RxJava3 on Android/Java: problem using SingleObserver (but Observer is fine!)

Question

The problem is that I can use an Observer but I can't use a SingleObserver. It gives me this error:

Inferred type 'E' for type parameter 'E' is not within its bound; should implement 'io.reactivex.rxjava3.core.Observer<? super com.xxx.Network.Response.ResponseLogin>'

and

.subscribeWith(new SingleObserver<ResponseLogin>(){
                ^
  required: E
  found: <anonymous SingleObserver<ResponseLogin>>
  reason: inferred type does not conform to upper bound(s)
    inferred: <anonymous SingleObserver<ResponseLogin>>
    upper bound(s): Observer<? super ResponseLogin>
  where E,T are type-variables:
    E extends Observer<? super ResponseLogin> declared in method <E>subscribeWith(E)
    T extends Object declared in class Observable

Here are some implementation details:

//build.gradle
    implementation "io.reactivex.rxjava3:rxandroid:3.0.0"
    implementation "io.reactivex.rxjava3:rxjava:3.0.2"

//ApiInterface.java
import io.reactivex.rxjava3.core.Observable;
...
public interface ServerAPIInterface {
    // For POST request
    @FormUrlEncoded
    @POST("/login")
    public Observable<ResponseLogin> login(
        // the POST params to server
        @Field("user_email") String user_email,
        @Field("user_password") String user_password
    );

and the fault is at:

import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers;
import io.reactivex.rxjava3.core.Observer;
import io.reactivex.rxjava3.core.SingleObserver;
import io.reactivex.rxjava3.disposables.CompositeDisposable;
import io.reactivex.rxjava3.disposables.Disposable;
import io.reactivex.rxjava3.schedulers.Schedulers;
...
        myApiInterface
                .login(myUserEmail, myPassword)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeWith(new SingleObserver<ResponseLogin>() {
                    @Override
                    public void onSuccess(ResponseLogin data) {
                        // update the adapter
                    }


                    @Override
                    public void onSubscribe(Disposable d) {
                        disposables.add(d);
                    }

                    @Override
                    public void onError(Throwable e) {
                        // display an error message
                    }
                });

If I replace SingleObserver with Observer (and implement all the required onXXX() methods it compiles OK. But I want a single observer.

Shall I downgrade to rxjava2 (untested)?

I suspect my imports are confused.

it seems there are 2 SingleObserver, another one is at io.reactivex.SingleObserver.

I did try to use these imports and skipped the rxjava3 prefix for most of them. However AndroidSchedulers can only be found in io.reactivex.rxjava3.android.schedulers.AndroidSchedulers.

question from:https://stackoverflow.com/questions/65908423/rxjava3-on-android-java-problem-using-singleobserver-but-observer-is-fine

Answer 1

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