Yet another MVP article — Part 3: Calling APIs using Retrofit

Implementing a sample Android Application using MVP , RxJava , Dagger 2 , Retrofit2 , Test , and all the brand new modern methods and libraries Previously on this article… _Implementing a sample Android Application using MVP, RxJava, Dagger 2, Retrofit2, Test, and all the brand new modern…_hackernoon.com Yet another MVP article — Part 2: How Dagger helps with the project Let’s think that you have studied and which means you know everything about modules and structure and also get more familiar with Dagger usage in wiring up layers. part1 part2 the sample project’s MVP now let’s continue… Let’s get into network and API: Almost all mobile application communicate with their services using the internet. is a perfect library contributed by which can always come handy and help you with developing a network layer for your application. Retrofit Jake Wharton Android Long story short, in this project uses an interface called which shows the way to API: Retrofit, MarvelApi Using is really simple, as you can see there is a method located at which needed some parameters to retrieve what you want, which is character data using its name. retrofit RESTful API http://gateway.marvel.com:80/v1/public/characters A good is the one who always read API documents, you can read more about Marvel APIs: developer _The Marvel developer portal gives Marvel fans, partners and other technologists access to an array of powerful APIs…_developer.marvel.com Marvel Developer Portal - Interactive Documentation , and in which MVP layer MarvelApi is located? All networking and databasing stuff happen inside layer. Model This layer only works with data and business logic and Presenter knows how to call or how to prepare data for the View layer. Please stop manipulating data within theModel layer and pass it safe and sound to the Presentation layer, he knows what to do… and more SOLID principle… According to “ ” of SOLID principle “ ”, then and have totally separated tasks to do. Single responsibility One chef can’t run the whole restaurant Model Presentation “One chef can’t run the whole restaurant”, — novoda Can we have a nice log of what we call and what we receive in API response? Why not! The library uses OkHttp library within which is a powerful network library. All magic happens with Interceptors. I will explain one by one and finally show you how to apply them to your OkHttpClient. Retrofit By a little configuration you can ask this library to show you a decent log in logcat which always comes handy: , but don’t forget to disable this logging thing in release version! you can do this by checking variable which generates during application build. BuildConfig.DEBUG How cache API results caused Database to vanish!!! First time I do this inside a news reader application, all database record updating and queries almost killed all team members. Using OkHttp cache feature you can handle header caches and also have an offline file caching which sometimes could be a perfect substitution for Database pain: There are two cache interceptors in this sample, One cache interceptor changes the header of API response and available caching for 2 minutes ( ), which means somehow debouncing user calls from API for 2min. maxAgeMin Another one is the offline interceptor, which uses cache directory (which provide using from module) to save API responses into files for 7 days ( ). Dagger app maxStaleDay Don’t panic if everything is new, you will learn how to use it after some sample project… ;) Do you trust network condition after an API call failure? No, then please retry! Network connections are always lossy or even the service might be down for a few seconds and they may cause trouble for the app, so please try again before informing the user about the situation! I look for retry policies using but none of them works with , but this interceptor works: RxJava Retrofit you can customize it if you require more retry times or even more condition to decide to retry or not, but I think it is fine. :) , and how to attach all interceptors to my OkHttp client? All interceptors are provided inside , which also add them all to OkHttpClient: ClientModule Take care of the statement which comes as the result of variable. if(isDebug) BuildConfig.DEBUG There is also the Network Timeout which tells OkHttp how long wait for the response. …Where is the Retrofit then! Okay, all these codings was for the final step… Inside we use that to create the instance and use it to create : ApiModule OkHttpClient Retrofit MarvelApi You have to provide that usually is the first static part of all your service API URLs, which in this sample is “http://gateway.marvel.com:80/”. (don’t forget the last ‘/’, it is required for the library and may cause exception) BaseUrl Retrofit API provided in this way would be used by which communicates with service. knows how to response using and you can easily capture the result parse it using Gson and use it with other (i.e map, flat map, filter, etc.) to manipulate and prepare a response and hand it to layer to present to the user. SearchInteractorImpl Retrofit RxJava RxJava operators View That’s it for now… Please clone the and get more familiar with it because in next part I will explain more about RxJava and RxAndroid and how it helps with spreading response from to layer. project repo from GitHub core View I look forward to your comments and helping for more improvements with this article. Share this article if you think it is useful, and follow me for more articles . Mohsen Mirhoseini To be continued… _Implementing a sample Android Application using MVP, RxJava, Dagger 2, Retrofit2, Test, and all the brand new modern…_hackernoon.com Yet another MVP article — Part 4: RxJava and RxAndroid know how to response