io.reactivex.rxjava3.observers

Class DefaultObserver

java.lang.Object

io.reactivex.rxjava3.observers.DefaultObserver

Type Parameters:

T - the value type

All Implemented Interfaces:

Observer

public abstract class DefaultObserver
extends Object
implements Observer

Abstract base implementation of an Observer with support for cancelling a subscription via cancel() (synchronously) and calls onStart() when the subscription happens.

All pre-implemented final methods are thread-safe.

Use the protected cancel() to dispose the sequence from within an onNext implementation.

Like all other consumers, DefaultObserver can be subscribed only once. Any subsequent attempt to subscribe it to a new source will yield an IllegalStateException with message "It is not allowed to subscribe with a(n) multiple times.".

Implementation of onStart(), Observer.onNext(Object), Observer.onError(Throwable) and Observer.onComplete() are not allowed to throw any unchecked exceptions. If for some reason this can't be avoided, use Observable.safeSubscribe(io.reactivex.rxjava3.core.Observer) instead of the standard subscribe() method.

Example

 Observable.range(1, 5)
     .subscribe(new DefaultObserver() {
         @Override public void onStart() {
             System.out.println("Start!");
         }
         @Override public void onNext(Integer t) {
             if (t == 3) {
                 cancel();
             }
             System.out.println(t);
         }
         @Override public void onError(Throwable t) {
             t.printStackTrace();
         }
         @Override public void onComplete() {
             System.out.println("Done!");
         }
     });
 

Constructor Summary

Constructors

Constructor and Description
DefaultObserver()

Method Summary

Modifier and Type	Method and Description
protected void	cancel() Cancels the upstream's disposable.
protected void	onStart() Called once the subscription has been set on this observer; override this to perform initialization.
void	onSubscribe(@NonNull Disposable d) Provides the Observer with the means of cancelling (disposing) the connection (channel) with the Observable in both synchronous (from within Observer.onNext(Object)) and asynchronous manner.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface io.reactivex.rxjava3.core.Observer

onComplete, onError, onNext

Constructor Detail

DefaultObserver

public DefaultObserver()

Method Detail

onSubscribe

public final void onSubscribe(@NonNull
                              @NonNull Disposable d)

Description copied from interface: Observer

Provides the Observer with the means of cancelling (disposing) the connection (channel) with the Observable in both synchronous (from within Observer.onNext(Object)) and asynchronous manner.

Specified by:

onSubscribe in interface Observer<T>

Parameters:

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

cancel

protected final void cancel()

Cancels the upstream's disposable.

onStart

protected void onStart()

Called once the subscription has been set on this observer; override this to perform initialization.