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;
  
  /**
   * Interface for tests to use when they need to be informed of the application lifecycle state.
   *
   * <p>Retrieve instances of the monitor thru ApplicationLifecycleMonitorRegistry.
   *
   * <p>Detecting these lifecycle states requires support from Instrumentation, therefore do not
   * expect an instance to be present under any arbitrary instrumentation.
   */
  public interface ApplicationLifecycleMonitor {
  
    /**
     * Adds a new callback that will be notified when lifecycle changes occur.
     *
     * <p>Implementors will not hold a strong ref to the callback, the code which registers callbacks
     * is responsible for this. Code which registers callbacks should responsibly remove their
     * callback when it is no longer needed.
     *
     * <p>Callbacks may be executed on the main thread of the application, and should take care not to
     * block or otherwise perform expensive operations as it will directly impact the application.
     *
     * @param callback an ApplicationLifecycleCallback
     */
    void addLifecycleCallback(ApplicationLifecycleCallback callback);
  
    /** Removes a previously registered lifecycle callback. */
    void removeLifecycleCallback(ApplicationLifecycleCallback callback);
  }
  