SavedStateHandle in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to retrieve a value from SavedStateHandle.

Android Kotlin

val name: String? = savedStateHandle.get<String>([1])

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

A"userName"

BuserName

C"user_name"

Duser_name

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the key string.

Using a variable name without quotes.

The key for SavedStateHandle must be a string literal, so it needs quotes.

2fill in blank

medium

Complete the code to save a value into SavedStateHandle.

Android Kotlin

savedStateHandle.set([1], "John")

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

Auser_name

BuserName

C"user_name"

D"userName"

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted keys when calling set().

Confusing variable names with string keys.

The key must be a string literal with quotes when saving a value.

3fill in blank

hard

Fix the error in the code to observe a LiveData from SavedStateHandle.

Android Kotlin

val liveData = savedStateHandle.getLiveData<String>([1])

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

Auser_name

B"userName"

CuserName

D"user_name"

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted keys causing compile errors.

Mixing variable names with string keys.

The key must be a string literal with quotes to correctly observe LiveData.

4fill in blank

hard

Fill both blanks to create a SavedStateHandle with initial values.

Android Kotlin

val initialState = mapOf([1] to "Alice", [2] to 25)
initialState.forEach { (k, v) -> savedStateHandle.set(k, v) }

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

A"name"

B"age"

Cname

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted keys in the map.

Using variable names instead of string keys.

Keys in maps and SavedStateHandle must be string literals with quotes.

5fill in blank

hard

Fill all three blanks to update and retrieve a value safely from SavedStateHandle.

Android Kotlin

savedStateHandle.set([1], 100)
val score: Int = savedStateHandle.get<Int>([2]) ?: [3]

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

A"score"

C0

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using different keys for set and get.

Not providing a default value causing null errors.

Using unquoted keys.

Use the same quoted key for set and get, and provide a default value if null.

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()