A Kotlin implementation of the RecycleViewMatcher for Espresso

RecyclerViewMatcher.kt

import android.content.res.Resources;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import org.hamcrest.Description;
import org.hamcrest.Matcher;
import org.hamcrest.TypeSafeMatcher;

/**
* @author https://github.com/ebelli
**/
public class RecyclerViewMatcher {
    private final int recyclerViewId;

    public RecyclerViewMatcher(int recyclerViewId) {
        this.recyclerViewId = recyclerViewId;
    }

    public Matcher<View> atPosition(final int position) {
        return atPositionOnView(position, -1);
    }

    public Matcher<View> atPositionOnView(final int position, final int targetViewId) {

        return new TypeSafeMatcher<View>() {
            Resources resources = null;
            View childView;

            public void describeTo(Description description) {
                String idDescription = Integer.toString(recyclerViewId);
                if (this.resources != null) {
                    try {
                        idDescription = this.resources.getResourceName(recyclerViewId);
                    } catch (Resources.NotFoundException var4) {
                        idDescription = String.format("%s (resource name not found)",
                                new Object[] { Integer.valueOf
                                        (recyclerViewId) });
                    }
                }

                description.appendText("with id: " + idDescription);
            }

            public boolean matchesSafely(View view) {

                this.resources = view.getResources();

                if (childView == null) {
                    RecyclerView recyclerView =
                            (RecyclerView) view.getRootView().findViewById(recyclerViewId);
                    if (recyclerView != null && recyclerView.getId() == recyclerViewId) {
                        childView = recyclerView.getChildAt(position);
                    }
                    else {
                        return false;
                    }
                }

                if (targetViewId == -1) {
                    return view == childView;
                } else {
                    View targetView = childView.findViewById(targetViewId);
                    return view == targetView;
                }

            }
        };
    }

    public static RecyclerViewMatcher withRecyclerView(final int recyclerViewId) {

        return new RecyclerViewMatcher(recyclerViewId);
    }
}

Example usage:

val rv : RecyclerViewMatcher = RecyclerViewMatcher.withRecyclerView(R.id.some_RV_ID)
onView(rv.atPositionOnView(position, R.id.some_view_id)).check(matches(isDisplayed()))