com/android/setupwizardlib/items/ItemHierarchy.java

/*
 * Copyright (C) 2015 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.android.setupwizardlib.items;

/**
 * Representation of zero or more items in a list. Each instance of ItemHierarchy should be capable
 * of being wrapped in ItemAdapter and be displayed.
 *
 * <p>For example, {@link com.android.setupwizardlib.items.Item} is a representation of a single
 * item, typically with data provided from XML. {@link com.android.setupwizardlib.items.ItemGroup}
 * represents a list of child item hierarchies it contains, but itself does not do any display.
 */
public interface ItemHierarchy {

  /**
   * Observer for any changes in this hierarchy. If anything updated that causes this hierarchy to
   * show different content, this observer should be called.
   */
  interface Observer {
    /**
     * Called when an underlying data update that can cause this hierarchy to show different content
     * has occurred.
     *
     * <p>Note: This is a catch-all notification, but recycler view will have a harder time figuring
     * out the animations for the change, and might even not animate the change at all.
     */
    void onChanged(ItemHierarchy itemHierarchy);

    /**
     * Called when an underlying data update that can cause changes that are local to the given
     * items. This method indicates that there are no structural changes like inserting or removing
     * items.
     */
    void onItemRangeChanged(ItemHierarchy itemHierarchy, int positionStart, int itemCount);

    /** Called when items are inserted at the given position. */
    void onItemRangeInserted(ItemHierarchy itemHierarchy, int positionStart, int itemCount);

    /** Called when the given items are moved to a different position. */
    void onItemRangeMoved(
        ItemHierarchy itemHierarchy, int fromPosition, int toPosition, int itemCount);

    /** Called when the given items are removed from the item hierarchy. */
    void onItemRangeRemoved(ItemHierarchy itemHierarchy, int positionStart, int itemCount);
  }

  /** Register an observer to observe changes for this item hierarchy. */
  void registerObserver(Observer observer);

  /** Unregister a previously registered observer. */
  void unregisterObserver(Observer observer);

  /** @return the number of items this item hierarchy represent. */
  int getCount();

  /**
   * Get the item at position.
   *
   * @param position An integer from 0 to {@link #getCount()}}, which indicates the position in this
   *     item hierarchy to get the child item.
   * @return A representation of the item at {@code position}. Must not be {@code null}.
   */
  IItem getItemAt(int position);

  /**
   * Find an item hierarchy within this hierarchy which has the given ID. Or null if no match is
   * found. This hierarchy will be returned if our ID matches. Same restrictions for Android
   * resource IDs apply to this ID. In fact, typically this ID is a resource ID generated from XML.
   *
   * @param id An ID to search for in this item hierarchy.
   * @return An ItemHierarchy which matches the given ID.
   */
  ItemHierarchy findItemById(int id);
}