Firebase project setup in Android Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Firebase Project Initialization

What is the first step to connect your Android app to a Firebase project?

A Download the google-services.json file and place it anywhere in your project folder.

B Add Firebase dependencies to your build.gradle file before creating a Firebase project.

C Create a Firebase project in the Firebase console and register your Android app with its package name.

D Write Kotlin code to initialize Firebase in your MainActivity before creating a Firebase project.

💡 Hint

Think about what you need to do before adding code or files.

You must first create a Firebase project in the Firebase console and register your Android app using its package name. This generates the configuration file needed for your app.

❓ ui_behavior

intermediate

Placing google-services.json

Where should you place the google-services.json file in your Android project for Firebase to work correctly?

A In the app/ directory of your Android project.

B In the build/ directory.

C In the src/main/java/ directory.

D In the root directory of your Android project.

💡 Hint

It should be where your app module files are.

The google-services.json file must be placed inside the app/ directory (the module folder) so the Firebase Gradle plugin can find it during build.

📝 Syntax

advanced

Adding Firebase Plugin in build.gradle

Which line correctly applies the Firebase plugin in your app-level build.gradle file?

Android Kotlin

plugins {
    id("com.android.application")
    // Add Firebase plugin here
}

A apply plugin: 'firebase-google-services'

B apply plugin: 'com.google.gms.google-services'

C id("com.google.firebase")

D id("com.google.gms.google-services")

💡 Hint

Use the plugins block syntax with the correct plugin id.

The correct plugin id to apply in the plugins block is "com.google.gms.google-services". The other options are either old syntax or incorrect plugin ids.

❓ lifecycle

advanced

Firebase Initialization Timing

When is the best time to initialize Firebase in your Android app to ensure it works properly?

A In the onCreate() method of your Application class before any UI is created.

B In the onStart() method of your MainActivity after UI is visible.

C In the onResume() method of your MainActivity after user interaction.

D In a background thread after the app has fully loaded.

💡 Hint

Think about when Firebase services should be ready for use.

Initializing Firebase in the Application class's onCreate() ensures Firebase is ready before any activity or UI loads.

🔧 Debug

expert

Debugging Missing Firebase Configuration

Your app crashes with a runtime error saying "Default FirebaseApp is not initialized". Which of the following is the most likely cause?

A You did not add Firebase dependencies in the project-level build.gradle file.

B The google-services.json file is missing or placed in the wrong folder.

C You forgot to add internet permission in AndroidManifest.xml.

D You initialized Firebase twice in your Application class.

💡 Hint

Check if the configuration file is correctly included.

This error usually means the app cannot find the Firebase config file (google-services.json) or it is not placed in the correct location.

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