问题描述
最近在使用RxJava时，出现了一个错误，错误日志如下：
02-28 09:42:16.962 16647-17731/com.aspire.mpus E/AndroidRuntime: FATAL EXCEPTION: RxCachedThreadScheduler-1
Process: com.aspire.mpus, PID: 16647
java.lang.Throwable: 网络连接超时
at com.aspire.mpus.core.api.Api.onError(Api.java:84)
at com.aspire.mpus.core.api.Api.access$100(Api.java:23)
at com.aspire.mpus.core.api.Api$1.subscribe(Api.java:116)
at io.reactivex.internal.operators.observable.ObservableCreate.subscribeActual(ObservableCreate.java:40)
at io.reactivex.Observable.subscribe(Observable.java:10514)
at io.reactivex.internal.operators.observable.ObservableSubscribeOn$1.run(ObservableSubscribeOn.java:39)
at io.reactivex.Scheduler$1.run(Scheduler.java:134)
at io.reactivex.internal.schedulers.ScheduledRunnable.run(ScheduledRunnable.java:59)
at io.reactivex.internal.schedulers.ScheduledRunnable.call(ScheduledRunnable.java:51)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:269)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
抛出异常的原因是我在onError方法中会指定一些错误的原因，例如网络连接超时、连接服务器失败等。
private void onError(Exception e, ObservableEmitter emitter, String message) {
e.printStackTrace();
LogUtils.error(e);
if (e instanceof SocketTimeoutException) {
emitter.onError(new Throwable("网络连接超时"));
} else if (e instanceof ConnectException) {
emitter.onError(new Throwable("连接服务器失败"));
} else {
emitter.onError(new Throwable(message));
}
emitter.onComplete();
}
解决方法
判断emitter是否被取消订阅。如果当前的emitter未被取消订阅，则正常抛出异常，否则不执行。
private void onError(Exception e, ObservableEmitter emitter, String message) {
e.printStackTrace();
LogUtils.error(e);
if (!emitter.isDisposed()) {
if (e instanceof SocketTimeoutException) {
emitter.onError(new Throwable("网络连接超时"));
} else if (e instanceof ConnectException) {
emitter.onError(new Throwable("连接服务器失败"));
} else {
emitter.onError(new Throwable(message));
}
emitter.onComplete();
}
}
重现步骤
- 开始一个网络请求
- 在请求未结束时结束当前页面
- 请求结束后，如果未能请求成功，则onError方法中会判断异常信息，并抛出异常，但是Observable未能捕捉到异常，最终导致APP crash
Observable生命周期管理
在执行网络请求时，会生成一个Disposable对象，该对象保存了Observable的状态（订阅、取消订阅）。
查看ObservableEmitter源码，
public interface ObservableEmitter<T> extends Emitter<T> {
/**
* Sets a Disposable on this emitter; any previous Disposable
* or Cancellation will be unsubscribed/cancelled.
* @param d the disposable, null is allowed
*/
void setDisposable(@Nullable Disposable d);
/**
* Sets a Cancellable on this emitter; any previous Disposable
* or Cancellation will be unsubscribed/cancelled.
* @param c the cancellable resource, null is allowed
*/
void setCancellable(@Nullable Cancellable c);
/**
* Returns true if the downstream disposed the sequence.
* @return true if the downstream disposed the sequence
*/
boolean isDisposed();
/**
* Ensures that calls to onNext, onError and onComplete are properly serialized.
* @return the serialized ObservableEmitter
*/
@NonNull
ObservableEmitter<T> serialize();
}
发现ObservableEmitter也持有Disposable的属性，所以增加对当前订阅事件的判断，然后选择是否抛出异常，即可解决问题。
