DEV Community: Sathya7032

Why Some Packages Like Google Sign-In or Razorpay Don’t Work in Expo — And How to Fix It

Sathya7032 — Wed, 13 Aug 2025 06:17:06 +0000

If you’re building an app with React Native using Expo, you may notice some packages — like Google Sign-In or Razorpay — don’t work in the default setup.

This is normal. Let’s see why and how to fix it.

1. Why They Don’t Work
Expo has two workflows:

1.Managed Workflow (default)

Easy to start.
No access to Android/iOS native code.
You can only use features Expo already supports.

2.Bare Workflow

You get full native code access.
You can install any React Native library.

Google Sign-In **and **Razorpay require changes to native files like Android Gradle and iOS plist — which the Managed Workflow hides from you.

*2. How to Make Them Work *
You have two main options.

Option 1: Use Expo EAS Build with Config Plugins
Step 1 — Install the package
Example: Google Sign-In

npm install @react-native-google-signin/google-signin

Step 2 — Add its Config Plugin
If the library has a config plugin, add it to app.json or app.config.js:

{
  "expo": {
    "plugins": [
      "@react-native-google-signin/google-signin"
    ]
  }
}

Step 3 — Prebuild (generate native code)

npx expo prebuild

Step 4 — Build with EAS

npx eas build -p android   # for Android
npx eas build -p ios       # for iOS

Option 2: Eject to Bare Workflow
Step 1 — Eject your Expo app

npx expo eject
This creates android/ and ios/ folders.

Step 2 — Install the package
Example: Razorpay

npm install react-native-razorpay

Step 3 — Install iOS pods (if on Mac)

cd ios
pod install
cd ..

Step 4 — Follow native setup instructions
Open:

android/ in Android Studio → add the Razorpay SDK settings in build.gradle.
ios/ in Xcode → configure plist or frameworks as per library docs.

Step 5 — Run the app

npx react-native run-android
npx react-native run-ios

Understanding Variables in Java – The Basics Made Simple

Sathya7032 — Mon, 11 Aug 2025 07:21:11 +0000

In Java, variables are like containers where you can store data. Think of them as labeled boxes — you give them a name, put something inside, and later you can take it out or even replace it with something new.

What can you do with variables?
Store Data
You can keep values like numbers, text, or true/false in a variable.

int age = 25; // storing a number
String name = "John"; // storing text

Change Data
Variables can hold different values during the program’s execution.

age = 26; // changing the value of 'age'

Reuse Data
Instead of typing the same value again, you can use the variable.

System.out.println("My age is " + age);

Perform Calculations
You can use variables in math operations.

int sum = age + 4;

Improve Readability
Using variables makes your code easier to understand.

double pi = 3.14159; // easier to read than typing the number everywhere

public class VariablesExample {
    public static void main(String[] args) {
        // Storing data
        int age = 25;
        String name = "John";
        double height = 5.9;
        boolean isStudent = true;

        // Using variables
        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
        System.out.println("Height: " + height);
        System.out.println("Student: " + isStudent);

        // Changing data
        age = 26; // updating value
        System.out.println("Updated Age: " + age);

        // Calculations
        int yearsToRetire = 60 - age;
        System.out.println("Years to retire: " + yearsToRetire);
    }
}

Why http://10.0.2.2 Works Instead of localhost in Android Emulator (React Native + Spring Boot)

Sathya7032 — Mon, 11 Aug 2025 06:59:47 +0000

When I was connecting my React Native app (running in the Android emulator) to my Spring Boot backend on my computer, using:

fetch("http://localhost:8080/api")

…didn’t work. ❌
But when I changed it to:

fetch("http://10.0.2.2:8080/api")

…it worked perfectly. ✅

Why?

localhost inside the emulator points to the emulator itself — not your computer.
Your Spring Boot server is running on your computer, not inside the emulator.
10.0.2.2 is a special IP address in the Android emulator that acts like “localhost of your computer”.

Think of it like this:

localhost → talks to the emulator
10.0.2.2 → talks to your computer

When to Use It

Use 10.0.2.2 only for Android emulator.
For iOS simulator, you can still use localhost.
For real devices, use your computer’s local IP (e.g., 192.168.x.x).

what is a POJO?

Sathya7032 — Mon, 11 Aug 2025 06:38:48 +0000

POJO stands for Plain Old Java Object.

It’s just a normal Java class that:
Stores data using fields (variables)
Lets you get and set those values using methods (getters and setters)
Does not depend on any special library, framework, or Java rules

`public class Employee {
private String name;
private int age;

// Getter for name
public String getName() {
    return name;
}

// Setter for name
public void setName(String name) {
    this.name = name;
}

// Getter for age
public int getAge() {
    return age;
}

// Setter for age
public void setAge(int age) {
    this.age = age;
}

}
`

This Employee class is a POJO because:

It’s just plain Java code.
It’s not extending any special class.
It’s not implementing any special interface.
It’s not using any framework annotations or dependencies.