io.reactivex.rxjava3.core

Interface SingleObserver<T>

Type Parameters:

T - the type of item the SingleObserver expects to observe

All Known Implementing Classes:

DisposableSingleObserver, ResourceSingleObserver, SingleSubject, TestObserver

public interface SingleObserver<T>

Provides a mechanism for receiving push-based notification of a single value or an error.

When a SingleObserver is subscribed to a SingleSource through the SingleSource.subscribe(SingleObserver) method, the SingleSource calls onSubscribe(Disposable) with a Disposable that allows disposing the sequence at any time. A well-behaved SingleSource will call a SingleObserver's onSuccess(Object) method exactly once or the SingleObserver's onError(java.lang.Throwable) method exactly once as they are considered mutually exclusive terminal signals.

Calling the SingleObserver's method must happen in a serialized fashion, that is, they must not be invoked concurrently by multiple threads in an overlapping fashion and the invocation pattern must adhere to the following protocol:

    onSubscribe (onSuccess | onError)?

Subscribing a SingleObserver to multiple SingleSources is not recommended. If such reuse happens, it is the duty of the SingleObserver implementation to be ready to receive multiple calls to its methods and ensure proper concurrent behavior of its business logic.

Calling onSubscribe(Disposable), onSuccess(Object) or onError(Throwable) with a null argument is forbidden.

The implementations of the onXXX methods should avoid throwing runtime exceptions other than the following cases:

• If the argument is null, the methods can throw a NullPointerException. Note though that RxJava prevents nulls to enter into the flow and thus there is generally no need to check for nulls in flows assembled from standard sources and intermediate operators.
• If there is a fatal error (such as VirtualMachineError).

Since:

2.0

See Also:

ReactiveX documentation: Observable

Method Summary

Modifier and Type	Method and Description
void	onError(Throwable e) Notifies the SingleObserver that the Single has experienced an error condition.
void	onSubscribe(Disposable d) Provides the SingleObserver with the means of cancelling (disposing) the connection (channel) with the Single in both synchronous (from within onSubscribe(Disposable) itself) and asynchronous manner.
void	onSuccess(T t) Notifies the SingleObserver with a single item and that the Single has finished sending push-based notifications.

Method Detail

onSubscribe

void onSubscribe(@NonNull
                 Disposable d)

Provides the SingleObserver with the means of cancelling (disposing) the connection (channel) with the Single in both synchronous (from within onSubscribe(Disposable) itself) and asynchronous manner.

Parameters:

d - the Disposable instance whose Disposable.dispose() can be called anytime to cancel the connection

Since:

2.0

onSuccess

void onSuccess(@NonNull
               T t)

Notifies the SingleObserver with a single item and that the Single has finished sending push-based notifications.

The Single will not call this method if it calls onError(java.lang.Throwable).

Parameters:

t - the item emitted by the Single

onError

void onError(@NonNull
             Throwable e)

Notifies the SingleObserver that the Single has experienced an error condition.

If the Single calls this method, it will not thereafter call onSuccess(T).

Parameters:

e - the exception encountered by the Single