content: /*
   * Copyright (C) 2014 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package androidx.test.runner.lifecycle;
  
  import java.util.concurrent.atomic.AtomicReference;
  
  /**
   * An exposed registry instance to make it easy for callers to find the lifecycle monitor for their
   * application.
   */
  public final class ActivityLifecycleMonitorRegistry {
  
    private static final AtomicReference<ActivityLifecycleMonitor> lifecycleMonitor =
        new AtomicReference<ActivityLifecycleMonitor>(null);
  
    // singleton - disallow creation
    private ActivityLifecycleMonitorRegistry() {}
  
    /**
     * Returns the ActivityLifecycleMonitor.
     *
     * <p>This monitor is not guaranteed to be present under all instrumentations.
     *
     * @return ActivityLifecycleMonitor the monitor for this application.
     * @throws IllegalStateException if no monitor has been registered.
     */
    public static ActivityLifecycleMonitor getInstance() {
      ActivityLifecycleMonitor instance = lifecycleMonitor.get();
      if (null == instance) {
        throw new IllegalStateException(
            "No lifecycle monitor registered! Are you running "
                + "under an Instrumentation which registers lifecycle monitors?");
      }
      return instance;
    }
  
    /**
     * Stores a lifecycle monitor in the registry.
     *
     * <p>This is a global registry - so be aware of the impact of calling this method!
     *
     * @param monitor the monitor for this application. Null deregisters any existing monitor.
     */
    public static void registerInstance(ActivityLifecycleMonitor monitor) {
      lifecycleMonitor.set(monitor);
    }
  }
  