Helper functions to manually create your own SavedStateHandle with ease.

SavedStateHandle.kt

fun ComponentActivity.lazySavedStateHandle(
        key: String = this::class.java.canonicalName,
        defaultState: Bundle? = intent?.extras,
): Lazy<SavedStateHandle> = lazy(LazyThreadSafetyMode.NONE) {
    SavedStateHandle(savedStateRegistry, key, defaultState)
}

fun Fragment.lazySavedStateHandle(
        key: String = this::class.java.canonicalName,
        defaultState: Bundle? = arguments,
): Lazy<SavedStateHandle> = lazy(LazyThreadSafetyMode.NONE) {
    SavedStateHandle(savedStateRegistry, key, defaultState)
}

private fun SavedStateHandle(
        savedStateRegistry: SavedStateRegistry,
        key: String,
        defaultState: Bundle?,
): SavedStateHandle {
    val restoredState = savedStateRegistry.consumeRestoredStateForKey(key)
    val handle = SavedStateHandle.createHandle(restoredState, defaultState)
    savedStateRegistry.registerSavedStateProvider(key, handle.savedStateProvider())
    return handle
}