How to count RecyclerView items with Espresso

Question

Using Espresso and Hamcrest,

How can I count items number available in a recyclerView?

Exemple: I would like check if 5 items are displaying in a specific Re

Answer 1

To complete nenick answer and provide and little bit more flexible solution to also test if item cout is greaterThan, lessThan ...

public class RecyclerViewItemCountAssertion implements ViewAssertion {

    private final Matcher matcher;

    public RecyclerViewItemCountAssertion(int expectedCount) {
        this.matcher = is(expectedCount);
    }

    public RecyclerViewItemCountAssertion(Matcher matcher) {
        this.matcher = matcher;
    }

    @Override
    public void check(View view, NoMatchingViewException noViewFoundException) {
        if (noViewFoundException != null) {
            throw noViewFoundException;
        }

        RecyclerView recyclerView = (RecyclerView) view;
        RecyclerView.Adapter adapter = recyclerView.getAdapter();
        assertThat(adapter.getItemCount(), matcher);
    }

}

Usage:

onView(withId(R.id.recyclerView)).check(new RecyclerViewItemCountAssertion(5));
onView(withId(R.id.recyclerView)).check(new RecyclerViewItemCountAssertion(greaterThan(5));
onView(withId(R.id.recyclerView)).check(new RecyclerViewItemCountAssertion(lessThan(5));
// ...