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1 /*
2  * Copyright (C) 2006 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 android.widget;
18 
19 import android.annotation.Nullable;
20 import android.database.DataSetObserver;
21 import android.view.View;
22 import android.view.ViewGroup;
23 
24 /**
25  * An Adapter object acts as a bridge between an {@link AdapterView} and the
26  * underlying data for that view. The Adapter provides access to the data items.
27  * The Adapter is also responsible for making a {@link android.view.View} for
28  * each item in the data set.
29  *
30  * @see android.widget.ArrayAdapter
31  * @see android.widget.CursorAdapter
32  * @see android.widget.SimpleCursorAdapter
33  */
34 public interface Adapter {
35     /**
36      * Register an observer that is called when changes happen to the data used by this adapter.
37      *
38      * @param observer the object that gets notified when the data set changes.
39      */
registerDataSetObserver(DataSetObserver observer)40     void registerDataSetObserver(DataSetObserver observer);
41 
42     /**
43      * Unregister an observer that has previously been registered with this
44      * adapter via {@link #registerDataSetObserver}.
45      *
46      * @param observer the object to unregister.
47      */
unregisterDataSetObserver(DataSetObserver observer)48     void unregisterDataSetObserver(DataSetObserver observer);
49 
50     /**
51      * How many items are in the data set represented by this Adapter.
52      *
53      * @return Count of items.
54      */
getCount()55     int getCount();
56 
57     /**
58      * Get the data item associated with the specified position in the data set.
59      *
60      * @param position Position of the item whose data we want within the adapter's
61      * data set.
62      * @return The data at the specified position.
63      */
getItem(int position)64     Object getItem(int position);
65 
66     /**
67      * Get the row id associated with the specified position in the list.
68      *
69      * @param position The position of the item within the adapter's data set whose row id we want.
70      * @return The id of the item at the specified position.
71      */
getItemId(int position)72     long getItemId(int position);
73 
74     /**
75      * Indicates whether the item ids are stable across changes to the
76      * underlying data.
77      *
78      * @return True if the same id always refers to the same object.
79      */
hasStableIds()80     boolean hasStableIds();
81 
82     /**
83      * Get a View that displays the data at the specified position in the data set. You can either
84      * create a View manually or inflate it from an XML layout file. When the View is inflated, the
85      * parent View (GridView, ListView...) will apply default layout parameters unless you use
86      * {@link android.view.LayoutInflater#inflate(int, android.view.ViewGroup, boolean)}
87      * to specify a root view and to prevent attachment to the root.
88      *
89      * @param position The position of the item within the adapter's data set of the item whose view
90      *        we want.
91      * @param convertView The old view to reuse, if possible. Note: You should check that this view
92      *        is non-null and of an appropriate type before using. If it is not possible to convert
93      *        this view to display the correct data, this method can create a new view.
94      *        Heterogeneous lists can specify their number of view types, so that this View is
95      *        always of the right type (see {@link #getViewTypeCount()} and
96      *        {@link #getItemViewType(int)}).
97      * @param parent The parent that this view will eventually be attached to
98      * @return A View corresponding to the data at the specified position.
99      */
getView(int position, View convertView, ViewGroup parent)100     View getView(int position, View convertView, ViewGroup parent);
101 
102     /**
103      * An item view type that causes the {@link AdapterView} to ignore the item
104      * view. For example, this can be used if the client does not want a
105      * particular view to be given for conversion in
106      * {@link #getView(int, View, ViewGroup)}.
107      *
108      * @see #getItemViewType(int)
109      * @see #getViewTypeCount()
110      */
111     static final int IGNORE_ITEM_VIEW_TYPE = AdapterView.ITEM_VIEW_TYPE_IGNORE;
112 
113     /**
114      * Get the type of View that will be created by {@link #getView} for the specified item.
115      *
116      * @param position The position of the item within the adapter's data set whose view type we
117      *        want.
118      * @return An integer representing the type of View. Two views should share the same type if one
119      *         can be converted to the other in {@link #getView}. Note: Integers must be in the
120      *         range 0 to {@link #getViewTypeCount} - 1. {@link #IGNORE_ITEM_VIEW_TYPE} can
121      *         also be returned.
122      * @see #IGNORE_ITEM_VIEW_TYPE
123      */
getItemViewType(int position)124     int getItemViewType(int position);
125 
126     /**
127      * <p>
128      * Returns the number of types of Views that will be created by
129      * {@link #getView}. Each type represents a set of views that can be
130      * converted in {@link #getView}. If the adapter always returns the same
131      * type of View for all items, this method should return 1.
132      * </p>
133      * <p>
134      * This method will only be called when the adapter is set on the {@link AdapterView}.
135      * </p>
136      *
137      * @return The number of types of Views that will be created by this adapter
138      */
getViewTypeCount()139     int getViewTypeCount();
140 
141     static final int NO_SELECTION = Integer.MIN_VALUE;
142 
143      /**
144       * @return true if this adapter doesn't contain any data.  This is used to determine
145       * whether the empty view should be displayed.  A typical implementation will return
146       * getCount() == 0 but since getCount() includes the headers and footers, specialized
147       * adapters might want a different behavior.
148       */
isEmpty()149      boolean isEmpty();
150 
151     /**
152      * Gets a string representation of the adapter data that can help
153      * {@link android.service.autofill.AutofillService} autofill the view backed by the adapter.
154      *
155      * <p>
156      * It should only be set (i.e., non-{@code null} if the values do not represent PII
157      * (Personally Identifiable Information - sensitive data such as email addresses,
158      * credit card numbers, passwords, etc...). For
159      * example, it's ok to return a list of month names, but not a list of usernames. A good rule of
160      * thumb is that if the adapter data comes from static resources, such data is not PII - see
161      * {@link android.view.ViewStructure#setDataIsSensitive(boolean)} for more info.
162      *
163      * @return {@code null} by default, unless implementations override it.
164      */
getAutofillOptions()165     default @Nullable CharSequence[] getAutofillOptions() {
166         return null;
167     }
168 }
169