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.database.DataSetObserver; 20 import android.view.View; 21 import android.view.ViewGroup; 22 23 /** 24 * An Adapter object acts as a bridge between an {@link AdapterView} and the 25 * underlying data for that view. The Adapter provides access to the data items. 26 * The Adapter is also responsible for making a {@link android.view.View} for 27 * each item in the data set. 28 * 29 * @see android.widget.ArrayAdapter 30 * @see android.widget.CursorAdapter 31 * @see android.widget.SimpleCursorAdapter 32 */ 33 public interface Adapter { 34 /** 35 * Register an observer that is called when changes happen to the data used by this adapter. 36 * 37 * @param observer the object that gets notified when the data set changes. 38 */ 39 void registerDataSetObserver(DataSetObserver observer); 40 41 /** 42 * Unregister an observer that has previously been registered with this 43 * adapter via {@link #registerDataSetObserver}. 44 * 45 * @param observer the object to unregister. 46 */ 47 void unregisterDataSetObserver(DataSetObserver observer); 48 49 /** 50 * How many items are in the data set represented by this Adapter. 51 * 52 * @return Count of items. 53 */ 54 int getCount(); 55 56 /** 57 * Get the data item associated with the specified position in the data set. 58 * 59 * @param position Position of the item whose data we want within the adapter's 60 * data set. 61 * @return The data at the specified position. 62 */ 63 Object getItem(int position); 64 65 /** 66 * Get the row id associated with the specified position in the list. 67 * 68 * @param position The position of the item within the adapter's data set whose row id we want. 69 * @return The id of the item at the specified position. 70 */ 71 long getItemId(int position); 72 73 /** 74 * Indicates whether the item ids are stable across changes to the 75 * underlying data. 76 * 77 * @return True if the same id always refers to the same object. 78 */ 79 boolean hasStableIds(); 80 81 /** 82 * Get a View that displays the data at the specified position in the data set. You can either 83 * create a View manually or inflate it from an XML layout file. When the View is inflated, the 84 * parent View (GridView, ListView...) will apply default layout parameters unless you use 85 * {@link android.view.LayoutInflater#inflate(int, android.view.ViewGroup, boolean)} 86 * to specify a root view and to prevent attachment to the root. 87 * 88 * @param position The position of the item within the adapter's data set of the item whose view 89 * we want. 90 * @param convertView The old view to reuse, if possible. Note: You should check that this view 91 * is non-null and of an appropriate type before using. If it is not possible to convert 92 * this view to display the correct data, this method can create a new view. 93 * Heterogeneous lists can specify their number of view types, so that this View is 94 * always of the right type (see {@link #getViewTypeCount()} and 95 * {@link #getItemViewType(int)}). 96 * @param parent The parent that this view will eventually be attached to 97 * @return A View corresponding to the data at the specified position. 98 */ 99 View getView(int position, View convertView, ViewGroup parent); 100 101 /** 102 * An item view type that causes the {@link AdapterView} to ignore the item 103 * view. For example, this can be used if the client does not want a 104 * particular view to be given for conversion in 105 * {@link #getView(int, View, ViewGroup)}. 106 * 107 * @see #getItemViewType(int) 108 * @see #getViewTypeCount() 109 */ 110 static final int IGNORE_ITEM_VIEW_TYPE = AdapterView.ITEM_VIEW_TYPE_IGNORE; 111 112 /** 113 * Get the type of View that will be created by {@link #getView} for the specified item. 114 * 115 * @param position The position of the item within the adapter's data set whose view type we 116 * want. 117 * @return An integer representing the type of View. Two views should share the same type if one 118 * can be converted to the other in {@link #getView}. Note: Integers must be in the 119 * range 0 to {@link #getViewTypeCount} - 1. {@link #IGNORE_ITEM_VIEW_TYPE} can 120 * also be returned. 121 * @see #IGNORE_ITEM_VIEW_TYPE 122 */ 123 int getItemViewType(int position); 124 125 /** 126 * <p> 127 * Returns the number of types of Views that will be created by 128 * {@link #getView}. Each type represents a set of views that can be 129 * converted in {@link #getView}. If the adapter always returns the same 130 * type of View for all items, this method should return 1. 131 * </p> 132 * <p> 133 * This method will only be called when when the adapter is set on the 134 * the {@link AdapterView}. 135 * </p> 136 * 137 * @return The number of types of Views that will be created by this adapter 138 */ 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 */ 149 boolean isEmpty(); 150 } 151 152
