問題描述
最近在使用RxJava時，出現了一個錯誤，錯誤日志如下：
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: 網絡連接超時
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)
拋出異常的原因是我在onError方法中會指定一些錯誤的原因，例如網絡連接超時、連接服務器失敗等。
private void onError(Exception e, ObservableEmitter emitter, String message) {
e.printStackTrace();
LogUtils.error(e);
if (e instanceof SocketTimeoutException) {
emitter.onError(new Throwable("網絡連接超時"));
} else if (e instanceof ConnectException) {
emitter.onError(new Throwable("連接服務器失敗"));
} else {
emitter.onError(new Throwable(message));
}
emitter.onComplete();
}
解決方法
判斷emitter是否被取消訂閱。如果當前的emitter未被取消訂閱，則正常拋出異常，否則不執行。
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("網絡連接超時"));
} else if (e instanceof ConnectException) {
emitter.onError(new Throwable("連接服務器失敗"));
} else {
emitter.onError(new Throwable(message));
}
emitter.onComplete();
}
}
重現步驟
- 開始一個網絡請求
- 在請求未結束時結束當前頁面
- 請求結束后，如果未能請求成功，則onError方法中會判斷異常信息，并拋出異常，但是Observable未能捕捉到異常，最終導致APP crash
Observable生命周期管理
在執行網絡請求時，會生成一個Disposable對象，該對象保存了Observable的狀態（訂閱、取消訂閱）。
查看ObservableEmitter源碼，
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();
}
發現ObservableEmitter也持有Disposable的屬性，所以增加對當前訂閱事件的判斷，然后選擇是否拋出異常，即可解決問題。
