Implementation of Idling Resource

[troy21688]

I am using Retrofit to pull data from the web and then display in a RecyclerView.

Also, I am testing clicks and views of the RecyclerView.

My Espresso test is passing on my emulator, but on my device (Google Nexus 6), it is not passing.

I believe it may a be a case of idling resources, and wanted to see if this library would be the solution and how to implement:

Main Activity with Retrofit:

```
 public class MainActivity extends AppCompatActivity {

private RecyclerView mRecipeList;
private static final String BASE_URL = "https://d17h27t6h515a5.cloudfront.net/";
private List<Recipe> mRecipeListResponse;
private MyAdapter mAdapter;
ConstraintLayout mConstraintLayoutSmall;

//testing

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //TODO: Unable to set dynamic, material RecyclerView using Constraints; had to set static DP for height of view
    //TODO: See StackOverflow post: https://stackoverflow.com/questions/51529326/constraintlayout-unable-to-wrap-content-and-stack-recyclerview-items?noredirect=1#comment90046855_51539365
    mRecipeList = findViewById(R.id.recycler_view_ingredients);
    mConstraintLayoutSmall = findViewById(R.id.small_layout);
    int spanCount = calculateNoOfColumns(getApplicationContext());

    LinearLayoutManager lm = new LinearLayoutManager(getApplicationContext());
    lm.setOrientation(LinearLayoutManager.VERTICAL);

    GridLayoutManager glm = new GridLayoutManager(this, spanCount);
    glm.setOrientation(LinearLayoutManager.VERTICAL);

    //check if landscape mode
    if (getApplicationContext().getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE && mConstraintLayoutSmall != null) {
        mRecipeList.setLayoutManager(glm);
    } else {
        mRecipeList.setLayoutManager(lm);
    }

     callToRetrofit();

   }

private void callToRetrofit() {
    HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
    interceptor.setLevel(HttpLoggingInterceptor.Level.BASIC);
    OkHttpClient client = new OkHttpClient
            .Builder()
            .addInterceptor(interceptor)
            .build();

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

    final ApiInterface apiInterface = retrofit.create(ApiInterface.class);
    Call<List<Recipe>> call = apiInterface.getRecipe();
    call.enqueue(new Callback<List<Recipe>>() {
        @Override
        public void onResponse(Call<List<Recipe>> call, Response<List<Recipe>> response) {
            Log.v("TAG", String.valueOf(response.isSuccessful()));
            mRecipeListResponse = response.body();
            for (Recipe recipe : mRecipeListResponse){
                Log.v("ID", recipe.getId().toString());
                Log.v("SIZE", String.valueOf(mRecipeListResponse.size()));
            }

            mAdapter = new MyAdapter(MainActivity.this);
            mAdapter.setDataSet(mRecipeListResponse);
            mRecipeList.setAdapter(mAdapter);
                          }

        @Override
        public void onFailure(Call<List<Recipe>> call, Throwable t) {
            Log.v("TAG", t.getMessage());
        }
    });


}

public static int calculateNoOfColumns(Context context) {
    DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();
    float dpWidth = displayMetrics.widthPixels / displayMetrics.density;
    int scalingFactor = 200;
    int noOfColumns = (int) (dpWidth / scalingFactor);
    if(noOfColumns < 2)
        noOfColumns = 2;
    return noOfColumns;
}

public interface ApiInterface{
    @GET("topher/2017/May/59121517_baking/baking.json")
    Call<List<Recipe>> getRecipe();
}

}

Espresso Testing:


    ```
   @RunWith(AndroidJUnit4.class)
   public class EspressoTest {


    @Rule
    public ActivityTestRule<MainActivity> firstRule = new ActivityTestRule<>(MainActivity.class);


    @Test
    public void testRecyclerViewClick() {
        Espresso.onView(ViewMatchers.withId(R.id.recycler_view_ingredients)).perform(RecyclerViewActions.actionOnItemAtPosition(0, click()));
    }

    //TODO: This test is not passing on my device, but it is passing on an emulator. I am not sure why, but have read about idling resources. Can you confirm how to handle?
    @Test
    public void testRecyclerViewText(){
        Espresso.onView(ViewMatchers.withId(R.id.recycler_view_ingredients)).perform(RecyclerViewActions.scrollToPosition(0));
        Espresso.onView(withText("Nutella Pie")).check(matches(isDisplayed()));
    }

}