How to Handle Api Call Using Rxjava2 and Retrofit2 in android

manish choudhary

6 March 2021

In this blog we are going handle api calls using Rxjava and Retrofit library which makes simple and cleaner way to define API.

RxJava is a Java VM implementation of Reactive Extensions a library for composing asynchronous and event-based programs by using observable sequences.

Retrofit is a REST Client for Android and Java. It makes it relatively easy to retrieve and upload JSON. Retrofit uses the OkHttp library for HTTP requests.

Add the following dependencies to your gradle file

compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
compile 'com.jakewharton.retrofit:retrofit2-rxjava2-adapter:1.0.0'
compile 'com.google.code.gson:gson:2.7'
compile 'com.squareup.retrofit2:retrofit:2.0.2'
compile 'com.squareup.retrofit2:converter-gson:2.0.2'

compile 'io.reactivex.rxjava2:rxandroid:2.0.1'

compile 'com.jakewharton.retrofit:retrofit2-rxjava2-adapter:1.0.0'

compile 'com.google.code.gson:gson:2.7'

compile 'com.squareup.retrofit2:retrofit:2.0.2'

compile 'com.squareup.retrofit2:converter-gson:2.0.2'

Once the dependencies are all set up, We would need an instance of Retrofit to make network calls.

baseUrl-> Set up Base URL of API

addConverterFactory() — converter factory for serialization and deserialization of objects

 Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl(Constants.BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create())
                    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                    .client(oktHttpClient.build())
                    .build();

Retrofit retrofit = new Retrofit.Builder()

.baseUrl(Constants.BASE_URL)

.addConverterFactory(GsonConverterFactory.create())

.addCallAdapterFactory(RxJava2CallAdapterFactory.create())

.client(oktHttpClient.build())

.build();

We can define post parameter for the API. The APIs are declared in an interface:

    @FormUrlEncoded
    @POST(HOME_PAGE_API)
    Observable<HomeDataModel> gethomedataRx(
            @Field("width") String width,
            @Field("show_category") int category,
            @Field("count") String count,
            @Field("mfactor") String mfactor,
            @Field("wk_token") String wk_token
    );

@FormUrlEncoded

@POST(HOME_PAGE_API)

Observable<HomeDataModel> gethomedataRx(

@Field("width") String width,

@Field("show_category") int category,

@Field("count") String count,

@Field("mfactor") String mfactor,

@Field("wk_token") String wk_token

);

In Rx, the subscriber implements three methods to interact with observable:

onNext(Data): Receives the data from the observable
onError(Exception): Gets called if an exception is thrown
onCompleted(): Gets called when the data stream ends

For Android, to subscribe to an observable, we first tell the observable about the threads on which we plan to subscribe to and observe.

Making an API call:

        Observable<HomeDataModel> observable = ApiClient.getClient(mContext).create(ApiInteface.class)
                    .gethomedataRx(getScreenWidth(),0, "4", "1", 
                    SharedPreference.getWkToken(mContext, Constants.CUSTOMER_SHARED_PREFERENCE_KEY_WK_TOKEN));

            observable.subscribe(new Observer<BaseModel>() {
                @Override
                public void onSubscribe(Disposable d) {

                }

                @Override
                public void onNext(BaseModel value) {
                    Log.d("RxJAVACall", "onNext: --------->" + value);
                }

                @Override
                public void onError(Throwable e) {

                }

                @Override
                public void onComplete() {
                    Log.d("RxJAVACall", "DONE: --------->");
                }
            });

Observable<HomeDataModel> observable = ApiClient.getClient(mContext).create(ApiInteface.class)

.gethomedataRx(getScreenWidth(),0, "4", "1",

SharedPreference.getWkToken(mContext, Constants.CUSTOMER_SHARED_PREFERENCE_KEY_WK_TOKEN));

observable.subscribe(new Observer<BaseModel>() {

@Override

public void onSubscribe(Disposable d) {

}

@Override

public void onNext(BaseModel value) {

Log.d("RxJAVACall", "onNext: --------->" + value);

}

@Override

public void onError(Throwable e) {

}

@Override

public void onComplete() {

Log.d("RxJAVACall", "DONE: --------->");

}

});

That’s it, we can use the Observable/Flowable returned by the API and subscribe() to it to handle the data

Merging the multiple requests in Rxandroid

Merge operator combine multiple observable into one

            Observable.merge(Observable1,Observable2).subscribe(new Observer<BaseModel>() {
                @Override
                public void onSubscribe(Disposable d) {

                }

                @Override
                public void onNext(BaseModel value) {
                    Log.d("RxJAVACall", "onNext: --------->" + value);
                }

                @Override
                public void onError(Throwable e) {

                }

                @Override
                public void onComplete() {
                    Log.d("RxJAVACall", "DONE: --------->");
                }
            });

Observable.merge(Observable1,Observable2).subscribe(new Observer<BaseModel>() {

@Override

public void onSubscribe(Disposable d) {

}

@Override

public void onNext(BaseModel value) {

Log.d("RxJAVACall", "onNext: --------->" + value);

}

@Override

public void onError(Throwable e) {

}

@Override

public void onComplete() {

Log.d("RxJAVACall", "DONE: --------->");

}

});