robolectric/src/main/java/org/robolectric/Robolectric.java

package org.robolectric;

import android.app.Activity;
import android.app.Service;
import org.robolectric.shadows.ShadowApplication;
import org.robolectric.util.ActivityController;
import org.robolectric.util.Scheduler;
import org.robolectric.util.ServiceController;
import org.robolectric.internal.ShadowProvider;

import java.util.ServiceLoader;

public class Robolectric {
  private static ShadowsAdapter shadowsAdapter = null;
  private static Iterable<ShadowProvider> providers;

  public static void reset() {
    if (providers == null) {
      providers = ServiceLoader.load(ShadowProvider.class);
    }
    for (ShadowProvider provider : providers) {
      provider.reset();
    }
    RuntimeEnvironment.application = null;
    RuntimeEnvironment.setRobolectricPackageManager(null);
    RuntimeEnvironment.setActivityThread(null);
  }

  public static ShadowsAdapter getShadowsAdapter() {
    synchronized(ShadowsAdapter.class) {
      if(shadowsAdapter == null) {
        try {
          shadowsAdapter = instantiateShadowsAdapter();
        } catch(Throwable t) {
          Throwable cause = t;
          while(cause.getCause() != null) {
            cause = cause.getCause();
          }
          cause.printStackTrace();
        }
      }
    }
    return shadowsAdapter;
  }

  public static <T extends Service> ServiceController<T> buildService(Class<T> serviceClass) {
    return ServiceController.of(getShadowsAdapter(), serviceClass);
  }

  public static <T extends Service> T setupService(Class<T> serviceClass) {
    return ServiceController.of(getShadowsAdapter(), serviceClass).attach().create().get();
  }

  public static <T extends Activity> ActivityController<T> buildActivity(Class<T> activityClass) {
    return ActivityController.of(getShadowsAdapter(), activityClass);
  }

  public static <T extends Activity> T setupActivity(Class<T> activityClass) {
    return ActivityController.of(getShadowsAdapter(), activityClass).setup().get();
  }

  /**
   * Return the foreground scheduler (e.g. the UI thread scheduler).
   *
   * @return  Foreground scheduler.
   */
  public static Scheduler getForegroundThreadScheduler() {
    return ShadowApplication.getInstance().getForegroundThreadScheduler();
  }

  /**
   * Execute all runnables that have been enqueued on the foreground scheduler.
   */
  public static void flushForegroundThreadScheduler() {
    getForegroundThreadScheduler().advanceToLastPostedRunnable();
  }

  /**
   * Return the background scheduler.
   *
   * @return  Background scheduler.
   */
  public static Scheduler getBackgroundThreadScheduler() {
    return ShadowApplication.getInstance().getBackgroundThreadScheduler();
  }

  /**
   * Execute all runnables that have been enqueued on the background scheduler.
   */
  public static void flushBackgroundThreadScheduler() {
    getBackgroundThreadScheduler().advanceToLastPostedRunnable();
  }

  private static ShadowsAdapter instantiateShadowsAdapter() {
    ShadowsAdapter result = null;
    for (ShadowsAdapter adapter : ServiceLoader.load(ShadowsAdapter.class)) {
      if (result == null) {
        result = adapter;
      } else {
        throw new RuntimeException("Multiple " + ShadowsAdapter.class.getCanonicalName() + "s found.  Robolectric has loaded multiple core shadow modules for some reason.");
      }
    }
    if (result == null) {
      throw new RuntimeException("No shadows modules found containing a " + ShadowsAdapter.class.getCanonicalName());
    } else {
      return result;
    }
  }
}