content: /*
   * Copyright (C) 2017 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.internal.runner.lifecycle;
  
  import static androidx.test.internal.util.Checks.checkNotNull;
  
  import android.app.Application;
  import android.util.Log;
  import androidx.annotation.RestrictTo;
  import androidx.test.runner.lifecycle.ApplicationLifecycleCallback;
  import androidx.test.runner.lifecycle.ApplicationLifecycleMonitor;
  import androidx.test.runner.lifecycle.ApplicationStage;
  import java.lang.ref.WeakReference;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  /**
   * Implementation of a ApplicationLifecycleMonitor
   *
   * @hide
   */
  @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP) // used by robolectric
  public class ApplicationLifecycleMonitorImpl implements ApplicationLifecycleMonitor {
  
    private static final String TAG = "ApplicationLifecycleMonitorImpl";
  
    // Accessed from any thread.
    private final List<WeakReference<ApplicationLifecycleCallback>> callbacks = new ArrayList<>();
  
    @Override
    public void addLifecycleCallback(ApplicationLifecycleCallback callback) {
      // there will never be too many callbacks, so iterating over a list will probably
      // be faster then the constant time costs of setting up and maintaining a map.
      checkNotNull(callback);
  
      synchronized (callbacks) {
        boolean needsAdd = true;
        Iterator<WeakReference<ApplicationLifecycleCallback>> refIter = callbacks.iterator();
        while (refIter.hasNext()) {
          ApplicationLifecycleCallback storedCallback = refIter.next().get();
          if (null == storedCallback) {
            refIter.remove();
          } else if (storedCallback == callback) {
            needsAdd = false;
          }
        }
        if (needsAdd) {
          callbacks.add(new WeakReference<>(callback));
        }
      }
    }
  
    @Override
    public void removeLifecycleCallback(ApplicationLifecycleCallback callback) {
      checkNotNull(callback);
  
      synchronized (callbacks) {
        Iterator<WeakReference<ApplicationLifecycleCallback>> refIter = callbacks.iterator();
        while (refIter.hasNext()) {
          ApplicationLifecycleCallback storedCallback = refIter.next().get();
          if (null == storedCallback) {
            refIter.remove();
          } else if (storedCallback == callback) {
            refIter.remove();
          }
        }
      }
    }
  
    public void signalLifecycleChange(Application app, ApplicationStage stage) {
      synchronized (callbacks) {
        Iterator<WeakReference<ApplicationLifecycleCallback>> refIter = callbacks.iterator();
        while (refIter.hasNext()) {
          ApplicationLifecycleCallback callback = refIter.next().get();
          if (null == callback) {
            refIter.remove();
          } else {
            try {
              callback.onApplicationLifecycleChanged(app, stage);
            } catch (RuntimeException re) {
              Log.e(
                  TAG,
                  String.format(
                      "Callback threw exception! (callback: %s stage: %s)", callback, stage),
                  re);
            }
          }
        }
      }
    }
  }
  