', 'should be set');
    return (
      <View style={[styles.container, this.props.style]}>
        <ContentComponent
          {...this.props.contentOptions}
          navigation={this.props.navigation}
          descriptors={this.props.descriptors}
          items={state.routes}
          activeItemKey={
            state.routes[state.index] ? state.routes[state.index].key : null
          }
          screenProps={this.props.screenProps}
          getLabel={this._getLabel}
          renderIcon={this._renderIcon}
          onItemPress={this._onItemPress}
          drawerPosition={this.props.drawerPosition}
        />
      </View>
    );
  }
}

export default DrawerSidebar;

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
});