Firebase project setup in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize Firebase in your Android app's main activity.

Android Kotlin

override fun onCreate(savedInstanceState: Bundle?) {
  super.onCreate(savedInstanceState)
  setContentView(R.layout.activity_main)
  Firebase[1].initializeApp(this)
}

Drag options to blanks, or click blank then click option'

AApp

BAuth

CDatabase

DFirestore

Attempts:

3 left

💡 Hint

Common Mistakes

Using FirebaseAuth or FirebaseDatabase instead of FirebaseApp.

Forgetting to call initialize in onCreate.

You need to call FirebaseApp.initializeApp(this) to initialize Firebase in your app.

2fill in blank

medium

Complete the code to add Firebase Analytics to your app.

Android Kotlin

val analytics = FirebaseAnalytics[1](this)

Drag options to blanks, or click blank then click option'

A.setup

B.initialize

C.getInstance

D.create

Attempts:

3 left

💡 Hint

Common Mistakes

Using initialize or create instead of getInstance.

Not passing the context 'this' as parameter.

Use FirebaseAnalytics.getInstance(this) to get the Analytics instance.

3fill in blank

hard

Fix the error in the Firebase Realtime Database reference code.

Android Kotlin

val database = FirebaseDatabase.getInstance()
val myRef = database.[1]("message")

Drag options to blanks, or click blank then click option'

AgetRef

BgetReference

Cref

Dreference

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'reference' or 'ref' which are not methods.

Using 'getRef' which does not exist.

The correct method to get a database reference is getReference("message").

4fill in blank

hard

Fill both blanks to complete the Firebase Cloud Firestore initialization and get a collection reference.

Android Kotlin

val db = FirebaseFirestore[1]()
val usersRef = db.[2]("users")

Drag options to blanks, or click blank then click option'

AgetInstance

Bcollection

CgetCollection

Dinitialize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'initialize' instead of 'getInstance'.

Using 'getCollection' which is not a Firestore method.

Use FirebaseFirestore.getInstance() to get Firestore instance and collection("users") to get the collection reference.

5fill in blank

hard

Fill all three blanks to complete the Firebase Authentication sign-in with email and password code.

Android Kotlin

val auth = FirebaseAuth[1]()
auth.[2]WithEmailAndPassword(email, password)
  .addOnCompleteListener(this) { task ->
    if (task.[3]()) {
      // Sign in success
    } else {
      // Sign in failed
    }
  }

Drag options to blanks, or click blank then click option'

AgetInstance

Binstance

CisSuccessful

DsignIn

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'signIn' instead of 'getInstance' for first blank.

Using 'instance' instead of 'signIn' for second blank.

Checking 'task.success' instead of 'task.isSuccessful()'.

Use FirebaseAuth.getInstance() to get the auth instance, then signInWithEmailAndPassword to sign in, and check task.isSuccessful() to know if sign-in succeeded.

Practice

1. What is the first step to connect your Android app to Firebase?

easy

A. Add dependencies in the app's build.gradle file

B. Create a Firebase project in the Firebase console

C. Download the google-services.json file

D. Run the app on an emulator

Solution

1. Step 1: Access Firebase Console

   You need to start by creating a Firebase project in the Firebase console to link your app with Firebase services.

2. Step 2: Prepare for app integration

   Only after creating the project can you download configuration files and add dependencies.

3. Final Answer:

   Create a Firebase project in the Firebase console -> Option B

4. Quick Check:

   First step = Create Firebase project [OK]

Hint: Start by creating the Firebase project online [OK]

Common Mistakes:

• Trying to add dependencies before creating the project
• Downloading google-services.json before project setup
• Running app without Firebase configuration

2. Which line correctly adds the Firebase plugin in the project-level build.gradle file?

easy

A. classpath 'com.google.gms:google-services:4.3.15'

B. implementation 'com.google.firebase:firebase-analytics:21.3.0'

C. apply plugin: 'com.android.application'

D. compile 'com.google.firebase:firebase-core:16.0.9'

Solution

1. Step 1: Identify plugin declaration

   The Firebase plugin is added in the project-level build.gradle under dependencies using the classpath keyword.

2. Step 2: Match correct syntax

   classpath 'com.google.gms:google-services:4.3.15' uses classpath with the correct Firebase plugin version format.

3. Final Answer:

   classpath 'com.google.gms:google-services:4.3.15' -> Option A

4. Quick Check:

   Firebase plugin uses classpath in project build.gradle [OK]

Hint: Firebase plugin uses classpath, not implementation [OK]

Common Mistakes:

• Using implementation instead of classpath for plugin
• Adding plugin in app-level build.gradle instead of project-level
• Using outdated or incorrect plugin versions

3. Given this snippet in the app-level build.gradle file:

plugins {
    id 'com.android.application'
    id 'com.google.gms.google-services'
}
dependencies {
    implementation 'com.google.firebase:firebase-analytics:21.3.0'
}

What happens when you sync the project?

medium

A. The project syncs but Firebase Analytics is not included

B. Build fails because the google-services plugin is not applied correctly

C. The app runs without Firebase Analytics features

D. The Firebase Analytics library is added and the google-services plugin is applied successfully

Solution

1. Step 1: Check plugin application

   The plugin 'com.google.gms.google-services' is applied correctly in the plugins block, which is the modern way.

2. Step 2: Verify dependency inclusion

   The Firebase Analytics library is included in dependencies, so it will be added on sync.

3. Final Answer:

   The Firebase Analytics library is added and the google-services plugin is applied successfully -> Option D

4. Quick Check:

   Correct plugin + dependency = successful sync [OK]

Hint: Check plugins block for google-services plugin [OK]

Common Mistakes:

• Applying plugin in wrong Gradle file
• Forgetting to add Firebase dependencies
• Using old apply plugin syntax with plugins block

4. You added the google-services.json file but your app crashes on startup with a missing resource error. What is the likely cause?

medium

A. You forgot to add Firebase dependencies in build.gradle

B. You did not create a Firebase project in the console

C. The google-services.json file is placed in the wrong folder

D. You did not enable internet permission in AndroidManifest.xml

Solution

1. Step 1: Understand google-services.json placement

   This file must be placed in the app module folder (usually app/) to be recognized during build.

2. Step 2: Identify error cause

   If placed elsewhere, the build system cannot find required resources, causing crashes.

3. Final Answer:

   The google-services.json file is placed in the wrong folder -> Option C

4. Quick Check:

   Correct file location prevents resource errors [OK]

Hint: Place google-services.json inside the app folder [OK]

Common Mistakes:

• Putting google-services.json in the project root
• Not syncing project after adding the file
• Ignoring build errors related to Firebase

5. You want to add Firebase Authentication to your Android app. After creating the Firebase project and adding google-services.json, what is the correct sequence to set up your app?

hard

A. Add Firebase Auth dependency, apply google-services plugin, sync project, then initialize FirebaseAuth in code

B. Initialize FirebaseAuth in code, add dependency, apply plugin, then sync project

C. Apply google-services plugin, initialize FirebaseAuth in code, add dependency, then sync project

D. Sync project, add dependency, apply plugin, then initialize FirebaseAuth in code

Solution

1. Step 1: Add Firebase Auth dependency

   First, add the Firebase Authentication library in the app-level build.gradle dependencies.

2. Step 2: Apply google-services plugin and sync

   Apply the google-services plugin in the app-level build.gradle and sync the project to integrate Firebase services.

3. Step 3: Initialize FirebaseAuth in code

   Finally, initialize FirebaseAuth in your Kotlin code to use authentication features.

4. Final Answer:

   Add Firebase Auth dependency, apply google-services plugin, sync project, then initialize FirebaseAuth in code -> Option A

5. Quick Check:

   Dependency -> plugin -> sync -> code init [OK]

Hint: Add dependency and plugin before coding FirebaseAuth [OK]

Common Mistakes:

• Initializing FirebaseAuth before adding dependencies
• Forgetting to sync project after changes
• Applying plugin after coding initialization