material-components_material-components-android/lib/java/com/google/android/material/datepicker/PickerFragment.java

/*
 * Copyright 2019 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 com.google.android.material.datepicker;

import androidx.fragment.app.Fragment;
import java.util.LinkedHashSet;

abstract class PickerFragment<S> extends Fragment {

  protected final LinkedHashSet<OnSelectionChangedListener<S>> onSelectionChangedListeners =
      new LinkedHashSet<>();

  abstract DateSelector<S> getDateSelector();

  /** Adds a listener for selection changes. */
  boolean addOnSelectionChangedListener(OnSelectionChangedListener<S> listener) {
    return onSelectionChangedListeners.add(listener);
  }

  /** Removes a listener for selection changes. */
  boolean removeOnSelectionChangedListener(OnSelectionChangedListener<S> listener) {
    return onSelectionChangedListeners.remove(listener);
  }

  /** Removes all listeners for selection changes. */
  void clearOnSelectionChangedListeners() {
    onSelectionChangedListeners.clear();
  }
}