postValue

postValue is a method of MutableLiveData in Android's Architecture Components (Jetpack). It posts a value to be set on the main thread, enabling thread-safe updates to LiveData from background threads. postValue can be called from any thread, including workers or asynchronous callbacks. When invoked, MutableLiveData schedules the update to be delivered on the main thread's message queue. If multiple postValue calls occur before the main thread handles the posted task, only the last value is delivered to observers.

By contrast, setValue must be called on the main thread and updates the value immediately, notifying observers synchronously on the main thread. Observers registered to LiveData receive updates according to their lifecycle state and are notified on the main thread.

If no observers are active at the moment of a postValue, the value is still stored and delivered to observers when they become active. This behavior makes postValue suitable for updating UI-related data from background work without directly touching the UI thread.

Typical usage involves performing background operations (such as network requests or database queries) and calling postValue with the result to trigger UI updates in a lifecycle-aware and thread-safe manner. postValue thus complements setValue by providing a safe way to publish changes from non-UI threads.