How to Implement ViewModel Inside a Fragment in Android

Learn how to effectively implement a `ViewModel` in an Android Fragment using Kotlin, avoiding common errors and utilizing best practices.
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This video is based on the question https://stackoverflow.com/q/70332686/ asked by the user 'Kafabih' ( https://stackoverflow.com/u/16660702/ ) and on the answer https://stackoverflow.com/a/70332812/ provided by the user 'AmrDeveloper' ( https://stackoverflow.com/u/7227834/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Implement ViewModel Inside a Fragment in Android

When working with Android development, you might encounter issues while trying to implement a ViewModel within a Fragment. If you've tried using a ViewModel but ended up with runtime exceptions, you're not alone. Let's dive into how to properly set up your fragment with a ViewModel, avoiding common pitfalls along the way.

The Problem

You might have attempted to link a ViewModel to your fragment like this:

[[See Video to Reveal this Text or Code Snippet]]

However, you might see an error such as:

[[See Video to Reveal this Text or Code Snippet]]

This error often arises due to improper initialization of the ViewModel. But fear not; we can easily remedy this with a few best practices in mind.

The Solution

1. Use Fragment Extension

One effective way to implement your ViewModel in a fragment is to utilize the Fragment KTX Extension. This library provides a more concise way to access ViewModel instances. To get started with this approach, ensure you have the appropriate dependency in your Gradle file.

Add Dependency

Make sure to include the following line in your build.gradle (Module) file:

[[See Video to Reveal this Text or Code Snippet]]

2. Defining your ViewModel

Next, when you want to define your ViewModel, use the viewModels delegate for a fragment scoped ViewModel or activityViewModels delegate for an activity-shared ViewModel. Here’s how:

Fragment ViewModel

For a ViewModel specific to the fragment:

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Activity Shared ViewModel

For sharing a ViewModel between fragments within the same activity:

[[See Video to Reveal this Text or Code Snippet]]

3. Complete Fragment Implementation

Here's an example of how your complete Fragment class might look using the ViewModelProvider correctly:

[[See Video to Reveal this Text or Code Snippet]]

Key Takeaways

Always ensure you are importing the necessary KTX libraries for better integration of ViewModel with Fragments.

Use viewModels() for Fragment-specific ViewModels.

Utilize activityViewModels() when you want to share your ViewModel across multiple fragments.

By following these guidelines, you can smoothly implement ViewModel within your Android fragments, reducing the chances of runtime errors while enhancing the robustness of your applications.

In conclusion, adopting these practices will ensure a smoother experience as you develop your Android applications using Kotlin. Embrace the power of architecture components to create more maintainable and user-friendly applications!

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