Copyright (c) 2016-present, RxJava Contributors.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is
distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
the License for the specific language governing permissions and limitations under the License.
/**
* Copyright (c) 2016-present, RxJava Contributors.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is
* distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
* the License for the specific language governing permissions and limitations under the License.
*/
package io.reactivex.observers;
import io.reactivex.Observer;
import io.reactivex.annotations.NonNull;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.util.EndConsumerHelper;
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) <class name> 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(Observer) instead of the standard subscribe() method.
Example
Observable.range(1, 5)
.subscribe(new DefaultObserver<Integer>() {
@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!");
}
});
Type parameters: - <T> – the value type
/**
* Abstract base implementation of an {@link io.reactivex.Observer Observer} with support for cancelling a
* subscription via {@link #cancel()} (synchronously) and calls {@link #onStart()}
* when the subscription happens.
*
* <p>All pre-implemented final methods are thread-safe.
*
* <p>Use the protected {@link #cancel()} to dispose the sequence from within an
* {@code onNext} implementation.
*
* <p>Like all other consumers, {@code DefaultObserver} can be subscribed only once.
* Any subsequent attempt to subscribe it to a new source will yield an
* {@link IllegalStateException} with message {@code "It is not allowed to subscribe with a(n) <class name> multiple times."}.
*
* <p>Implementation of {@link #onStart()}, {@link #onNext(Object)}, {@link #onError(Throwable)}
* and {@link #onComplete()} are not allowed to throw any unchecked exceptions.
* If for some reason this can't be avoided, use {@link io.reactivex.Observable#safeSubscribe(io.reactivex.Observer)}
* instead of the standard {@code subscribe()} method.
*
* <p>Example<pre><code>
* Observable.range(1, 5)
* .subscribe(new DefaultObserver<Integer>() {
* @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!");
* }
* });
* </code></pre>
*
* @param <T> the value type
*/
public abstract class DefaultObserver<T> implements Observer<T> {
private Disposable upstream;
@Override
public final void onSubscribe(@NonNull Disposable d) {
if (EndConsumerHelper.validate(this.upstream, d, getClass())) {
this.upstream = d;
onStart();
}
}
Cancels the upstream's disposable.
/**
* Cancels the upstream's disposable.
*/
protected final void cancel() {
Disposable upstream = this.upstream;
this.upstream = DisposableHelper.DISPOSED;
upstream.dispose();
}
Called once the subscription has been set on this observer; override this
to perform initialization.
/**
* Called once the subscription has been set on this observer; override this
* to perform initialization.
*/
protected void onStart() {
}
}