通过具体的示例，学习每个操作符的用法~

1.OnErrorResumeNext ⭐️

OnErrorResumeNext操作符返回一个备用的Observable，当原Observable调用onError时，OnErrorResueNext操作符将开始从备用的Observable发送事件。

示例:

Observable.create(object : ObservableOnSubscribe<Int> {
        override fun subscribe(emitter: ObservableEmitter<Int>) {
            emitter.onNext(1)
            emitter.onNext(2)
            emitter.onError(IllegalArgumentException())
            emitter.onNext(3)
            emitter.onComplete()
        }
    }).onErrorResumeNext(object : Function<Throwable, ObservableSource<Int>> {
        override fun apply(t: Throwable): ObservableSource<Int> {
            return Observable.just(404)
        }
    })
    .subscribe(object : Observer<Int> {
        override fun onSubscribe(d: Disposable) {
            Log.e(TAG, "---------onSubscribe---------")
        }
        override fun onNext(t: Int) {
            Log.e(TAG, "---------onNext--------${t}-")
        }
        override fun onError(e: Throwable) {
            Log.e(TAG, "---------onError---------")
        }
        override fun onComplete() {
            Log.e(TAG, "---------onComplete---------")
        }
    })

输出结果：

2022-11-27 20:40:18.589 E/ErrorOperator: ---------onSubscribe---------
2022-11-27 20:40:18.590 E/ErrorOperator: ---------onNext--------1-
2022-11-27 20:40:18.590 E/ErrorOperator: ---------onNext--------2-
2022-11-27 20:40:18.590 E/ErrorOperator: ---------onNext--------404-
2022-11-27 20:40:18.590 E/ErrorOperator: ---------onComplete---------

2.OnErrorReturn

当原Observable调用onError时,onErrorReturn/onErrorReturnItem不会将该错误传播给下游观测者，而是会发出指定的项并调用观测者的onCompleted方法。

示例：

 Observable.create(object : ObservableOnSubscribe<Int> {
        override fun subscribe(emitter: ObservableEmitter<Int>) {
            emitter.onNext(1)
            emitter.onNext(2)
            emitter.onError(IllegalArgumentException())
            emitter.onNext(3)
            emitter.onComplete()
        }
    }).onErrorReturn(object : Function<Throwable, Int> {
        override fun apply(t: Throwable): Int {
            return 500
        }
    })
    .subscribe(object : Observer<Int> {
        override fun onSubscribe(d: Disposable) {
            Log.e(TAG, "---------onSubscribe---------")
        }
        override fun onNext(t: Int) {
            Log.e(TAG, "---------onNext--------${t}-")
        }
        override fun onError(e: Throwable) {
            Log.e(TAG, "---------onError---------")
        }
        override fun onComplete() {
            Log.e(TAG, "---------onComplete---------")
        }
    })

输出结果：

2022-11-27 20:40:18.589 E/ErrorOperator: ---------onSubscribe---------
2022-11-27 20:40:18.590 E/ErrorOperator: ---------onNext--------1-
2022-11-27 20:40:18.590 E/ErrorOperator: ---------onNext--------2-
2022-11-27 20:40:18.590 E/ErrorOperator: ---------onNext--------404-
2022-11-27 20:40:18.590 E/ErrorOperator: ---------onComplete---------

示例2：

Observable.create(object : ObservableOnSubscribe<Int> {
        override fun subscribe(emitter: ObservableEmitter<Int>) {
            emitter.onNext(1)
            emitter.onNext(2)
            emitter.onError(IllegalArgumentException())
            emitter.onNext(3)
            emitter.onComplete()
        }
    })
    .onErrorReturnItem(400)
    .subscribe(object : Observer<Int> {
        override fun onSubscribe(d: Disposable) {
            Log.e(TAG, "---------onSubscribe---------")
        }
        override fun onNext(t: Int) {
            Log.e(TAG, "---------onNext--------${t}-")
        }
        override fun onError(e: Throwable) {
            Log.e(TAG, "---------onError---------")
        }
        override fun onComplete() {
            Log.e(TAG, "---------onComplete---------")
        }
    })

输出结果：

2022-11-27 21:27:51.613 E/ErrorOperator: ---------onSubscribe---------
2022-11-27 21:27:51.613 E/ErrorOperator: ---------onNext--------1-
2022-11-27 21:27:51.613 E/ErrorOperator: ---------onNext--------2-
2022-11-27 21:27:51.613 E/ErrorOperator: ---------onNext--------400-
2022-11-27 21:27:51.613 E/ErrorOperator: ---------onComplete--------

3.Retry ⭐️

如果源Observable发出错误，请重新订阅它，希望它能无错误地完成。 

示例：

Observable.create(object : ObservableOnSubscribe<Int> {
        override fun subscribe(emitter: ObservableEmitter<Int>) {
            emitter.onNext(1)
            emitter.onNext(2)
            emitter.onError(IllegalArgumentException())
            emitter.onNext(3)
            emitter.onComplete()
        }
    })
    .retry(object : BiPredicate<Int, Throwable> {
        override fun test(times: Int, throwable: Throwable): Boolean {
            if (times > 2) {
                return false
            }
            return true
        }
    })
    .subscribe(object : Observer<Int> {
        override fun onSubscribe(d: Disposable) {
            Log.e(TAG, "---------onSubscribe---------")
        }
        override fun onNext(t: Int) {
            Log.e(TAG, "---------onNext--------${t}-")
        }
        override fun onError(e: Throwable) {
            Log.e(TAG, "---------onError---------")
        }
        override fun onComplete() {
            Log.e(TAG, "---------onComplete---------")
        }
    })

输出结果：

2022-11-27 21:40:23.221 E/ErrorOperator: ---------onSubscribe---------
2022-11-27 21:40:23.222 E/ErrorOperator: ---------onNext--------1-
2022-11-27 21:40:23.222 E/ErrorOperator: ---------onNext--------2-
2022-11-27 21:40:23.222 E/ErrorOperator: ---------onNext--------1-
2022-11-27 21:40:23.222 E/ErrorOperator: ---------onNext--------2-
2022-11-27 21:40:23.222 E/ErrorOperator: ---------onNext--------1-
2022-11-27 21:40:23.223 E/ErrorOperator: ---------onNext--------2-
2022-11-27 21:40:23.223 E/ErrorOperator: ---------onError---------