An Idling resource class for Android Espresso testing that gets the current activity which can then be used to determine idle status. Useful when there are multiple activities.

ActivityCheckIdlingResource.java

import android.app.Activity;
import android.support.test.espresso.IdlingResource;
import android.support.test.espresso.core.deps.guava.collect.Iterables;
import android.support.test.runner.lifecycle.ActivityLifecycleMonitorRegistry;
import android.support.test.runner.lifecycle.Stage;


/**
 * Created by clivejefferies on 13/01/2017.
 *
 * This class can be used to monitor idling resources
 */

public class RequestIdlingResource implements IdlingResource {
    private ResourceCallback resourceCallback;
    private boolean isIdle;

    @Override
    public String getName() {
        return RequestIdlingResource.class.getName();
    }

    @Override
    public boolean isIdleNow() {
        if (isIdle) return true;

        Activity activity = getCurrentActivity();
        if (activity == null) return false;

        idlingCheck(activity);

        if (isIdle) {
            resourceCallback.onTransitionToIdle();
        }
        return isIdle;
    }

    private Activity getCurrentActivity() {
        final Activity[] activity = new Activity[1];
        java.util.Collection<Activity> activities = ActivityLifecycleMonitorRegistry.getInstance().getActivitiesInStage(Stage.RESUMED);
        activity[0] = Iterables.getOnlyElement(activities);
        return activity[0];
    }

    @Override
    public void registerIdleTransitionCallback(
            ResourceCallback resourceCallback) {
        this.resourceCallback = resourceCallback;
    }

    public void idlingCheck(Activity activity)
    {
        /* 
           Look up something (view or method call) on the activity to determine if it is idle or busy
   
         */
    }
}