api_livedata/com.tomtom.tools.android.api.livedata/DistinctMutableLiveData

DistinctMutableLiveData

class DistinctMutableLiveData<T> : MutableLiveData<T>

An implementation of MutableLiveData that only emits updates when the value actually changed, i.e. when newValue != oldValue. This differs from regular MutableLiveData because if you set its value to an equal same value, it still emits an update, causing observers to get a callback.

This is more suitable than the distinctUntilChanged transformation for the cases where the values are not necessarily going to be observed: distinctUntilChanged only changes value when observers are registered.

NB: This should only be used in situations where it's guaranteed to not lead to side-effects. The most common situation where this should not be used is for instances of T that are both mutable and have a custom Object.equals implementation. This could lead to situations where a set value is ignored but mutated afterwards, meaning the value shouldn't have been ignored after all. As a guideline, only use DistinctMutableLiveData for types that could also be used as a key in a Map.

Constructors

DistinctMutableLiveData

constructor()

constructor(value: T)

Inherited properties

observedValue

val <T> LiveData<T>.observedValue: T?

Same as LiveData.getValue, except this variant throws a IllegalStateException when the LiveData instance does not have an active observer.

valueUpToDate

val <T> LiveData<T>.valueUpToDate: T?

Same as LiveData.getValue with the exception that the returned value is up to date even when the LiveData instance does not have an observer.

Functions

setValue

open override fun setValue(newValue: T?)

Inherited functions

add

@MainThread

fun <E> MutableLiveData<List<E>>.add(element: E): Boolean

Adds the specified element to the end of this MutableLiveData. The observers are notified of the new value.

addAll

@MainThread

fun <E> MutableLiveData<List<E>>.addAll(elements: Iterable<E>): Boolean

Adds all of the elements of the specified collection to the end of this MutableLiveData. The observers are notified of the new value if the list was changed.

any

fun <E> LiveData<out Collection<E>?>.any(predicate: (E) -> Boolean): Boolean

asLiveData

fun <T> MutableLiveData<T>.asLiveData(): LiveData<T>

Convenience method to create non-mutable LiveData fields without duplicating the type.

check

fun <T> LiveData<T>.check(predicate: (T) -> Boolean): Boolean

clear

@MainThread

fun <E> MutableLiveData<List<E>>.clear()

Removes all elements from this MutableLiveData. The observers are notified of the new value if the list was changed.

@JvmName(name = "clearKV")

@MainThread

fun <K, V> MutableLiveData<Map<K, V>>.clear()

Removes all elements from a LiveData's Map, notifying observers of the new value.

contains

fun <E> LiveData<out Collection<E>?>.contains(element: E): Boolean

@MainThread

operator fun <K> LiveData<out Map<K, *>>.contains(key: K): Boolean

Returns true if the LiveData's value contains the specified key.

containsAll

fun <E> LiveData<out Collection<E>?>.containsAll(elements: Collection<E>): Boolean

containsKey

@MainThread

fun <K> LiveData<out Map<K, *>>.containsKey(key: K): Boolean

Returns true if the LiveData's value contains the specified key.

containsValue

@MainThread

fun <K, V> LiveData<out Map<K, V>>.containsValue(value: V): Boolean

Returns true if the LiveData's value maps one or more keys to the specified value.

find

@MainThread

fun <K, V> LiveData<out Map<K, V>>.find(predicate: (Map.Entry<K, V>) -> Boolean): Map.Entry<K, V>?

Finds the first entry from a LiveData's Map's value that matches the given predicate. Returns null if no entry is found or if the LiveData has no value.

flatMap

fun <T, S> LiveData<out Collection<S>>.flatMap(mapFunction: (S) -> LiveData<out Collection<T>>): LiveData<Collection<T>>

Transforms a LiveData containing a list of type T, which contains all the child elements from each element in this LiveData list by flattening it.

flatMapBySource

fun <T, S> LiveData<out Collection<S>>.flatMapBySource(mapFunction: (S) -> LiveData<out Collection<T>>): LiveData<Collection<Pair<S, T>>>

Transforms a LiveData containing a list of type T, which contains all the child elements from each element in this LiveData list together with its source, by flattening it.

forEach

@MainThread

fun <E> LiveData<out Iterable<E>?>.forEach(operation: (E) -> Unit)

Performs operation on each entry in a LiveData's collection. Does nothing if the LiveData has no value.

@MainThread

fun <K, V> LiveData<out Map<K, V>>.forEach(operation: (Map.Entry<K, V>) -> Unit)

Performs operation on each entry in a LiveData's Map. Does nothing if the LiveData has no value.

get

@MainThread

operator fun <K, V> LiveData<out Map<K, V>>.get(key: K): V?

Returns the value corresponding to the given key in the LiveData's value, or null if such a key is not present in the map or the LiveData has no value.

getOrDefault

@MainThread

fun <K, V> LiveData<out Map<K, V>>.getOrDefault(key: K, defaultValue: V): V

Returns the value corresponding to the given key in the LiveData's value, or defaultValue if such a key is not present in the map or the LiveData has no value.

getOrElse

@MainThread

fun <K, V> LiveData<out Map<K, V>>.getOrElse(key: K, defaultValue: () -> V): V

Returns the value for the given key in the LiveData's value, or the result of the defaultValue function if there was no entry for the given key or the LiveData has no value.

getOrPut

@MainThread

fun <K, V> MutableLiveData<Map<K, V>>.getOrPut(key: K, defaultValue: () -> V): V

Returns the value for the given key in the LiveData's value. If the key is not found, calls the defaultValue function, puts its result into the map under the given key and returns it. Creates a map if the LiveData has no value yet.

getValue

@Nullable

open fun getValue(): T?

hasActiveObservers

open fun hasActiveObservers(): Boolean

hasObservers

open fun hasObservers(): Boolean

ifTrue

fun <T, B : Boolean?> LiveData<B>.ifTrue(block: () -> LiveData<T>): LiveData<T?>

Executes and switchMaps to block if this has a true value. If this is false or null, it returns LiveData with value null. If this should not return null, ifTrueOrDefault can be used instead.

ifTrueOrDefault

fun <T : Any, B : Boolean?> LiveData<B>.ifTrueOrDefault(default: T, block: () -> LiveData<T>): LiveData<T>

Executes and switchMaps to block if this has a true value. If this is false or null, it returns LiveData with value default. This can be used instead of ifTrue when the default value should be something other than null. Note that this requires a non-null value for T in order for Kotlin's compiler to properly spot missing null-checks.

mapToValueOrUnset

@MainThread

fun <K, V> LiveData<Map<K, V>>.mapToValueOrUnset(key: K): LiveData<V>

Maps the value of the provided key, if that key exists in this map. Otherwise, no value is set. This is useful in cases where the map may not contain the requested entry but the resulting LiveData is not nullable as the client does not care about a null value. This removes the need for the client to have null checks in its code wherever the resulting LiveData is used.

merge

fun <T : Any, S : Any> LiveData<out Collection<S>>.merge(mapFunction: (S) -> LiveData<out T?>): LiveData<out Collection<T>>

Transforms LiveData containing a list that holds other LiveData instances into LiveData that contains the values from those LiveData instances. The returned LiveData will be updated when the source LiveData changes as well as when the internal LiveData instances change.

minusAssign

@MainThread

operator fun <E> MutableLiveData<List<E>>.minusAssign(element: E)

Removes a single instance of the specified element from a MutableLiveData, if it is present. The observers are notified of the new value if any of the specified elements was removed.

@MainThread

operator fun <E> MutableLiveData<List<E>>.minusAssign(elements: Iterable<E>)

Removes all elements from this MutableLiveData that are also contained in the given elements collection. The observers are notified of the new value if the list was changed.

@MainThread

operator fun <K, V> MutableLiveData<Map<K, V>>.minusAssign(key: K)

Removes the entry mapped by key from the LiveData's value, notifying observers of the new value.

none

fun <E> LiveData<out Collection<E>?>.none(predicate: (E) -> Boolean): Boolean

not

operator fun <T : Boolean?> LiveData<T>.not(): LiveData<T>

Negates the value of a boolean LiveData.

observe

@MainThread

open fun observe(@NonNull p0: LifecycleOwner, @NonNull p1: Observer<in T>)

observeForever

@MainThread

open fun observeForever(@NonNull p0: Observer<in T>)

observeNonNull

@MainThread

inline fun <T : Any> LiveData<T>.observeNonNull(owner: LifecycleOwner, crossinline onChanged: (T) -> Unit): Observer<T>

Adds the given onChanged lambda as an observer within the lifespan of the given owner and returns a reference to observer. The events are dispatched on the main thread.

observeOnce

@MainThread

inline fun <T> LiveData<T>.observeOnce(lifecycleOwner: LifecycleOwner, crossinline onChanged: (T) -> Unit): Observer<T>

Observes this LiveData for one change only and returns the one-time observer. The returned observer can be used to stop observing the LiveData when a callback is no longer desired. It is safe to remove the observer while it is executing or has been executed already.

observeWhile

@MainThread

inline fun <T> LiveData<T>.observeWhile(lifecycleOwner: LifecycleOwner, crossinline onChanged: (T) -> Boolean): Observer<T>

Observes this LiveData as long as onChanged returns true and returns the observer. The returned observer can be used to stop observing the LiveData when a callback is no longer desired. It is safe to remove the observer while it is executing or after onChanged returns true.

plusAssign

@MainThread

operator fun <E> MutableLiveData<List<E>>.plusAssign(element: E)

Adds the specified element to the end of this MutableLiveData. The observers are notified of the new value.

@MainThread

operator fun <E> MutableLiveData<List<E>>.plusAssign(elements: Iterable<E>)

Adds all of the elements of the specified collection to the end of this MutableLiveData. The observers are notified of the new value if the list was changed.

@MainThread

operator fun <K, V> MutableLiveData<Map<K, V>>.plusAssign(map: Map<K, V>)

Appends all entries from the given map in a LiveData, notifying observers of the new value. Creates a map if the LiveData has no value yet.

postValue

open override fun postValue(p0: T)

remove

@MainThread

fun <E> MutableLiveData<List<E>>.remove(element: E): Boolean

Removes a single instance of the specified element from a MutableLiveData, if it is present. The observers are notified of the new value if any of the specified elements was removed.

removeAll

@MainThread

fun <E> MutableLiveData<List<E>>.removeAll(predicate: (E) -> Boolean): Boolean

Removes all elements from this MutableLiveData that match the given predicate. The observers are notified of the new value if the list was changed.

@MainThread

fun <E> MutableLiveData<List<E>>.removeAll(elements: Iterable<E>): Boolean

Removes all elements from this MutableLiveData that are also contained in the given elements collection. The observers are notified of the new value if the list was changed.

removeObserver

@MainThread

open fun removeObserver(@NonNull p0: Observer<in T>)

removeObservers

@MainThread

open fun removeObservers(@NonNull p0: LifecycleOwner)

requireValue

fun <T : R?, R : Any> LiveData<T>.requireValue(): R

Gets the value stored in the LiveData object that should not be null.

set

@MainThread

operator fun <K, V> MutableLiveData<Map<K, V>>.set(key: K, valueToAdd: V)

Maps key to valueToAdd in LiveData's value. Creates a map if the LiveData has no value yet.

withSetter

fun <T> LiveData<T>.withSetter(setter: (T) -> Unit): MutableLiveData<T>

Creates a MutableLiveData from LiveData by specifying the setter to use to the change the value.