content: /*
   *  Copyright 2017 Google Inc.
   *
   *  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 mobi.maptrek.util;
  
  import android.util.Log;
  
  import androidx.annotation.MainThread;
  import androidx.annotation.NonNull;
  import androidx.annotation.Nullable;
  import androidx.lifecycle.LifecycleOwner;
  import androidx.lifecycle.MutableLiveData;
  import androidx.lifecycle.Observer;
  
  import java.util.concurrent.atomic.AtomicBoolean;
  
  /**
   * A lifecycle-aware observable that sends only new updates after subscription, used for events like
   * navigation and Snackbar messages.
   * <p>
   * This avoids a common problem with events: on configuration change (like rotation) an update
   * can be emitted if the observer is active. This LiveData only calls the observable if there's an
   * explicit call to setValue() or call().
   * <p>
   * Note that only one observer is going to be notified of changes.
   */
  public class SingleLiveEvent<T> extends MutableLiveData<T> {
  
      private static final String TAG = "SingleLiveEvent";
  
      private final AtomicBoolean mPending = new AtomicBoolean(false);
  
      @MainThread
      public void observe(@NonNull LifecycleOwner owner, @NonNull Observer<? super T> observer) {
          if (hasActiveObservers()) {
              Log.w(TAG, "Multiple observers registered but only one will be notified of changes.");
          }
          // Observe the internal MutableLiveData
          super.observe(owner, t -> {
              if (mPending.compareAndSet(true, false)) {
                  observer.onChanged(t);
              }
          });
      }
  
      @MainThread
      public void setValue(@Nullable T value) {
          mPending.set(true);
          super.setValue(value);
      }
  
      /**
       * Used for cases where T is Void, to make calls cleaner.
       */
      @MainThread
      public void call() {
          setValue(null);
      }
  }
  