SavedStateHandle in Android Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

SavedStateHandle preserves UI state on configuration change

Consider a ViewModel using SavedStateHandle to store a counter value. What will be the value of counter after a device rotation if the user incremented it to 5 before rotation?

Android Kotlin

class CounterViewModel(private val state: SavedStateHandle) : ViewModel() {
  var counter: Int
    get() = state.get<Int>("counter") ?: 0
    set(value) = state.set("counter", value)
}

// User increments counter to 5, then rotates device.

A counter will increment automatically to 6 after rotation

B counter will remain 5 after rotation

C counter will be null after rotation causing crash

D counter will reset to 0 after rotation

💡 Hint

SavedStateHandle keeps data across configuration changes like rotation.

SavedStateHandle stores data in a bundle that survives configuration changes, so the counter value 5 is preserved after rotation.

❓ lifecycle

intermediate

When is SavedStateHandle data cleared?

At what point is the data stored in SavedStateHandle cleared automatically by the Android system?

A When the ViewModel is cleared after the associated UI is destroyed permanently

B When the app process is killed by the system

C When the device is rotated

D When the user presses the back button once

💡 Hint

Think about the lifecycle of ViewModel and when it is destroyed.

SavedStateHandle data is cleared when the ViewModel is cleared, which happens when the UI is permanently destroyed, not on rotation or temporary events.

📝 Syntax

advanced

Correct way to retrieve a nullable value from SavedStateHandle

Which option correctly retrieves a nullable String value named "username" from SavedStateHandle in Kotlin?

Android Kotlin

val username: String? = savedStateHandle.???

A getOrDefault("username", "")

B getValue("username")

C get<String>("username")

D getNullable("username")

💡 Hint

Check the official SavedStateHandle API for retrieving values.

The method get(key) returns a nullable value of type T or null if not present. Other methods do not exist or have different signatures.

🔧 Debug

advanced

Why does this SavedStateHandle update not persist after process death?

Given this code snippet, why does the updated value not persist after the app process is killed and restarted?

savedStateHandle["score"] = 10
// app is killed and restarted
val score = savedStateHandle.get("score") ?: 0

A The value 10 is not serializable and cannot be saved

B The ViewModel was not recreated properly after restart

C The key "score" is invalid and cannot be saved

D SavedStateHandle only saves data during configuration changes, not process death

💡 Hint

Think about what SavedStateHandle is designed to save and what it is not.

SavedStateHandle saves data to survive configuration changes but does not persist data across process death. For that, you need persistent storage.

🧠 Conceptual

expert

How does SavedStateHandle integrate with Jetpack Navigation component?

Which statement best describes how SavedStateHandle works with Jetpack Navigation to pass and save UI state between destinations?

A SavedStateHandle automatically saves and restores navigation arguments and state when navigating between destinations

B SavedStateHandle requires manual serialization of navigation arguments to bundles before navigation

C SavedStateHandle cannot be used with Jetpack Navigation and is only for ViewModel internal state

D SavedStateHandle only works with fragments, not with navigation components

💡 Hint

Consider how navigation arguments and SavedStateHandle share data.

Jetpack Navigation integrates with SavedStateHandle to automatically save and restore navigation arguments and UI state across configuration changes and process death (if saved in saved state registry).

Practice

1.

What is the main purpose of SavedStateHandle in Android Kotlin?

easy

A. To save and restore small UI-related data automatically during configuration changes

B. To manage database connections

C. To handle network requests

D. To create UI layouts dynamically

Solution

1. Step 1: Understand the role of SavedStateHandle

   SavedStateHandle is designed to save small pieces of data like UI state during configuration changes such as screen rotations.

2. Step 2: Compare with other options

   Options A, B, and D relate to network requests, database connections, and UI layout creation, which are not the purpose of SavedStateHandle.

3. Final Answer:

   To save and restore small UI-related data automatically during configuration changes -> Option A

4. Quick Check:

   SavedStateHandle saves UI state = C [OK]

Hint: Remember: SavedStateHandle saves UI data on config changes [OK]

Common Mistakes:

• Confusing SavedStateHandle with database or network management
• Thinking it manages large data or files
• Assuming it creates UI layouts

2.

Which of the following is the correct way to store a value "username" in SavedStateHandle named savedStateHandle?

?

easy

A. savedStateHandle.put("username", "John")

B. savedStateHandle.set("username", "John")

C. savedStateHandle.save("username", "John")

D. savedStateHandle.store("username", "John")

Solution

1. Step 1: Recall SavedStateHandle API methods

   The correct method to store data is set(key, value).

2. Step 2: Check method names in options

   Only savedStateHandle.set("username", "John") uses set, others use incorrect method names.

3. Final Answer:

   savedStateHandle.set("username", "John") -> Option B

4. Quick Check:

   Use set() to store data = A [OK]

Hint: Use set() to save data in SavedStateHandle [OK]

Common Mistakes:

• Using put(), save(), or store() which do not exist
• Confusing with SharedPreferences methods
• Forgetting to use quotes around keys

3.

Given the code below, what will be the output of println(savedStateHandle.get<String>("name"))?

val savedStateHandle = SavedStateHandle()
savedStateHandle.set("name", "Alice")
savedStateHandle.set("age", 30)
savedStateHandle.set("name", "Bob")

medium

A. null

B. Alice

C. Bob

D. 30

Solution

1. Step 1: Analyze the set operations

   The key "name" is first set to "Alice", then overwritten with "Bob".

2. Step 2: Determine the value returned by get

   Getting "name" returns the latest value, which is "Bob".

3. Final Answer:

   Bob -> Option C

4. Quick Check:

   Last set value returned = A [OK]

Hint: Last set value for a key is returned by get() [OK]

Common Mistakes:

• Assuming first set value is returned
• Confusing key names
• Expecting numeric value for string key

4.

Identify the error in the following code snippet using SavedStateHandle:

val savedStateHandle = SavedStateHandle()
savedStateHandle.set("count", 10)
val count: String = savedStateHandle.get("count") ?: "0"
println(count)

medium

A. println() cannot print variables

B. Missing key in get() method

C. SavedStateHandle cannot store Int values

D. Type mismatch: trying to assign Int to String without conversion

Solution

1. Step 1: Check variable types

   The value stored is Int (10), but retrieved as String without conversion.

2. Step 2: Understand Kotlin type safety

   Assigning Int to String variable causes a type mismatch error.

3. Final Answer:

   Type mismatch: trying to assign Int to String without conversion -> Option D

4. Quick Check:

   Type mismatch error = D [OK]

Hint: Match types when getting values from SavedStateHandle [OK]

Common Mistakes:

• Ignoring type mismatch errors
• Assuming automatic type conversion
• Thinking SavedStateHandle only stores strings

5.

You want to save a user's score in SavedStateHandle and restore it after a configuration change. Which approach correctly ensures the score is saved and retrieved safely?

class ScoreViewModel(private val savedStateHandle: SavedStateHandle) : ViewModel() {
    fun saveScore(score: Int) {
        // What to do here?
    }
    fun getScore(): Int {
        // What to do here?
    }
}

hard

A. saveScore: savedStateHandle.set("score", score)
getScore: savedStateHandle.get<Int>("score") ?: 0

B. saveScore: savedStateHandle.put("score", score)
getScore: savedStateHandle.get("score") as Int

C. saveScore: savedStateHandle.save("score", score)
getScore: savedStateHandle.get("score") ?: 0

D. saveScore: savedStateHandle.set("score", score.toString())
getScore: savedStateHandle.get<String>("score")?.toInt() ?: 0

Solution

1. Step 1: Use correct methods to save and get data

   Use set to save and get<Int> to retrieve with a default fallback.

2. Step 2: Validate type safety and default value

   saveScore: savedStateHandle.set("score", score) getScore: savedStateHandle.get<Int>("score") ?: 0 uses correct method names and safely returns 0 if no score is saved.

3. Final Answer:

   saveScore: savedStateHandle.set("score", score) getScore: savedStateHandle.get<Int>("score") ?: 0 -> Option A

4. Quick Check:

   Use set() and get<Int>() with default = B [OK]

Hint: Always use set() and get<Type>() with default fallback [OK]

Common Mistakes:

• Using non-existent methods like put() or save()
• Storing Int as String unnecessarily
• Not providing default value on get()