Activity concept in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a basic Activity class in Kotlin.

Android Kotlin

class MainActivity : [1]() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
  }
}

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

AFragment

BAppCompatActivity

CService

DViewModel

Attempts:

3 left

💡 Hint

Common Mistakes

Using Fragment or Service instead of AppCompatActivity.

Forgetting to extend any class.

The MainActivity class must extend AppCompatActivity to be a valid Activity.

2fill in blank

medium

Complete the code to set the layout resource for the Activity.

Android Kotlin

override fun onCreate(savedInstanceState: Bundle?) {
  super.onCreate(savedInstanceState)
  [1](R.layout.activity_main)
}

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

AsetContentView

BfindViewById

CsetLayout

Dinflate

Attempts:

3 left

💡 Hint

Common Mistakes

Using inflate or setLayout which are not Activity methods.

Calling findViewById instead of setting the layout.

The method setContentView sets the UI layout for the Activity.

3fill in blank

hard

Fix the error in the Activity lifecycle method override.

Android Kotlin

override fun onStart() {
  super.[1]()
  // Additional code here
}

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AonCreate

BonResume

ConStart

DonPause

Attempts:

3 left

💡 Hint

Common Mistakes

Calling super.onCreate() inside onStart.

Forgetting the super call entirely.

When overriding onStart, call super.onStart() to maintain lifecycle behavior.

4fill in blank

hard

Fill both blanks to start a new Activity from the current one.

Android Kotlin

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

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ASecondActivity

BstartActivity

CMainActivity

Dfinish

Attempts:

3 left

💡 Hint

Common Mistakes

Using finish() instead of startActivity().

Using the wrong Activity class in the Intent.

To start a new Activity, create an Intent with the target Activity class and call startActivity with it.

5fill in blank

hard

Fill all three blanks to pass data to another Activity using Intent extras.

Android Kotlin

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

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

ADetailActivity

BputExtra

CstartActivity

DgetExtra

Attempts:

3 left

💡 Hint

Common Mistakes

Using getExtra instead of putExtra.

Forgetting to call startActivity.

Passing wrong Activity class.

Use putExtra to add data to the Intent, then call startActivity to launch the target Activity.

Practice

1. What is the main role of an Activity in an Android app?

easy

A. It stores app data permanently.

B. It handles network requests only.

C. It manages background tasks without UI.

D. It represents a single screen with a user interface.

Solution

1. Step 1: Understand Activity purpose

   An Activity is designed to show a screen where users interact.

2. Step 2: Compare options

   Only It represents a single screen with a user interface. correctly describes an Activity as a UI screen.

3. Final Answer:

   It represents a single screen with a user interface. -> Option D

4. Quick Check:

   Activity = Screen UI [OK]

Hint: Remember: Activity = one screen in app [OK]

Common Mistakes:

• Confusing Activity with data storage
• Thinking Activity runs without UI
• Mixing Activity with background services

2. Which method is used to set up the UI when an Activity starts?

easy

A. onResume()

B. onStart()

C. onCreate()

D. onPause()

Solution

1. Step 1: Identify lifecycle methods

   onCreate() is called when the Activity is first created to set up UI.

2. Step 2: Eliminate other methods

   onStart() and onResume() happen later; onPause() is for pausing.

3. Final Answer:

   onCreate() -> Option C

4. Quick Check:

   UI setup = onCreate() [OK]

Hint: UI setup always starts in onCreate() [OK]

Common Mistakes:

• Choosing onStart() or onResume() for UI setup
• Confusing onPause() as setup method
• Not knowing Activity lifecycle order

3. What will happen when this Activity code runs?

class MainActivity : AppCompatActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
  }
}

medium

A. The screen shows the layout defined in activity_main.xml.

B. The app shows a blank screen.

C. Nothing happens because onCreate is empty.

D. The app crashes due to missing layout.

Solution

1. Step 1: Analyze onCreate method

   It calls super.onCreate and sets content view to activity_main layout.

2. Step 2: Understand setContentView effect

   This loads and displays the UI from activity_main.xml on screen.

3. Final Answer:

   The screen shows the layout defined in activity_main.xml. -> Option A

4. Quick Check:

   setContentView loads layout = screen shows layout [OK]

Hint: setContentView shows UI layout on screen [OK]

Common Mistakes:

• Assuming onCreate does nothing
• Thinking app crashes without error
• Confusing blank screen with missing layout

4. Identify the error in this Activity code:

class MainActivity : AppCompatActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    setContentView(R.layout.activity_main)
    super.onCreate(savedInstanceState)
  }
}

medium

A. setContentView called before super.onCreate()

B. No error, code is correct

C. Missing call to super.onCreate()

D. onCreate method should not be overridden

Solution

1. Step 1: Check order of calls in onCreate

   super.onCreate() must be called before setContentView to initialize Activity properly.

2. Step 2: Identify mistake

   Here, setContentView is called first, which is incorrect and can cause issues.

3. Final Answer:

   setContentView called before super.onCreate() -> Option A

4. Quick Check:

   super.onCreate() first, then setContentView [OK]

Hint: Always call super.onCreate() before setContentView [OK]

Common Mistakes:

• Calling setContentView before super.onCreate()
• Forgetting to override onCreate
• Not calling super.onCreate() at all

5. You want to start a new Activity called DetailActivity from MainActivity. Which code snippet correctly starts the new Activity?

hard

A. startActivity(DetailActivity::class.java)

B. val intent = Intent(this, DetailActivity::class.java)
startActivity(intent)

C. Intent intent = new Intent(DetailActivity)
startActivity(intent)

D. val intent = Intent(DetailActivity)
startActivity()

Solution

1. Step 1: Understand Intent creation

   Intent requires context (this) and target Activity class (DetailActivity::class.java).

2. Step 2: Check startActivity usage

   startActivity(intent) correctly starts the new Activity with the Intent.

3. Final Answer:

   val intent = Intent(this, DetailActivity::class.java) startActivity(intent) -> Option B

4. Quick Check:

   Intent(this, TargetClass) + startActivity(intent) [OK]

Hint: Use Intent(this, TargetActivity::class.java) to start Activity [OK]

Common Mistakes:

• Omitting context in Intent constructor
• Calling startActivity without Intent
• Using wrong syntax for Intent creation