Android ViewModel is a crucial component in the MVVM (Model-View-ViewModel) architecture, designed to help manage and persist UI-related data in a lifecycle-conscious way. It acts as a communication center between the Repository (data) and the UI. In this comprehensive guide, we will delve into the ins and outs of Android ViewModel, its benefits, and how to effectively use it in your Android applications.

Benefits of Android ViewModel:

1. Lifecycle Awareness: ViewModel is lifecycle-aware, which means it is designed to survive configuration changes such as screen rotations. This ensures that the data is not lost when the UI is recreated.

2. Separation of Concerns: ViewModel separates the UI-related data from the UI controller, making the code more maintainable and testable.

3. Improved Testability: Since the business logic is shifted to the ViewModel, it becomes easier to write unit tests for the View and ViewModel separately.

How to Use Android ViewModel:

To implement Android ViewModel in your project, you need to include the 'androidx.lifecycle:viewmodel' dependency in your app's build.gradle file. Then, create a ViewModel class that extends the 'ViewModel' class provided by the Android Architecture Components. The ViewModel class should contain the data required for the UI and the business logic to operate on that data.

Example:

```java

public class MyViewModel extends ViewModel {

private MutableLiveData data = new MutableLiveData<>();

public void setData(String newData) {

data.setValue(newData);

}

public LiveData getData() {

return data;

}

}

```

Once the ViewModel is created, you can observe the data changes using LiveData in your UI components (e.g., Activity or Fragment) and update the UI accordingly.

Best Practices for Android ViewModel:

1. Avoid Holding Context: It's important to avoid holding a reference to the Context object in the ViewModel to prevent memory leaks.

2. Keep it Lightweight: ViewModel should not contain heavy computation or long-running operations. It should focus on managing and providing data to the UI.

3. Use ViewModel Factory: When the ViewModel requires parameters for initialization, it's recommended to use ViewModel Factory to create instances of the ViewModel.

In conclusion, Android ViewModel is a powerful tool for managing and retaining UI-related data in an Android application. By leveraging the benefits of ViewModel and following best practices, developers can create more resilient and maintainable Android apps. If you're looking to build robust and efficient Android applications, mastering Android ViewModel is a must-have skill.