ViewModelProviders is deprecated in 110

For Android developers entrenched in the lifecycle-aware architecture components, encountering the deprecation of ViewModelProviders in version 1.1.0 likely caused a ripple of concern. This class, a cornerstone for retrieving and managing ViewModel instances, suddenly presented a warning, signaling a necessary shift in approach. Understanding the reasons behind this change, and more importantly, how to adapt your code to the modern alternatives, is crucial for maintaining a robust and future-proof Android application. This article delves into the specifics of the ViewModelProviders deprecation, explores the recommended replacement mechanisms, and provides practical examples to guide you through the transition. Embrace the evolution – let’s navigate the modern Android development landscape together.

Understanding the Deprecation of ViewModelProviders

The deprecation of ViewModelProviders in Android Architecture Components 1.1.0 marked a significant step towards a more streamlined and type-safe way of managing ViewModel instances. Previously, ViewModelProviders served as a central access point, allowing developers to retrieve ViewModel instances associated with an Activity or Fragment. However, this approach relied heavily on string-based keys and reflection, which introduced potential runtime errors and reduced type safety. It also made dependency injection more complex, as the framework lacked a clear way to inject custom ViewModel factories.

The decision to deprecate ViewModelProviders stemmed from Google’s commitment to improving the overall developer experience and ensuring code maintainability. By moving away from the older approach, they aimed to provide a more robust and predictable mechanism for ViewModel creation and management. This shift aligns with modern Android development practices, emphasizing the use of dependency injection frameworks like Hilt or Dagger to manage dependencies and improve testability. The deprecation doesn’t mean your existing code will suddenly break, but it’s a clear signal that migrating to the recommended alternatives is essential for long-term project health.

Think of it this way: ViewModelProviders was like a general store where you could ask for any item (ViewModel) by name. The storekeeper (the framework) would try to find it for you, but sometimes it might not exist or be the wrong type. The new approach is like having specialized shops (ViewModelProvider.Factory implementations) that guarantee you’ll get the correct item and that the storekeeper knows exactly how to create it if it doesn’t already exist. This increased specificity reduces ambiguity and the potential for errors.

The Recommended Replacement: ViewModelProvider.Factory

The primary replacement for ViewModelProviders is the ViewModelProvider.Factory interface. This interface provides a standardized way to create ViewModel instances, allowing you to inject dependencies directly into the ViewModel constructor. By implementing a custom ViewModelProvider.Factory, you gain complete control over the ViewModel creation process, ensuring that all necessary dependencies are available and properly initialized. This approach eliminates the reliance on reflection and string-based keys, resulting in more robust and type-safe code.

Implementing a custom ViewModelProvider.Factory typically involves creating a class that implements the interface and overrides the create() method. Within the create() method, you can instantiate your ViewModel, passing in any required dependencies. These dependencies can be obtained from a dependency injection framework like Hilt or Dagger, or manually injected if your project doesn’t use dependency injection. The key benefit is that the ViewModel is created with all its dependencies satisfied, leading to cleaner and more maintainable code. For instance, if your ViewModel requires a repository for data access, the Factory is where you’d inject that repository instance.

Let’s consider an example where your MyViewModel depends on a UserRepository. Instead of relying on ViewModelProviders, you would create a MyViewModelFactory that takes a UserRepository as a constructor parameter. The create() method would then instantiate MyViewModel, passing in the UserRepository instance. This ensures that MyViewModel always has access to the required data layer, improving the overall reliability and testability of your application. This is a huge step up in dependency management. This can be further simplified using DI frameworks like Hilt. Learn more about dependency injection here.

Implementing ViewModelProvider.Factory: A Practical Guide

Migrating from ViewModelProviders to ViewModelProvider.Factory involves a few key steps. First, you need to identify the dependencies required by your ViewModel. Second, you need to create a custom ViewModelProvider.Factory implementation that handles the creation of your ViewModel and injects the necessary dependencies. Finally, you need to update your Activity or Fragment to use the custom ViewModelProvider.Factory when retrieving the ViewModel instance.

Here’s a step-by-step guide to implementing ViewModelProvider.Factory:

1. Identify the dependencies required by your ViewModel.
2. Create a custom ViewModelProvider.Factory implementation.
3. Override the create() method in your factory.
4. Instantiate your ViewModel within the create() method, passing in the required dependencies.
5. Use the custom ViewModelProvider.Factory in your Activity or Fragment.

To illustrate this process, let’s say you have a ProfileViewModel that needs a ProfileRepository and a SharedPreferences instance. Your ProfileViewModelFactory would look something like this:

java class ProfileViewModelFactory( private val profileRepository: ProfileRepository, private val sharedPreferences: SharedPreferences ) : ViewModelProvider.Factory { override fun create(modelClass: Class): T { if (modelClass.isAssignableFrom(ProfileViewModel::class.java)) { return ProfileViewModel(profileRepository, sharedPreferences) as T } throw IllegalArgumentException(“Unknown ViewModel class”) } } Then, in your Activity or Fragment, you would retrieve the ViewModel using the factory:

java val factory = ProfileViewModelFactory(profileRepository, sharedPreferences) profileViewModel = ViewModelProvider(this, factory).get(ProfileViewModel::class.java) This approach ensures that the ProfileViewModel is always created with the correct dependencies, making your code more reliable and easier to test. This method provides a clear and concise way to manage ViewModel dependencies.

Benefits of Using ViewModelProvider.Factory

The transition to ViewModelProvider.Factory offers several significant benefits over the deprecated ViewModelProviders approach. These benefits include improved type safety, enhanced dependency injection capabilities, and increased testability. By embracing ViewModelProvider.Factory, you can build more robust and maintainable Android applications.

Here’s a summary of the key advantages:

• Improved Type Safety: Eliminates reliance on string-based keys and reflection, reducing the risk of runtime errors.
• Enhanced Dependency Injection: Allows you to inject dependencies directly into the ViewModel constructor, simplifying dependency management.
• Increased Testability: Makes it easier to mock dependencies and write unit tests for your ViewModel.

Furthermore, using ViewModelProvider.Factory aligns with modern Android development practices and promotes a more modular and maintainable codebase. According to Google’s official documentation [^1^], “Using a custom factory allows you to pass dependencies into your ViewModel, making it easier to test and reuse.” This is a critical aspect of building scalable and reliable applications. The new factory approach offers a more structured and predictable way to create and manage ViewModels, which contributes to a better overall development experience. This also increases the long-term maintainability of your projects.

Featured Snippet: ViewModelProvider.Factory is the recommended replacement for the deprecated ViewModelProviders in Android. It provides a type-safe and dependency-injection-friendly way to create ViewModel instances. By implementing a custom factory, you gain control over the ViewModel creation process and can inject necessary dependencies directly into the ViewModel constructor, improving testability and maintainability.

FAQ: Addressing Common Questions about ViewModelProviders Deprecation

**Q: What happens if I continue to use ViewModelProviders?**

A: Your code will still work, but you'll receive a deprecation warning. It's highly recommended to migrate to `ViewModelProvider.Factory` to avoid potential issues in future Android versions and to take advantage of the benefits it offers.

**Q: Can I use ViewModelProvider.Factory without dependency injection frameworks like Hilt or Dagger?**

A: Yes, you can manually inject dependencies into your custom `ViewModelProvider.Factory`. However, using a dependency injection framework can simplify the process and improve code organization.

**Q: Is there a simple migration path from ViewModelProviders to ViewModelProvider.Factory?**

A: The migration involves creating a custom factory for each of your ViewModels. While it requires some initial effort, the long-term benefits of improved type safety and dependency management make it worthwhile.

**Q: Where can I find more examples of ViewModelProvider.Factory implementations?**

A: The Android Sunflower sample app \[^2^\] on GitHub provides a comprehensive example of using `ViewModelProvider.Factory` with Hilt. You can also find numerous tutorials and articles online that demonstrate different implementation approaches.

The deprecation of `ViewModelProviders` signifies a move towards more robust and maintainable Android architectures. Embracing `ViewModelProvider.Factory` not only addresses the deprecation warning but also unlocks significant advantages in terms of type safety, dependency injection, and testability. By following the steps outlined in this article and exploring the provided resources, you can seamlessly transition your codebase and build more reliable and scalable Android applications. Remember to always refer to the official Android documentation \[^3^\] for the most up-to-date information.

The shift may seem daunting at first, but it ultimately leads to cleaner, more testable, and more maintainable code. Take the time to understand the principles behind ViewModelProvider.Factory and how it integrates with dependency injection. Experiment with different implementation approaches and find the one that best suits your project’s needs. By embracing this modern approach, you’ll be well-equipped to build high-quality Android applications that stand the test of time.

• Remember to test your implementation thoroughly.
• Consult the official Android documentation for best practices.

Now is the perfect time to audit your existing codebase and identify areas where you can migrate from ViewModelProviders to ViewModelProvider.Factory. Start with smaller, less critical components and gradually work your way up to more complex ones. Consider exploring advanced topics like assisted injection with Hilt for even greater control over dependency management. The future of Android development favors those who embrace these modern techniques, so take the leap and unlock the full potential of your applications.

[^1^]: Android ViewModel Overview

[^2^]: Android Sunflower Sample App

[^3^]: Android Developers

Question & Answer :
Looking at the Google docs for ViewModel, they show the below sample code on how to get a ViewModel:

val model = ViewModelProviders.of(this).get(MyViewModel::class.java) 

When using the latest dependency android.arch.lifecycle:extensions:1.1.1 there is no such class ViewModelProviders.

Going to the documentation for ViewModelProviders, I saw a comment saying:

This class was deprecated in API level 1.1.0. Use ViewModelProvider.AndroidViewModelFactory

The problem is, when trying to use ViewModelProvider.AndroidViewModelFactory, cannot find an equivalent of method to get the instance of the ViewModel.

What i tried doing:

ViewModelProvider.AndroidViewModelFactory.getInstance(application).create(PlayerViewHolder::class.java) 

Hence the name of the method create, I get a new instance of the ViewModel every-time I call it, which is not what I am after.

Any ideas what is the replacement of deprecated code above?

I use lifecycle-extensions 2.2.0 version:

implementation "androidx.lifecycle:lifecycle-extensions:2.2.0" 

It should work, using ViewModelProvider constructor.

// With ViewModelFactory val viewModel = ViewModelProvider(this, YourViewModelFactory).get(YourViewModel::class.java) //Without ViewModelFactory val viewModel = ViewModelProvider(this).get(YourViewModel::class.java) 

2020/5/15 Update

I found another elegant way to achieve this, Android KTX can help

implementation "androidx.fragment:fragment-ktx:1.2.4" val viewmodel: MYViewModel by viewModels() val viewmodel: MYViewModel by viewModels { myFactory } //With factory 

Ref: https://developer.android.com/reference/kotlin/androidx/fragment/app/package-summary#viewmodels

2020/06/25: corrected the case of the delegate