Introduction

Type-safe HTTP client for Android and Java by Square, Inc.

In Retrofit 1.x, there is no direct way to cancel an active task, you need to do it manually, which turns out pretty hard.

In Retrofit 2.0, Square implemented this functionality.

Import

You can add couple of lines in the build.gradle of your module.(You should check the lastest version beforehand.)

compile 'com.squareup.retrofit2:converter-gson:2.1.0'

As Retrofit 2.0 is based on OkHttp, we need OkHttp as well:

compile 'com.squareup.okhttp3:okhttp:3.4.1'

And I will use Gson as my Converter:

compile 'com.squareup.retrofit2:converter-gson:2.1.0'

Interface

You need an interface to define the request. Here I use Github-Api to fetch the information of all repos of a specific user.

Annotation is pretty important here, it defines request method and the variables in the url.

public interface GithubAPIService {
    @GET("/users/{owner}/repos")
    Call<List<RepoInfo>> repoList(
            @Path("owner") String userName
    );
}

Note that use {xxx} to insert variable into the url and use Call<T> to state your request in which you define the variable.

And here RepoInfo is a Java Object class including the member variable about a repo, just like repoName, description and so on.

public class RepoInfo {
    @SerializedName("name")
    public String repoName = null;
    public String description = null;
    @SerializedName("fork")
    public boolean isForked = false;
    @SerializedName("language")
    public String codeLang = null;
    @SerializedName("forks_count")
    public int forkCount = 0;
    @SerializedName("stargazers_count")
    public int StarCount = 0;
}

The annotation SerializedName is something about Gson, you can click here to see how it works.

Send Request

First of all, you need to instantiate the Retrofit：

GithubAPIService githubAPIService = mRetrofit.create(GithubAPIService.class);

Then, instantiate the call and put it into a queue:

final Call<List<RepoInfo>> call = githubAPIService.repoList(userName);
call.enqueue(new Callback<List<RepoInfo>>() {
    @Override
    public void onResponse(Call<List<RepoInfo>> call, Response<List<RepoInfo>> response) {
        for (RepoInfo repoInfo : response.body()) {
            Log.d("TAG", repoInfo.repoName);
        }
    }
    @Override
    public void onFailure(Call<List<RepoInfo>> call, Throwable t) {}
});

Attention, the method onResponse will still be invoked if the response can’t be decoded, and the response.body() will be null. And the method will also be invoked even if there is a 404 error, and in this case we can get the error information from response.errorBody().

Cancel Request

As I say at the first of this post, a request can be easily cancelled:

call.cancel();

Source code

You can check the source code in GithubApiService.java and RetrofitActivity.java in my another repo.