How To Build WordPress Client App with React Native Part #12: Creating Categories Screen

Here, we are going to implement the Categories screen. This screen will contain the list of categories related to the article posts. And on clicking on these categories, we will navigate to the posts which are based on that respective category.

The implementation is simple. We are going to fetch the categories data and display it with the FlatList component. And by using the

TouchableOpacity 

First, we need to open the Categories.js file and import necessary components and define some required state as well as shown in the code snippet below:

import React from 'react';
import {
  FlatList,
  ScrollView,
  View,
  TouchableOpacity,
} from 'react-native';
export default class Categories extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      loading: false,
      categories: [],
    };
  }

Here, we have defined the loading state to display the loader on fetching of data and categories to store the categories list data. Now, we need to create a function called fetchCategorie() which will fetch all the categories data from the WordPress API as shown in the code snippet below:

componentDidMount() {
    this.fetchCategorie();
  }
  async fetchCategorie() {
    this.setState({ loading: true });
    const response = await fetch(`https://kriss.io/wp-json/wp/v2/categories`);
    const categories = await response.json();

    this.setState({
      categories: categories
    });
  }

Here, we have fetched the categories data using the fetch function. Then, we parse it to JSON and store it in the categories state. Then, we have called the function in the componentDidMount hook.

Now, we need to add the data to 

FlatList

render() {
    return (
      <ScrollView>
        <FlatList
          data={this.state.categories}
          renderItem={({item}) => (
            <TouchableOpacity
              onPress={() =>
                this.props.navigation.navigate('CategorieList', {
                  categorie_id: item.id,
                  categorie_name: item.name
                })
              }>
              <Card>
                <Card.Content>
                  <Title>{item.name}</Title>
                </Card.Content>
              </Card>
            </TouchableOpacity>
          )}
          keyExtractor={(item, index) => index}
        />
      </ScrollView>
    );
  }
}

Here, we have the template in the 

FlatList

FlatList

TouchableOpacity

CategorieList

Card

Hence, we will get the following result in the emulator screens:

As we can see, we have got the categories list in the Categories list. By tapping on any list item, we need to navigate to the CategorieList screen which will display the articles related to that category. But, we get error because we have not yet implemented the screen.

For that, we need to create a new screen called CategoriesList.js file in the

‘./screens/’

Then, we need to make the imports and also define state as shown in the code snippet below:

import React from 'react';
import {View, FlatList, TouchableOpacity} from 'react-native';
import {Card, Title, Paragraph} from 'react-native-paper';
import moment from 'moment';
import HTML from 'react-native-render-html';
export default class CategorieList extends React.Component {
  constructor(props) {
    super(props);

    this.state = {
      posts: [],
    };
  }

Here, we have defined the posts state which will store the posts fetched based in the category id.

Next, we need to add the CategorieList screen to the stack navigator in the App.js file. For that, we need to make use of the code from the following code snippet:

import CategorieList from './screens/CategoriesList';
const StackNavigator = createStackNavigator({
  DashboardTabNavigator: DashboardTabNavigator,
  SinglePost: SinglePost,
  CategorieList : CategorieList
});

Then, we need to implement the function called fetchPost which is used to fetch the article posts based on the particular category. The overall implementation of the function is provided in the code snippet below:

componentDidMount() {
   this.fetchPost();
 }

 async fetchPost() {
   let categorie_id = this.props.navigation.getParam('categorie_id');
   const response = await fetch(
     `https://kriss.io/wp-json/wp/v2/posts?categories=${categorie_id}`,
   );
   const post = await response.json();
   this.setState({posts: post});
 }

Here, we have fetched the posts using fetch() function from the WordPress API with category id value. Then, we parsed it and stored it in the posts state variable. Lastly, we called the function in the componentDidMount hook of the CategorieList screen.

Now, we need to set up the template of the CategorieList screen to display the list of article post based on the particular category. For that, we need to use the code from the following code snippet in the render() function

render() {
    categorie_title = this.props.navigation.getParam('title');
    return (
      <View>
        <Title style={{marginLeft: 30}} >{categorie_title}</Title>
        <FlatList
          data={this.state.posts}
          renderItem={({item}) => (
            <TouchableOpacity
              onPress={() =>
                this.props.navigation.navigate('SinglePost', {
                  post_id: item.id,
                })
              }>
              <Card>
                <Card.Content>
                  <Title>{item.title.rendered}</Title>
                  <Paragraph>
                    Published on {moment(item.date, 'YYYYMMDD').fromNow()}
                  </Paragraph>
                </Card.Content>
                <Card.Cover source={{uri: item.jetpack_featured_media_url}} />
                <Card.Content>
                  <HTML html={item.excerpt.rendered} />
                </Card.Content>
              </Card>
            </TouchableOpacity>
          )}
          keyExtractor={item => item.id}
        />
      </View>
    );
  }
}

Here, we have used the 

FlatList

Hence, we will get the following result in the emulator screens:

As we can see, we can successfully navigate to the CategorieList screen from the Categories screen. And by tapping on articles, we can navigate to the SinglePost screen.

Summary

In this chapter, we learned how to implement the overall UI of the Categories screen as well as the CategorieList screen. We learned how to fetch the categories of different posts from the WordPress API. Then, we implemented the navigation to the CategorieList screen where we learned how to fetch the articles post based on the category id and display them as a list. Then, by clicking on the article posts we navigated to the SinglePost screen.

This series intends to show how I build an app to serve content from my WordPress blog by using react-native. Since my blog is talking about react-native, the series and the articles are interconnected. We will learn how to set-up many packages that make our lives comfortable and learn how to deal with WordPress APIs. Here, the most prominent features talked about in the book are the dark theme, offline mode, infinite scroll and many more. You can discover much more in this series. this inspiration to do this tutorial series came from the React Native App Templates from instamobile