InvalidationTracker

Kotlin |Java

open class InvalidationTracker

kotlin.Any
↳	androidx.room.InvalidationTracker

InvalidationTracker keeps a list of tables modified by queries and notifies its callbacks about these tables.

Summary

Nested classes
abstract	`Observer` An observer that can listen for changes in the database.

Public methods
open Unit	`addObserver(@NonNull observer: InvalidationTracker.Observer)` Adds the given observer to the observers list and it will be notified if any table it observes changes.
open Unit	`refreshVersionsAsync()` Enqueues a task to refresh the list of updated tables.
open Unit	`removeObserver(@NonNull observer: InvalidationTracker.Observer)` Removes the observer from the observers list.

Public methods

addObserver

@WorkerThread open fun addObserver(@NonNull observer: InvalidationTracker.Observer): Unit

Adds the given observer to the observers list and it will be notified if any table it observes changes.

Database changes are pulled on another thread so in some race conditions, the observer might be invoked for changes that were done before it is added.

If the observer already exists, this is a no-op call.

If one of the tables in the Observer does not exist in the database, this method throws an IllegalArgumentException.

This method should be called on a background/worker thread as it performs database operations.

Parameters
`observer`	InvalidationTracker.Observer: The observer which listens the database for changes.

refreshVersionsAsync

open fun refreshVersionsAsync(): Unit

Enqueues a task to refresh the list of updated tables.

This method is automatically called when RoomDatabase#endTransaction() is called but if you have another connection to the database or directly use , you may need to call this manually.

removeObserver

@WorkerThread open fun removeObserver(@NonNull observer: InvalidationTracker.Observer): Unit

Removes the observer from the observers list.

This method should be called on a background/worker thread as it performs database operations.

Parameters
`observer`	InvalidationTracker.Observer: The observer to remove.