Passing data between activities in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an Intent to start SecondActivity.

Android Kotlin

val intent = Intent(this, [1]::class.java)
startActivity(intent)

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

ASecondActivity

BMainActivity

CAppCompatActivity

DIntent

Attempts:

3 left

💡 Hint

Common Mistakes

Using the current activity class instead of the target activity.

Forgetting to add ::class.java after the activity name.

You create an Intent specifying the current context and the target activity class. Here, SecondActivity is the destination.

2fill in blank

medium

Complete the code to put a string extra named "username" into the Intent.

Android Kotlin

intent.putExtra("username", [1])

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

A"userName"

Busername

CuserName

Duser_name

Attempts:

3 left

💡 Hint

Common Mistakes

Putting quotes around the variable name, which sends the literal text instead of the variable's value.

Using the key name instead of the variable.

The second argument to putExtra is the variable holding the string value you want to send. Here, userName is the variable.

3fill in blank

hard

Fix the error in retrieving the string extra named "username" from the Intent.

Android Kotlin

val user = intent.[1]("username")

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AgetExtra

BgetExtraString

CgetString

DgetStringExtra

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method that does not exist like getExtraString.

Using getString which is not a method of Intent.

To get a string extra from an Intent, use getStringExtra with the key name.

4fill in blank

hard

Fill both blanks to safely retrieve an integer extra named "age" with a default value of 0.

Android Kotlin

val age = intent.[1]("age", [2])

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AgetIntExtra

BgetExtraInt

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong method name like getExtraInt.

Forgetting to provide a default value.

Use getIntExtra with the key and a default value to safely get an integer extra.

5fill in blank

hard

Fill all three blanks to create an Intent, put a boolean extra "isAdmin", and start the activity.

Android Kotlin

val intent = Intent(this, [1]::class.java)
intent.[2]("isAdmin", [3])
startActivity(intent)

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

AAdminActivity

BputExtra

Ctrue

DMainActivity

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong activity class.

Using a wrong method name instead of putExtra.

Passing the string "true" instead of the boolean true.

Create an Intent for AdminActivity, add a boolean extra with putExtra, and start the activity.

Practice

1. What is the primary method to send data from one activity to another in Android Kotlin?

easy

A. Use an Intent with putExtra() to attach data.

B. Use a global variable to share data.

C. Call the other activity's method directly.

D. Use a database to pass data instantly.

Solution

1. Step 1: Understand Intent usage

   Intent is the standard way to start a new activity and can carry data with putExtra().

2. Step 2: Recognize data passing method

   putExtra() attaches key-value pairs to the Intent for the next activity to retrieve.

3. Final Answer:

   Use an Intent with putExtra() to attach data. -> Option A

4. Quick Check:

   Intent + putExtra() = Data passing [OK]

Hint: Remember: Intent carries data with putExtra() [OK]

Common Mistakes:

• Trying to call methods of another activity directly
• Using global variables which is not recommended
• Assuming database is needed for simple data passing

2. Which of the following is the correct syntax to add a String extra named "username" to an Intent in Kotlin?

easy

A. intent.setExtra("username", username)

B. intent.addExtra("username" to username)

C. intent.putExtra("username", username)

D. intent.putData("username", username)

Solution

1. Step 1: Recall Intent method for extras

   putExtra() is the correct method to add data to an Intent.

2. Step 2: Check syntax correctness

   putExtra() takes a key and a value as parameters, matching intent.putExtra("username", username).

3. Final Answer:

   intent.putExtra("username", username) -> Option C

4. Quick Check:

   putExtra() syntax correct = intent.putExtra("username", username) [OK]

Hint: Use putExtra(key, value) to add data to Intent [OK]

Common Mistakes:

• Using non-existent methods like addExtra or setExtra
• Confusing putExtra with putData
• Missing quotes around the key string

3. Given this code in Activity A:

val intent = Intent(this, ActivityB::class.java)
intent.putExtra("age", 25)
startActivity(intent)

What code correctly retrieves the "age" integer in Activity B?

medium

A. val age = intent.getIntExtra("age", 0)

B. val age = intent.getStringExtra("age")

C. val age = intent.getExtra("age") as Int

D. val age = intent.getInt("age")

Solution

1. Step 1: Identify the data type sent

   The value sent is an integer 25, so we must retrieve it as an Int.

2. Step 2: Use correct retrieval method

   getIntExtra() retrieves an Int extra with a default fallback value.

3. Final Answer:

   val age = intent.getIntExtra("age", 0) -> Option A

4. Quick Check:

   Integer extra retrieval = getIntExtra() [OK]

Hint: Use get<Type>Extra(key, default) matching sent data type [OK]

Common Mistakes:

• Using getStringExtra() for an integer value
• Trying to cast getExtra() without safe methods
• Using non-existent getInt() method

4. What is wrong with this code snippet in Activity B for retrieving a String extra named "email"?

val email = intent.getStringExtra("email")!!

medium

A. getStringExtra() does not exist for Intent.

B. Using !! can cause a crash if "email" extra is missing.

C. The key "email" should be an integer resource ID.

D. Intent extras cannot hold String values.

Solution

1. Step 1: Understand !! operator risk

   Using !! forces a non-null value and crashes if the extra is missing (null).

2. Step 2: Recognize safe retrieval practice

   It's safer to check for null or provide a default instead of forcing !!.

3. Final Answer:

   Using !! can cause a crash if "email" extra is missing. -> Option B

4. Quick Check:

   Unsafe !! usage risks crash [OK]

Hint: Avoid !! on extras; check for null safely [OK]

Common Mistakes:

• Assuming extras always exist without null checks
• Thinking getStringExtra() is invalid
• Confusing keys with resource IDs

5. You want to pass a list of user IDs (List<Int>) from Activity A to Activity B. Which approach correctly sends and retrieves this list?

hard

A. Store the list in a static variable and access it directly in Activity B

B. Use intent.putExtra("userIds", userIds) and retrieve with getIntExtra("userIds", 0)

C. Serialize the list to JSON string and send with putExtra("userIds", jsonString), then parse in Activity B

D. Use intent.putIntegerArrayListExtra("userIds", ArrayList(userIds)) and retrieve with getIntegerArrayListExtra("userIds")

Solution

1. Step 1: Identify correct method for List<Int>

   Intent supports ArrayList<Int> via putIntegerArrayListExtra() and getIntegerArrayListExtra().

2. Step 2: Confirm retrieval matches sending method

   Using these methods ensures type safety and proper data transfer.

3. Final Answer:

   Use intent.putIntegerArrayListExtra("userIds", ArrayList(userIds)) and retrieve with getIntegerArrayListExtra("userIds") -> Option D

4. Quick Check:

   Use put/getIntegerArrayListExtra for List<Int> [OK]

Hint: Use put/getIntegerArrayListExtra for List<Int> [OK]

Common Mistakes:

• Trying to send List<Int> directly with putExtra()
• Using getIntExtra() for a list
• Using static variables which breaks encapsulation