Developing a simple react native application

When you nest navigators, the screens of one navigator are rendered inside the screens of another. If there is a stack, switching to a different screen will cause a new screen to be displayed.

Navigators are in charge of making the switch between different screens. Numerous navigation types are supported by react-navigation, including stack, drawer, and tab navigators. In addition to navigating between screens, we can transfer information between them.

There will be several steps that we will walk through to achieve our goal in this tutorial.

First Step- Application development and module installation

1. Use the command below to create a new project.

$ npx react-native init react-navigation-routing --version 0.63.2

1. After that, go to the newly created directory by using the following command here:

$ cd react-navigation-routing

1. Use the following command to install the necessary packages:

npm install –save react-navigation react-navigation-stack react-native-reanimated react-native-gesture-handler react-native-screens react-native-vector-icons

1. Open the iOS or Android application, depending on your device respectively, using the following code:

$ npm run ios
$ npm run android

Second Step- Creating screens

We will create two screens:

• Home screen
• Workers screen: Contains names of workers.

It will be necessary for your app to start with the HomeScreen and another screen that we will name WorkersScreen. These two screens will be essential for us to navigate through.

Since there is already a file named App.js created upon running the terminal commands, we will copy the file's content and modify it in a file called HomeScreen.js that we create.

import React from 'react';
import { StyleSheet, Text, View } from 'react-native';
class HomeScreen extends React.Component {
  render() {
    return (
      <View style={{ flex: 1, alignItems: "center", justifyContent: "center" }}>
      <Text>You have some workers.</Text>
      </View>
    );
  }
}
export default HomeScreen;

Output:

You have some workers.

Now, copy the App.js content to a new file called WorkersScreen.js and modify it. On this screen, you will be able to add new workers.

import React from 'react';
import { StyleSheet, Text, View } from 'react-native';
class WorkersScreen extends React.Component {
  render() {
    return (
      <View style={{ flex: 1, alignItems: "center", justifyContent: "center" }}>
      <Text>Add new workers here!</Text>
      </View>
    );
  }
}
export default WorkersScreen;

Third Step - Navigating react screens using nested navigators

Nesting navigators are the same as standard nesting components in that it renders a navigator within a screen of another navigator. Nesting numerous navigators are frequently required to get the desired UI behaviour.

You'll utilize a StackNavigator inside a tab navigator to move between screens. In this regard, a StackNavigator is similar to a call stack in functionality. As you move through the screens, the one before it rises to the top of the stack of screens.

We need to open the app.js and then replace its content. The content that we'll replace with includes two screens that we created.

import 'react-native-gesture-handler';
import React from 'react';
import { StyleSheet } from 'react-native';
import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator } from '@react-navigation/stack';
import { createBottomTabNavigator } from "@react-navigation/bottom-tabs";
import { getFocusedRouteNameFromRoute } from "@react-navigation/native";
import HomeScreen from './HomeScreen';
import WorkersScreen from './WorkersScreen';
export const screenNames = {
  home: "HomeScreen",
  workers: "WorkersScreen",
};
const HomeScreen = createStackNavigator();
function HomeScreen() {
  return (
    <HomeScreen.Navigator
      headerMode="none"
      screenOptions={{
        gestureEnabled: true,
        gestureDirection: "horizontal",
      }}
      initialRouteName={screenNames.home}
    >
      <HomeScreen.Screen name={screenNames.home} component={Home} />
    </HomeScreen.Navigator>
  );
}
const WorkersScreen = createStackNavigator();
function WorkersScreen({ navigation, route }) {
  const tabHiddenRoutes = ["HomeScreen"];
  useEffect(() => {
    if (tabHiddenRoutes.includes(getFocusedRouteNameFromRoute(route))) {
      navigation.setOptions({ tabBarVisible: false });
    } else {
      navigation.setOptions({ tabBarVisible: true });
    }
  }, [navigation, route]);
  return (
    <WorkersScreen.Navigator
      headerMode="none"
      screenOptions={{
        gestureEnabled: true,
        gestureDirection: "horizontal",
      }}
      initialRouteName={screenNames.home}
    >
      <WorkersScreen.Screen name={screenNames.home} component={home} />
      <WorkersScreen.Screen
        name={screenNames.HomeScreen}
        component={HomeScreen}
      />
    </WorkersScreen.Navigator>
  );
}
const Tab = createBottomTabNavigator();
export default function Navigation() {
  return (
    <Tab.Navigator
      initialRouteName={screenNames.HomeScreen}
      tabBarOptions={{
        activeTintColor: "#688E26",
        inactiveTintColor: "#6C6C6C",
      }}
    >
      <Tab.Screen
        name={screenNames.HomeScreen}
        component={HomeScreenScreen}
        options={{
          tabBarLabel: "",
          tabBarIcon: ({ color, focused }) => (
            <Icon
              name={focused ? "ri-home-fill" : "ri-home-line"}
              size="24"
              color={color}
            />
          ),
        }}
      />
      <Tab.Screen
        name={screenNames.WorkersScreen}
        component={WorkersScreen}
        options={{
          abBarLabel: "",
          tabBarIcon: ({ color, focused }) => (
            <Icon
              name={focused ? "ri-information-fill" : "ri-information-line"}
              size="24"
              color={color}
            />
          ),
        }}
      />
    </Tab.Navigator>
  );
}

In the above code:

• In our App.js, we'll find that we added NavigationContainer, TabNavigator and StackNavigator to ease and allow navigation from one screen to another.
• We also added the two screens: HomeScreen and WorkersScreen.
• The stack navigator is nested in the tab navigator.

Fourth Step- Adding buttons

We will add buttons to switch between the two screens, if necessary. Many of its useful attributes will be transmitted down to our screen as long as the navigation object is included in the stack navigator.

Add the following code in the HomeScreen.js. This will add a button to the home screen. Repeat the same way to add another button in the WorkersScreen.js.

<Button
  title="Add new workers"
  onPress={() =>
    this.props.navigation.navigate('WokersScreen')
  }
/>

Now, in WorkersScreen.js, add a button for Home Screen:

<Button
  title="Home"
  onPress={() => this.props.navigation.navigate('HomeScreen')}
/>

Fifth Step- passing data to other screens using context

Let's create an array of potential workers, for example, Jeff, Kim, and Cal, and an empty array of the already existing workers. In addition, we will implement a feature that allows users to add new workers to their existing list of workers.

Add the possible workers and current workers to the component’s state in the WorkersScreen.js:

class App extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
      possibleWorkers: [
        'Jeff',
        'Kim',
        'Cal',
      ],
      currentWorkers: [],
    }
  }

}

Let's now add a function to move a possible Workers into the list of current Workers:

class App extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
      possibleWorkers: [
        'Jeff',
        'Kim',
        'Cal',
      ],
      currentWorkers: [],
    }
  }
  addWorker = (index) => {
    const {
      currentWorkers,
      possibleWorkers,
    } = this.state
    // Pull wokers out of possibleWorkers
    const addedwokers = possibleWorkers.splice(index, 1)
    // And put wokers in currentWorkers
    currentWorkers.push(addedwokers)
    // Finally, update the app state
    this.setState({
      currentWorkers,
      possibleWorkers,
    })
  }
}

Adding WorkersContext to App

To see our workers on HomeScreen.js, you'll need to add them to WorkersScreen.js first.

First, we create a new WorkersContext file and export it.

import React from 'react';
export const WorkersContext = React.createContext();

Add the WorkersContext:

import 'react-native-gesture-handler';
import React from 'react';
import { StyleSheet } from 'react-native';
import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator } from '@react-navigation/stack';
import { WorkersContext } from './WorkersContext';
import Home from './Home';
import Wokers from './Wokers';

Context.Provider components are used to encapsulate the NavigationContainer in a new context object so that any children in the component tree can subscribe to changes in the context of the application.

Consumers will only be able to access your data if you supply them with a value. Let us do that:

class App extends React.Component {

  render() {
    return (
      <WorkersContext.Provider
        value={
          {
            currentWorkers: this.state.currentWorkers,
            possibleWorkers: this.state.possibleWorkers,
            addWorker: this.addWorker
          }
        }
      >
       <NavigationContainer>
       //...
      </WorkersContext.Provider>
    );
  }
}

HomeScreen and WokersScreen can now refer to current workers and possible workers in the event of any context changes.

Adding WorkersContext to HomeScreen

This step will set the application to display the current number of workers.

import React from 'react';
import { StyleSheet, Text, View, Button } from 'react-native';
import { WorkersContext } from './WorkersContext';
class HomeScreen extends React.Component {
  //...
}
HomeScreen.contextType = WorkersContext;
//...

The Class.contextType allows access context in our screens. For instance, let’s make our HomeScreen display how many current Workers we have:

import React from 'react';
import { StyleSheet, Text, View, Button } from 'react-native';
import { WorkersContext } from './WorkersContext';
class Home extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        <Text>You have { this.context.currentWorkers.length } wokers!</Text>
        <Button
          title="Add some wokers"
          onPress={() =>
            this.props.navigation.navigate('Workers')
          }
        />
      </View>
    );
  }
}
HomeScreen.contextType = WorkersContext;
//...

Output:

 You have 0 workers!.

Adding WorkersContext to WokersScreen

This step will set up the application to display the possible workers and provide buttons for adding them to the current workers.

import React from 'react';
import { StyleSheet, Text, View, Button } from 'react-native';
import { WorkersContext } from './WorkersContext';
class Workers extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        <Text>Add wokers here!</Text>
        {
          this.context.possibleWorkers.map((worker, index) => (
            <Button
              key={ worker }
              title={ `Add ${ worker }` }
              onPress={() =>
                this.context.addWorker(index)
              }
            />
          ))
        }
        <Button
          title="Back to home"
          onPress={() =>
            this.props.navigation.navigate('Home')
          }
        />
      </View>
    );
  }
}
WorkersScreen.contextType = WorkersContext;
//...

Conclusion

In this tutorial, we build a multi-screen React Native app. We figured out how to navigate between screens using React Navigation. We also created a mechanism for transferring data between screens using React Context.