Navigating between composables in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to navigate to the "Profile" screen when the button is clicked.

Android Kotlin

Button(onClick = { navController.[1]("profile") }) {
    Text("Go to Profile")
}

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

Alaunch

Bnavigate

Cstart

DpopBackStack

Attempts:

3 left

💡 Hint

Common Mistakes

Using popBackStack() which goes back instead of forward.

Using start() which is not a NavController function.

The navigate() function is used to move to another composable screen by specifying its route.

2fill in blank

medium

Complete the code to define a NavHost with a start destination of "home".

Android Kotlin

NavHost(navController = navController, startDestination = "[1]") {
    composable("home") { HomeScreen() }
    composable("profile") { ProfileScreen() }
}

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

Ahome

Bprofile

Cdashboard

Dmain

Attempts:

3 left

💡 Hint

Common Mistakes

Setting startDestination to a route not defined in NavHost.

Using a route name that does not match any composable.

The startDestination should be set to "home" to show the HomeScreen first.

3fill in blank

hard

Fix the error in the code to pop back to the previous screen correctly.

Android Kotlin

navController.[1]()

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

Aback

BnavigateBack

CgoBack

DpopBackStack

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent functions like navigateBack or goBack.

Trying to use back() which is not a NavController method.

popBackStack() is the correct function to go back to the previous composable screen.

4fill in blank

hard

Fill both blanks to navigate to "details" screen with an argument "itemId".

Android Kotlin

navController.navigate("details/$[1]") {
    launchSingleTop = [2]
}

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

AitemId

Btrue

Cfalse

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong argument name in the route string.

Setting launchSingleTop to false causing multiple instances.

The route needs the argument name 'itemId' and launchSingleTop should be true to avoid multiple copies.

5fill in blank

hard

Fill all three blanks to define a composable with a route that accepts a "userId" argument of type String.

Android Kotlin

composable(route = "user/[1]", arguments = listOf(navArgument("[2]") {
    type = [3]
})) {
    UserScreen()
}

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

AuserId

CNavType.StringType

DNavType.IntType

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for route and argument.

Using NavType.IntType for a string argument.

The route and argument name must match 'userId' and the argument type is NavType.StringType for strings.

Practice

1. What is the main purpose of NavController in Jetpack Compose navigation?

easy

A. To create UI elements inside a composable

B. To handle database operations

C. To manage navigation between composable screens

D. To style composables with themes

Solution

1. Step 1: Understand the role of NavController

   NavController is responsible for controlling navigation actions between composables in an app.

2. Step 2: Differentiate from other components

   It does not create UI elements, handle databases, or style components; those are handled by other parts of Compose or Android.

3. Final Answer:

   To manage navigation between composable screens -> Option C

4. Quick Check:

   NavController manages navigation [OK]

Hint: NavController controls screen changes in Compose [OK]

Common Mistakes:

• Confusing NavController with UI creation
• Thinking NavController handles data or styling
• Mixing NavController with ViewModel

2. Which of the following is the correct syntax to navigate to a composable with route "profile" using NavController named navController?

easy

A. navController.navigate("profile")

B. navController.goTo("profile")

C. navController.move("profile")

D. navController.open("profile")

Solution

1. Step 1: Recall the navigation method

   The correct method to navigate is navigate() on NavController.

2. Step 2: Check method names

   Only navigate() is valid; others like goTo(), move(), or open() do not exist.

3. Final Answer:

   navController.navigate("profile") -> Option A

4. Quick Check:

   Use navigate() to change screens [OK]

Hint: Use navigate() method on NavController [OK]

Common Mistakes:

• Using non-existent methods like goTo or move
• Forgetting to pass route as a string
• Calling navigation on wrong object

3. Given this code snippet inside a composable:

val navController = rememberNavController()
Button(onClick = { navController.navigate("details") }) {
  Text("Go to Details")
}

What happens when the button is clicked?

medium

A. The app navigates to the composable with route "details"

B. The app closes immediately

C. Nothing happens because navigate() is incorrect

D. The app crashes due to missing NavHost

Solution

1. Step 1: Understand the button's onClick action

   The button calls navController.navigate("details") which triggers navigation to the "details" route.

2. Step 2: Consider NavHost presence

   Assuming NavHost is set up correctly with "details" route, navigation will succeed and show that screen.

3. Final Answer:

   The app navigates to the composable with route "details" -> Option A

4. Quick Check:

   Button triggers navigate() to details [OK]

Hint: Button click calls navigate() to change screen [OK]

Common Mistakes:

• Assuming navigate() does nothing
• Confusing navigation with app closing
• Ignoring NavHost setup requirement

4. Consider this code snippet:

navController.navigate("home")
navController.popBackStack()

What is the likely problem here?

medium

A. popBackStack() is not a valid NavController method

B. Calling popBackStack() immediately after navigate() may prevent navigation

C. navigate() requires a NavHost to be null

D. No problem; this code navigates then goes back correctly

Solution

1. Step 1: Analyze the sequence of calls

   Calling navigate("home") pushes a new screen, but immediately calling popBackStack() removes the top screen.

2. Step 2: Understand effect on navigation

   This means the navigation to "home" is undone immediately, so user may not see the new screen.

3. Final Answer:

   Calling popBackStack() immediately after navigate() may prevent navigation -> Option B

4. Quick Check:

   popBackStack() right after navigate() cancels navigation [OK]

Hint: Don't popBackStack() right after navigate() [OK]

Common Mistakes:

• Thinking popBackStack() is invalid
• Assuming navigation always succeeds despite popBackStack()
• Ignoring call order effects

5. You want to navigate from a composable "list" to "details/{itemId}" passing an item ID as argument. Which code correctly navigates to details screen with itemId = 42?

hard

A. navController.navigate("details/{itemId}")

B. navController.navigate("details")

C. navController.navigate("details?itemId=42")

D. navController.navigate("details/42")

Solution

1. Step 1: Understand route parameter usage

   When route has a placeholder like "details/{itemId}", you replace {itemId} with actual value in the route string.

2. Step 2: Check each option

   navController.navigate("details/42") correctly replaces {itemId} with 42. navController.navigate("details") misses the parameter. navController.navigate("details?itemId=42") uses query syntax which is not standard here. navController.navigate("details/{itemId}") uses the placeholder literally, which won't work.

3. Final Answer:

   navController.navigate("details/42") -> Option D

4. Quick Check:

   Replace {itemId} with actual value in route [OK]

Hint: Replace placeholders with actual values in route string [OK]

Common Mistakes:

• Passing route with placeholder instead of value
• Using query parameters incorrectly
• Omitting required route arguments