How do you integrate Firebase in an Android/iOS app?

Firebase - Interview Questions and Answers

Integrating Firebase in an Android/iOS App

Firebase provides various services like Authentication, Firestore, FCM, and more. Below is a step-by-step guide to integrating Firebase into an Android and iOS app.

Android Integration :

1. Create a Firebase Project

Go to Firebase Console.
Click "Add project", enter a name, and set up Google Analytics if needed.
Click "Create project".

2. Add Firebase to Your Android App

In Firebase Console, click "Add App" → Android.
Enter your app’s package name (e.g., com.example.myapp).
Download the google-services.json file and place it inside:
```
app/src/main/
```

Add Firebase SDK dependencies:

Open build.gradle (Project level):

dependencies {
    classpath 'com.google.gms:google-services:4.3.10' // Ensure latest version
}

Open build.gradle (Module level - app):

plugins {
    id 'com.google.gms.google-services' // Add this at the bottom
}

dependencies {
    implementation platform('com.google.firebase:firebase-bom:32.0.0')
    implementation 'com.google.firebase:firebase-analytics'
}

Sync Gradle and rebuild the project.

3. Initialize Firebase in Your Android App

In your MainActivity.kt (Kotlin):

import com.google.firebase.analytics.FirebaseAnalytics
import com.google.firebase.analytics.ktx.analytics
import com.google.firebase.ktx.Firebase

class MainActivity : AppCompatActivity() {
    private lateinit var firebaseAnalytics: FirebaseAnalytics

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Initialize Firebase Analytics
        firebaseAnalytics = Firebase.analytics
    }
}

iOS Integration :

1. Create a Firebase Project

(Same steps as Android)

2. Add Firebase to Your iOS App

In Firebase Console, click "Add App" → iOS.
Enter your app’s Bundle ID (e.g., com.example.myiosapp).
Download the GoogleService-Info.plist file.
Drag the GoogleService-Info.plist into the Xcode Runner directory.

3. Install Firebase SDK

Open Terminal and navigate to your project folder:
```
cd ios
pod init
```

Open the Podfile and add:

platform :ios, '10.0'
use_frameworks!
pod 'Firebase/Core'

Install dependencies:
```
pod install
```
Open the .xcworkspace file in Xcode.

4. Initialize Firebase in iOS

Open AppDelegate.swift and modify:

import UIKit
import Firebase

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        FirebaseApp.configure()
        return true
    }
}

Testing Firebase Integration

For Android:
```
adb logcat -s Firebase
```
For iOS:
```
Xcode → Run App → Debug Console
```

Common Firebase Services to Integrate Next

* Firebase Authentication – User login/sign-up
* Cloud Firestore – Real-time database
* Firebase Cloud Messaging (FCM) – Push notifications
* Firebase Remote Config – Dynamic app updates