1 /*
2  * Copyright (C) 2015 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.setupwizardlib.items;
18 
19 /**
20  * Representation of zero or more items in a list. Each instance of ItemHierarchy should be capable
21  * of being wrapped in ItemAdapter and be displayed.
22  *
23  * For example, {@link com.android.setupwizardlib.items.Item} is a representation of a single item,
24  * typically with data provided from XML. {@link com.android.setupwizardlib.items.ItemGroup}
25  * represents a list of child item hierarchies it contains, but itself does not do any display.
26  */
27 public interface ItemHierarchy {
28 
29     /**
30      * Observer for any changes in this hierarchy. If anything updated that causes this hierarchy to
31      * show different content, this observer should be called.
32      */
33     interface Observer {
34         /**
35          * Called when an underlying data update that can cause this hierarchy to show different
36          * content has occurred.
37          *
38          * <p>Note: This is a catch-all notification, but recycler view will have a harder time
39          * figuring out the animations for the change, and might even not animate the change at all.
40          */
onChanged(ItemHierarchy itemHierarchy)41         void onChanged(ItemHierarchy itemHierarchy);
42 
43         /**
44          * Called when an underlying data update that can cause changes that are local to the given
45          * items. This method indicates that there are no structural changes like inserting or
46          * removing items.
47          */
onItemRangeChanged(ItemHierarchy itemHierarchy, int positionStart, int itemCount)48         void onItemRangeChanged(ItemHierarchy itemHierarchy, int positionStart, int itemCount);
49 
50         /**
51          * Called when items are inserted at the given position.
52          */
onItemRangeInserted(ItemHierarchy itemHierarchy, int positionStart, int itemCount)53         void onItemRangeInserted(ItemHierarchy itemHierarchy, int positionStart, int itemCount);
54 
55         /**
56          * Called when the given items are moved to a different position.
57          */
onItemRangeMoved(ItemHierarchy itemHierarchy, int fromPosition, int toPosition, int itemCount)58         void onItemRangeMoved(ItemHierarchy itemHierarchy, int fromPosition, int toPosition,
59                 int itemCount);
60 
61         /**
62          * Called when the given items are removed from the item hierarchy.
63          */
onItemRangeRemoved(ItemHierarchy itemHierarchy, int positionStart, int itemCount)64         void onItemRangeRemoved(ItemHierarchy itemHierarchy, int positionStart, int itemCount);
65     }
66 
67     /**
68      * Register an observer to observe changes for this item hierarchy.
69      */
registerObserver(Observer observer)70     void registerObserver(Observer observer);
71 
72     /**
73      * Unregister a previously registered observer.
74      */
unregisterObserver(Observer observer)75     void unregisterObserver(Observer observer);
76 
77     /**
78      * @return the number of items this item hierarchy represent.
79      */
getCount()80     int getCount();
81 
82     /**
83      * Get the item at position.
84      *
85      * @param position An integer from 0 to {@link #getCount()}}, which indicates the position in
86      *                 this item hierarchy to get the child item.
87      * @return A representation of the item at {@code position}. Must not be {@code null}.
88      */
getItemAt(int position)89     IItem getItemAt(int position);
90 
91     /**
92      * Find an item hierarchy within this hierarchy which has the given ID. Or null if no match is
93      * found. This hierarchy will be returned if our ID matches. Same restrictions for Android
94      * resource IDs apply to this ID. In fact, typically this ID is a resource ID generated from
95      * XML.
96      *
97      * @param id An ID to search for in this item hierarchy.
98      * @return An ItemHierarchy which matches the given ID.
99      */
findItemById(int id)100     ItemHierarchy findItemById(int id);
101 }
102