Retrofit 2 : REST Client for Android

Using RxJava with Retrofit

Add the following dependencies in Module level build.gradle file:

dependencies {

   /// ...
    // Add Retrofit
    implementation 'com.squareup.retrofit2:retrofit:2.5.0'
    // Using gson as converter
    implementation 'com.squareup.retrofit2:converter-gson:2.5.0'
    // A Converter which supports converting strings and both primitives and their boxed types to text/plain bodies.
    implementation 'com.squareup.retrofit2:converter-scalars:2.5.0'

    implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'
    // Because RxAndroid releases are few and far between, it is recommended you also
    // explicitly depend on RxJava's latest version for bug fixes and new features.
    // (see https://github.com/ReactiveX/RxJava/releases for latest 2.x.x version)
    implementation 'io.reactivex.rxjava2:rxjava:2.2.8'
    implementation 'com.squareup.retrofit2:adapter-rxjava2:2.5.0'

    implementation 'com.squareup.okhttp3:logging-interceptor:3.14.0'
    androidTestImplementation 'com.android.support.test:rules:1.0.2'
    testImplementation 'androidx.test:runner:1.3.0-alpha02'
}

Create an interface called ApiInterface.java with the following lines:

interface ApiService {

    @Headers("Content-Type: application/json")
    @PUT("glucose-upload")
    fun uploadGlucose(@Body str:String): Call<String>

    @Headers("Content-Type: application/json")
    @PUT("glucose-upload")
    fun uploadGlucose2(@Body str:String): Observable<String>
}

In your Activity file(or wherever you want to make the API call), add the following lines:

Retrofit retrofit = new Retrofit.Builder()
                .client(new OkHttpClient())
                .baseUrl("https://baseurl")
                .addConverterFactory(ScalarsConverterFactory.create())
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .build();

        ApiService service = retrofit.create(ApiService.class);
String str = "{}"; // Sending empty JSON as Request body.

Observable<String> call = service.uploadGlucose2(str);
        call.subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Observer<String>() {
                    @Override
                    public void onSubscribe(Disposable d) {
                        Log.d(TAG, "onSubscribe: " + d.isDisposed());
                    }

                    @Override
                    public void onNext(String s) {
                        // Main Data is produced here.
                        Log.d(TAG, "onNext: " + s);
                    }

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

                    @Override
                    public void onComplete() {
                        Log.d(TAG, "onComplete: ");
                    }
                });


You can now run the app and see the Log output from the Run tab as shown below:

In Postman the response looks like the following:

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Suggested Reading:


https://inthecheesefactory.com/blog/retrofit-2.0/en



https://github.com/codepath/android_guides/wiki/Consuming-APIs-with-Retrofit