How is LiveData observed in an Activity?

LiveData is a lifecycle-aware data holder that allows UI components to observe changes in the underlying data without needing to worry about the lifecycle of those components. The correct method to observe LiveData in an Activity is through calling liveData.observe(this, Observer { ... }). This approach ensures that the observation is tied to the lifecycle of the Activity, and LiveData automatically manages updates when the Activity goes through its lifecycle events.

By using this method, when the LiveData's data changes, the observer will be notified if the Activity is in an active state, meaning it is in the foreground and not destroyed or paused. This mechanism prevents memory leaks and ensures that you are not trying to update the UI when it is no longer in a state to do so.

Other options do not properly align with the intended way to observe LiveData. For instance, directly accessing the LiveData variable does not provide any way to respond to changes in the data it holds. Similarly, simply implementing the Observer interface without using the observe method does not effectively associate the observer with the LiveData’s lifecycle management. Using a subscribe method is not part of LiveData's implementation; LiveData primarily uses the observe pattern for updates.