代碼高亮

import React from 'react';
import { AsyncStorage, Linking, Platform, BackHandler } from 'react-native';
import { polyfill } from 'react-lifecycles-compat';

import {
  NavigationActions,
  pathUtils,
  getNavigation,
  NavigationProvider,
} from '@react-navigation/core';
import invariant from './utils/invariant';
import docsUrl from './utils/docsUrl';

const { urlToPathAndParams } = pathUtils;

function isStateful(props) {
  return !props.navigation;
}

function validateProps(props) {
  if (isStateful(props)) {
    return;
  }
  // eslint-disable-next-line no-unused-vars
  const { navigation, screenProps, ...containerProps } = props;

  const keys = Object.keys(containerProps);

  if (keys.length !== 0) {
    throw new Error(
      'This navigator has both navigation and container props, so it is ' +
        `unclear if it should own its own state. Remove props: "${keys.join(
          ', '
        )}" ` +
        'if the navigator should get its state from the navigation prop. If the ' +
        'navigator should maintain its own state, do not pass a navigation prop.'
    );
  }
}

// Track the number of stateful container instances. Warn if >0 and not using the
// detached prop to explicitly acknowledge the behavior. We should deprecated implicit
// stateful navigation containers in a future release and require a provider style pattern
// instead in order to eliminate confusion entirely.
let _statefulContainerCount = 0;
export function _TESTING_ONLY_reset_container_count() {
  _statefulContainerCount = 0;
}

// We keep a global flag to catch errors during the state persistence hydrating scenario.
// The innermost navigator who catches the error will dispatch a new init action.
let _reactNavigationIsHydratingState = false;
// Unfortunate to use global state here, but it seems necessesary for the time
// being. There seems to be some problems with cascading componentDidCatch
// handlers. Ideally the inner non-stateful navigator catches the error and
// re-throws it, to be caught by the top-level stateful navigator.

/**
 * Create an HOC that injects the navigation and manages the navigation state
 * in case it's not passed from above.
 * This allows to use e.g. the StackNavigator and TabNavigator as root-level
 * components.
 */
export default function createNavigationContainer(Component) {
  class NavigationContainer extends React.Component {
    subs = null;

    static router = Component.router;
    static navigationOptions = null;

    static getDerivedStateFromProps(nextProps) {
      validateProps(nextProps);
      return null;
    }

    _actionEventSubscribers = new Set();

    constructor(props) {
      super(props);

      validateProps(props);

      this._initialAction = NavigationActions.init();

      if (this._isStateful()) {
        this.subs = BackHandler.addEventListener('hardwareBackPress', () => {
          if (!this._isMounted) {
            this.subs && this.subs.remove();
          } else {
            // dispatch returns true if the action results in a state change,
            // and false otherwise. This maps well to what BackHandler expects
            // from a callback -- true if handled, false if not handled
            return this.dispatch(NavigationActions.back());
          }
        });
      }

      this.state = {
        nav:
          this._isStateful() && !props.persistenceKey
            ? Component.router.getStateForAction(this._initialAction)
            : null,
      };
    }

    _renderLoading() {
      return this.props.renderLoadingExperimental
        ? this.props.renderLoadingExperimental()
        : null;
    }

    _isStateful() {
      return isStateful(this.props);
    }

    _validateProps(props) {
      if (this._isStateful()) {
        return;
      }

      // eslint-disable-next-line no-unused-vars
      const { navigation, screenProps, ...containerProps } = props;

      const keys = Object.keys(containerProps);

      if (keys.length !== 0) {
        throw new Error(
          'This navigator has both navigation and container props, so it is ' +
            `unclear if it should own its own state. Remove props: "${keys.join(
              ', '
            )}" ` +
            'if the navigator should get its state from the navigation prop. If the ' +
            'navigator should maintain its own state, do not pass a navigation prop.'
        );
      }
    }

    _handleOpenURL = ({ url }) => {
      const { enableURLHandling, uriPrefix } = this.props;
      if (enableURLHandling === false) {
        return;
      }
      const parsedUrl = urlToPathAndParams(url, uriPrefix);
      if (parsedUrl) {
        const { path, params } = parsedUrl;
        const action = Component.router.getActionForPathAndParams(path, params);
        if (action) {
          this.dispatch(action);
        }
      }
    };

    _onNavigationStateChange(prevNav, nav, action) {
      if (
        typeof this.props.onNavigationStateChange === 'undefined' &&
        this._isStateful() &&
        !!process.env.REACT_NAV_LOGGING
      ) {
        if (console.group) {
          console.group('Navigation Dispatch: ');
          console.log('Action: ', action);
          console.log('New State: ', nav);
          console.log('Last State: ', prevNav);
          console.groupEnd();
        } else {
          console.log('Navigation Dispatch: ', {
            action,
            newState: nav,
            lastState: prevNav,
          });
        }
        return;
      }

      if (typeof this.props.onNavigationStateChange === 'function') {
        this.props.onNavigationStateChange(prevNav, nav, action);
      }
    }

    componentDidUpdate() {
      // Clear cached _navState every tick
      if (this._navState === this.state.nav) {
        this._navState = null;
      }
    }

    async componentDidMount() {
      this._isMounted = true;
      if (!this._isStateful()) {
        return;
      }

      if (__DEV__ && !this.props.detached) {
        if (_statefulContainerCount > 0) {
          // Temporarily only show this on iOS due to this issue:
          // https://github.com/react-navigation/react-navigation/issues/4196#issuecomment-390827829
          if (Platform.OS === 'ios') {
            console.warn(
              `You should only render one navigator explicitly in your app, and other navigators should be rendered by including them in that navigator. Full details at: ${docsUrl(
                'common-mistakes.html#explicitly-rendering-more-than-one-navigator'
              )}`
            );
          }
        }
      }
      _statefulContainerCount++;
      Linking.addEventListener('url', this._handleOpenURL);

      // Pull out anything that can impact state
      const { persistenceKey, uriPrefix, enableURLHandling } = this.props;
      let parsedUrl = null;
      let startupStateJSON = null;
      if (enableURLHandling !== false) {
        startupStateJSON =
          persistenceKey && (await AsyncStorage.getItem(persistenceKey));
        const url = await Linking.getInitialURL();
        parsedUrl = url && urlToPathAndParams(url, uriPrefix);
      }

      // Initialize state. This must be done *after* any async code
      // so we don't end up with a different value for this.state.nav
      // due to changes while async function was resolving
      let action = this._initialAction;
      let startupState = this.state.nav;
      if (!startupState) {
        !!process.env.REACT_NAV_LOGGING &&
          console.log('Init new Navigation State');
        startupState = Component.router.getStateForAction(action);
      }

      // Pull persisted state from AsyncStorage
      if (startupStateJSON) {
        try {
          startupState = JSON.parse(startupStateJSON);
          _reactNavigationIsHydratingState = true;
        } catch (e) {
          /* do nothing */
        }
      }

      // Pull state out of URL
      if (parsedUrl) {
        const { path, params } = parsedUrl;
        const urlAction = Component.router.getActionForPathAndParams(
          path,
          params
        );
        if (urlAction) {
          !!process.env.REACT_NAV_LOGGING &&
            console.log(
              'Applying Navigation Action for Initial URL:',
              parsedUrl
            );
          action = urlAction;
          startupState = Component.router.getStateForAction(
            urlAction,
            startupState
          );
        }
      }

      const dispatchActions = () =>
        this._actionEventSubscribers.forEach(subscriber =>
          subscriber({
            type: 'action',
            action,
            state: this.state.nav,
            lastState: null,
          })
        );

      if (startupState === this.state.nav) {
        dispatchActions();
        return;
      }

      // eslint-disable-next-line react/no-did-mount-set-state
      this.setState({ nav: startupState }, () => {
        _reactNavigationIsHydratingState = false;
        dispatchActions();
      });
    }

    componentDidCatch(e) {
      if (_reactNavigationIsHydratingState) {
        _reactNavigationIsHydratingState = false;
        console.warn(
          'Uncaught exception while starting app from persisted navigation state! Trying to render again with a fresh navigation state..'
        );
        this.dispatch(NavigationActions.init());
      } else {
        throw e;
      }
    }

    _persistNavigationState = async nav => {
      const { persistenceKey } = this.props;
      if (!persistenceKey) {
        return;
      }
      await AsyncStorage.setItem(persistenceKey, JSON.stringify(nav));
    };

    componentWillUnmount() {
      this._isMounted = false;
      Linking.removeEventListener('url', this._handleOpenURL);
      this.subs && this.subs.remove();

      if (this._isStateful()) {
        _statefulContainerCount--;
      }
    }

    // Per-tick temporary storage for state.nav

    dispatch = action => {
      if (this.props.navigation) {
        return this.props.navigation.dispatch(action);
      }

      // navState will have the most up-to-date value, because setState sometimes behaves asyncronously
      this._navState = this._navState || this.state.nav;
      const lastNavState = this._navState;
      invariant(lastNavState, 'should be set in constructor if stateful');
      const reducedState = Component.router.getStateForAction(
        action,
        lastNavState
      );
      const navState = reducedState === null ? lastNavState : reducedState;

      const dispatchActionEvents = () => {
        this._actionEventSubscribers.forEach(subscriber =>
          subscriber({
            type: 'action',
            action,
            state: navState,
            lastState: lastNavState,
          })
        );
      };

      if (reducedState === null) {
        // The router will return null when action has been handled and the state hasn't changed.
        // dispatch returns true when something has been handled.
        dispatchActionEvents();
        return true;
      }

      if (navState !== lastNavState) {
        // Cache updates to state.nav during the tick to ensure that subsequent calls will not discard this change
        this._navState = navState;
        this.setState({ nav: navState }, () => {
          this._onNavigationStateChange(lastNavState, navState, action);
          dispatchActionEvents();
          this._persistNavigationState(navState);
        });
        return true;
      }

      dispatchActionEvents();
      return false;
    };

    _getScreenProps = () => this.props.screenProps;

    render() {
      let navigation = this.props.navigation;
      if (this._isStateful()) {
        const navState = this.state.nav;
        if (!navState) {
          return this._renderLoading();
        }
        if (!this._navigation || this._navigation.state !== navState) {
          this._navigation = getNavigation(
            Component.router,
            navState,
            this.dispatch,
            this._actionEventSubscribers,
            this._getScreenProps,
            () => this._navigation
          );
        }
        navigation = this._navigation;
      }
      invariant(navigation, 'failed to get navigation');
      return (
        <NavigationProvider value={navigation}>
          <Component {...this.props} navigation={navigation} />
        </NavigationProvider>
      );
    }
  }

  return polyfill(NavigationContainer);
}