Login page using React Native

User login and authentication is a primary functionality. Let's see how to create a Login Page and authenticate user.

1. Creat a component

To create a login page we need an input components like Input boxes to enter username and password and Button component to submit values and invoke authentication functions.

import React, { Component } from "react";
import { View, TextInput, Button } from "react-native";
class LoginScreen extends Component{
    state = {
        phone: "",
        password: "",


        return <View>
                <TextInputplaceholder="Phone" style={styles.input} onChangeText={e => this.setState({ phone: e })}/>
                <TextInputplaceholder="Password" style={styles.input} onChangeText={e => this.setState({ password: e })}/>
                <Text style={styles.messagetext}>{this.state.message}</Text>
                <Button onPress={this.login}>Login</Button>
//Write your own css style here.
const styles = StyleSheet.create({....});
login screen

2. Define a login function

Here i am gonna do 3 important things.

1. Connect to a database.

2. Fetch Result

3. Process Result

The above three process done by using react native fetch method.It is same as browser fetch API.

    const {phone,password} = this.state;
    const query= {
                    //Write your query 
    const DB_ENDPOINT ="https://your-database-api-endpoint";
    const options = {
                      uri: DB_ENDPOINT,
                      headers: { 'Content-Type': 'application/json' },
                      method: 'POST',
                      body: JSON.stringify({ query })

    fetch(DB_ENDPOINT, options).then(resp => {
      return resp.json()
    }).then(res => {
      //Returned result maybe different for you.
        if (res.data.result) {
          this.setState({ message: "Successfully logged in" });
        } else {
          this.setState({ message: "Invalid credentials" });
      return res;
    }) .catch(() => {
      this.setState({ message: "Invalid credentials" });

3. Display result

Now we have to enter a phone number and password to login.The Authenticaiton result will be displayed in message text and then we need to navigate if the result is success.