实现 retryWhen 逻辑

我有一个需要会话（cookie）来处理网络调用的应用程序。我在用着Retrofit+RxJava。但是，会话可能会过期（带有 401 未经授权状态的改造错误），在这种情况下我想重新进行身份验证（以获取新的 cookie）并重试之前的调用。我该怎么做RxJava?

我的例子：

getServerApi().getDialogs(offset, getCookies())
     .subscribeOn(Schedulers.newThread())
     .observeOn(AndroidSchedulers.mainThread())
     .retryWhen(observable -> {...}) // Need some logic
     .subscribe(dialogsEnvelope -> getView().setDialogs(dialogsEnvelope),
                throwable -> getView().setError(processFail(throwable)));

虽然Interceptor可能是这个特定问题的更好解决方案，该问题专门要求使用解决方案retryWhen，所以这是一种方法：

retryWhen(new Func1<Observable<Throwable>, Observable<?>>(){

    @Override
    public void Observable<?> call(Observable<Throwable>> attempts) {
        return attempts.flatMap(new Func1<Throwable, Observable<?>>() {

            @Override
            public Observable<?> call(Throwable throwable) {
                 if (throwable instanceof RetrofitError) {
                     RetrofitError retrofitError = (RetrofitError) throwable;
                     if (retrofitError.getKind() == RetrofitError.Kind.HTTP && retrofitError.getResponse().getStatus() == 401) {
                         // this is the error we care about - to trigger a retry we need to emit anything other than onError or onCompleted
                         return Observable.just(new Object());
                     } else {
                         // some other kind of error: just pass it along and don't retry
                         return Observable.error(throwable);
                     }
                 } else {
                     // some other kind of error: just pass it along and don't retry
                     return Observable.error(throwable);
                 }
             }
        });
    }
})

然而，你的getCookies在简单的情况下不会再次调用retry。那只会重新订阅相同的内容Observable but getCookies在创建之前被调用Observable。所以我认为你必须包装源代码的创建Observable in a defer.