Remote Config in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get an instance of Firebase Remote Config.

Android Kotlin

val remoteConfig = FirebaseRemoteConfig.[1]()

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

Astart

Binitialize

Ccreate

DgetInstance

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'initialize()' instead of 'getInstance()' causes a compile error.

Trying to create a new Remote Config object directly.

The getInstance() method returns the singleton instance of Firebase Remote Config.

2fill in blank

medium

Complete the code to set default values from an XML resource file named 'remote_config_defaults'.

Android Kotlin

remoteConfig.[1](R.xml.remote_config_defaults)

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

AsetDefaults

BsetDefaultsAsync

CapplyDefaults

DloadDefaults

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'setDefaultsAsync' which does not exist.

Using 'loadDefaults' which is not a Remote Config method.

The setDefaults() method sets default parameter values from an XML resource.

3fill in blank

hard

Fix the error in the code to fetch Remote Config values with a 1-hour cache expiration.

Android Kotlin

remoteConfig.fetch([1]).addOnCompleteListener { task ->
    if (task.isSuccessful) {
        remoteConfig.activate()
    }
}

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

A60

B3600

C3600000

D600

Attempts:

3 left

💡 Hint

Common Mistakes

Using milliseconds instead of seconds causes the cache to expire too late.

Using too small a number causes frequent fetches.

The fetch() method expects cache expiration in seconds. 3600 seconds equals 1 hour.

4fill in blank

hard

Fill both blanks to get a Remote Config string value for the key 'welcome_message'.

Android Kotlin

val welcomeMessage = remoteConfig.[1]("[2]")

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

AgetString

BgetValue

Cwelcome_message

DwelcomeMessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'getValue' returns a Remote Config value object, not a string.

Using a variable name instead of the key string.

Use getString() to get the string value for the key "welcome_message".

5fill in blank

hard

Fill all three blanks to fetch, activate, and then print the Remote Config value for 'feature_enabled'.

Android Kotlin

remoteConfig.[1]().addOnCompleteListener { task ->
    if (task.isSuccessful) {
        remoteConfig.[2]()
        println(remoteConfig.[3]("feature_enabled"))
    }
}

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

Afetch

Bactivate

CgetString

DfetchAndActivate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'fetchAndActivate' instead of separate fetch and activate calls.

Using 'getValue' instead of 'getString' to get the parameter value.

First, fetch() gets the latest values. Then activate() applies them. Finally, getString() retrieves the value for the key.

Practice

1. What is the main purpose of Firebase Remote Config in an Android app?

easy

A. To manage user authentication and login

B. To store user data locally on the device

C. To change app behavior and appearance without releasing a new app version

D. To handle app crashes and error reporting

Solution

1. Step 1: Understand Remote Config functionality

   Remote Config allows developers to update app behavior remotely without requiring users to download a new version.

2. Step 2: Compare options with Remote Config purpose

   Options B, C, and D relate to other Firebase services, not Remote Config.

3. Final Answer:

   To change app behavior and appearance without releasing a new app version -> Option C

4. Quick Check:

   Remote Config = Change app behavior remotely [OK]

Hint: Remote Config updates app without new installs [OK]

Common Mistakes:

• Confusing Remote Config with local data storage
• Mixing Remote Config with authentication features
• Thinking Remote Config handles crash reports

2. Which Kotlin code snippet correctly fetches and activates Remote Config values asynchronously?

easy

A. remoteConfig.fetchAndActivate().addOnCompleteListener { task -> if (task.isSuccessful) { applyConfig() } }

B. remoteConfig.fetch().activate()

C. remoteConfig.activate().fetch()

D. remoteConfig.fetchAndActivate { applyConfig() }

Solution

1. Step 1: Identify correct method chaining for fetch and activate

   The correct method is fetchAndActivate() which returns a Task to listen for completion.

2. Step 2: Check syntax for asynchronous handling

   remoteConfig.fetchAndActivate().addOnCompleteListener { task -> if (task.isSuccessful) { applyConfig() } } uses addOnCompleteListener properly to handle success and then apply config.

3. Final Answer:

   remoteConfig.fetchAndActivate().addOnCompleteListener { task -> if (task.isSuccessful) { applyConfig() } } -> Option A

4. Quick Check:

   fetchAndActivate() with listener = remoteConfig.fetchAndActivate().addOnCompleteListener { task -> if (task.isSuccessful) { applyConfig() } } [OK]

Hint: Use fetchAndActivate() with addOnCompleteListener [OK]

Common Mistakes:

• Calling activate() before fetch()
• Using fetch() and activate() separately without chaining
• Passing a lambda directly to fetchAndActivate()

3. Given this Kotlin code snippet, what will be printed if the Remote Config parameter "welcome_message" is not set remotely and default is "Hello"?

val welcome = remoteConfig.getString("welcome_message")
println(welcome)

medium

A. Hello

B. null

C. An empty string

D. welcome_message

Solution

1. Step 1: Understand getString behavior with default values

   If the parameter is not set remotely, Remote Config returns the default value provided in app defaults.

2. Step 2: Recognize default value is "Hello"

   The default for "welcome_message" is "Hello", so getString returns "Hello".

3. Final Answer:

   Hello -> Option A

4. Quick Check:

   Missing remote value returns default string [OK]

Hint: Missing remote key returns default value [OK]

Common Mistakes:

• Expecting null instead of default
• Assuming empty string if not set
• Confusing key name with value

4. What is wrong with this Kotlin code snippet for fetching Remote Config values?

remoteConfig.fetchAndActivate()
println(remoteConfig.getString("feature_flag"))

medium

A. fetchAndActivate() must be called on the main thread

B. feature_flag key must be an integer, not string

C. fetchAndActivate() requires a callback parameter

D. getString() is called before fetchAndActivate() completes

Solution

1. Step 1: Analyze asynchronous fetchAndActivate call

   fetchAndActivate() runs asynchronously, so calling getString immediately after may use old values.

2. Step 2: Identify missing completion handling

   Code lacks a listener or await to ensure fetchAndActivate finished before reading values.

3. Final Answer:

   getString() is called before fetchAndActivate() completes -> Option D

4. Quick Check:

   Must wait for fetchAndActivate() completion [OK]

Hint: Wait for fetchAndActivate() to finish before reading values [OK]

Common Mistakes:

• Assuming fetchAndActivate() is synchronous
• Not adding completion listeners
• Confusing key types

5. You want to show a special promotion banner only to 30% of your users using Remote Config. Which approach is best to implement this in Kotlin?

hard

A. Fetch a random number in app and show banner if number < 0.3

B. Create a Remote Config parameter "show_promo" with boolean true/false and use Firebase percentage rollout targeting

C. Use a local SharedPreferences flag to randomly enable banner for 30% users

D. Hardcode banner visibility in app and update app version for changes

Solution

1. Step 1: Understand Remote Config targeting features

   Firebase Remote Config supports percentage rollouts to control feature exposure to a subset of users.

2. Step 2: Choose parameter with percentage rollout

   Setting a boolean parameter "show_promo" with percentage targeting is the best practice for controlled rollout.

3. Final Answer:

   Create a Remote Config parameter "show_promo" with boolean true/false and use Firebase percentage rollout targeting -> Option B

4. Quick Check:

   Use Remote Config percentage rollout for user targeting [OK]

Hint: Use Remote Config percentage rollout, not local random logic [OK]

Common Mistakes:

• Using local random logic instead of Remote Config targeting
• Hardcoding feature flags requiring app updates
• Ignoring Remote Config's built-in user segmentation