What is the purpose of using Android ViewModel?

The Android ViewModel is a design pattern that separates data from UI, leading to more efficient data management and improved user experience. It is primarily used to manage data related to the UI, and retains data during device configuration changes such as screen rotation.

Some benefits of using ViewModel include:

1. Lifecycle-aware: The ViewModel is associated with the lifecycle of an Activity or Fragment, which means the ViewModel can retain data during configuration changes without losing state.
2. Data sharing: Multiple components (such as Activity and Fragment) can share the same instance of a ViewModel, allowing data to be shared between different components.
3. Separation of concerns: The ViewModel is responsible for handling UI-related data, completely separating business logic from UI.

The steps to use ViewModel are as follows:

1. Create a class that inherits from ViewModel, which will include the data you want to retain in the UI.
2. In Activity or Fragment, you can use the methods provided by ViewModelProvider to obtain an instance of ViewModel.
3. Observe the data in the ViewModel within the UI in order to update the UI when the data changes.
4. Update data in the ViewModel and ensure that the setValue() or postValue() method of LiveData is called at the appropriate time to notify observers.

In short, the main purpose of ViewModel is to serve as a container for managing UI-related data and ensuring that data is not lost when the device configuration changes.