How to pass data between Fragments with Jetpack Navigation?

What's really being asked

This question tests your knowledge of the modern, recommended pattern for passing data between destinations in Android. The key is demonstrating an understanding of type safety and compile-time checks, which are the primary benefits of using the Safe Args Gradle plugin over older, manual methods. It separates candidates who know the modern Jetpack way from those still using error-prone manual Bundle manipulation.

The full answer

A strong answer walks through four distinct steps in order. First, you define the argument in the navigation graph XML file by adding an <argument> tag to the destination fragment, specifying its name and argType. Second, you enable the Safe Args Gradle plugin in your build.gradle files, which triggers code generation. Third, in the source fragment, you use the auto-generated Directions class to create a type-safe action, passing the data as a parameter (e.g., HomeFragmentDirections.actionHomeToProfile(userId)). This returns a NavDirections object that you pass to navController.navigate(). Fourth, in the destination fragment, you retrieve the data using the generated Args class, typically with the 'by navArgs()' Kotlin property delegate.

The mistakes people make

The most common wrong answer is describing how to manually create a Bundle, put data into it with a string key, and pass that Bundle to the navigate() function. While this works, it's the old, error-prone method that Safe Args is designed to replace. It signals a lack of familiarity with modern Android development practices. Another red flag is suggesting a shared ViewModel for this simple use case. While ViewModels are great for sharing complex, observable state across a flow, they are overkill for simple, one-way argument passing and indicate a misapplication of architectural patterns.

What usually comes next

Expect follow-up questions like: "When would you use a shared ViewModel instead of navigation arguments?" (Answer: For complex data, two-way data flow, or state that needs to be shared by multiple destinations in a flow). Another is "How do you pass a custom Parcelable object?" (Answer: You set the app:argType to the fully qualified class name of your Parcelable object). Finally, "What are the benefits of Safe Args?" (Answer: Type safety, null safety, and compile-time checks, which eliminate a class of runtime crashes).

A concrete example

To pass a userId string from HomeFragment to ProfileFragment: In your nav_graph.xml, add <argument android:name="userId" app:argType="string" /> inside the ProfileFragment destination. In HomeFragment, you'd call val action = HomeFragmentDirections.actionHomeFragmentToProfileFragment(userId = "user-123") and then findNavController().navigate(action). In ProfileFragment, you'd retrieve it with val args: ProfileFragmentArgs by navArgs() and then use args.userId to get the "user-123" value.