Cannot find symbol class EmptyResultSetException when using Android Room Database with RXJava2

Question

I'm trying to use RXJava2 with Room database . I use Single Observable to get a list of my object . But every time I get this error

cannot find symbol class EmptyResultSetException

I'm using this tutorial ANDROID ROOM PERSISTENT AND RXJAVA2

I used it before with AsyncTask without RXJava and it worked so I wanted to use it with RXJava

Here is my build.gradle

apply plugin: 'com.android.application'

  android {
compileSdkVersion 28
defaultConfig {
    applicationId "apit.net.sa.simpleusingroom"
    minSdkVersion 16
    targetSdkVersion 28
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    }
}
}

    dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'




implementation 'com.android.support:support-v13:28.0.0'
implementation 'com.android.support:recyclerview-v7:28.0.0'
implementation 'com.android.support:design:28.0.0'
implementation 'com.jakewharton:butterknife:8.5.1'
    //ROOM database
implementation 'android.arch.persistence.room:runtime:1.0.0'
annotationProcessor 'android.arch.persistence.room:compiler:1.0.0'

//RXJava2
implementation 'io.reactivex.rxjava2:rxjava:2.1.9'
implementation 'io.reactivex.rxjava2:rxandroid:2.0.1'

//RXjava with room
implementation 'android.arch.persistence.room:rxjava2:1.0.0-alpha1'

annotationProcessor 'com.jakewharton:butterknife-compiler:8.5.1'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
 }

Dao Class

 @Query("SELECT * FROM UserEntity")
Single<List<UserEntity>> getUsersSingle();

MyActivity

DatabaseSingInstance.getInstance(this)
            .getOurDatabase()
            .userDAO()
            .getUsersSingle()
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(new DisposableSingleObserver<List<UserEntity>>() {


                @Override
                public void onSuccess(final List<UserEntity> userEntities) {
                    adapter = new UserAdapter(userEntities, MainActivity.this, new UserAdapter.OnLongClickListner() {
                        @Override
                        public void onClick(int position) {
                            showPopupWindow(userEntities,position);
                        }
                    });
                    myRec.setAdapter(adapter);
                }

                @Override
                public void onError(Throwable e) {
                    Log.e("error"," "+e.getMessage());
                }


            });

Answer 1

I solved the problem according to this Answer

I just changed the room_version to 1.1.0 . By the way I'm waiting for any one who can explain this error or just explain why it happened .