Initial Contribution

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diff --git a/core/java/android/widget/Adapter.java b/core/java/android/widget/Adapter.java
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+/*
+ * Copyright (C) 2006 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 android.widget;
+
+import android.database.DataSetObserver;
+import android.view.KeyEvent;
+import android.view.View;
+import android.view.ViewGroup;
+
+/**
+ * An Adapter object acts as a bridge between an {@link AdapterView} and the
+ * underlying data for that view. The Adapter provides access to the data items.
+ * The Adapter is also responsible for making a {@link android.view.View} for
+ * each item in the data set.
+ * 
+ * @see android.widget.ArrayAdapter
+ * @see android.widget.CursorAdapter
+ * @see android.widget.SimpleCursorAdapter
+ */
+public interface Adapter {
+    /**
+     * Register an observer that is called when changes happen to the data used by this adapter.
+     *
+     * @param observer the object that gets notified when the data set changes.
+     */
+    void registerDataSetObserver(DataSetObserver observer);
+
+    /**
+     * Unregister an observer that has previously been registered with this
+     * adapter via {@link #registerDataSetObserver}.
+     *
+     * @param observer the object to unregister.
+     */
+    void unregisterDataSetObserver(DataSetObserver observer);
+
+    /**
+     * How many items are in the data set represented by this Adapter.
+     * 
+     * @return Count of items.
+     */
+    int getCount();   
+    
+    /**
+     * Get the data item associated with the specified position in the data set.
+     * 
+     * @param position Position of the item whose data we want within the adapter's 
+     * data set.
+     * @return The data at the specified position.
+     */
+    Object getItem(int position);
+    
+    /**
+     * Get the row id associated with the specified position in the list.
+     * 
+     * @param position The position of the item within the adapter's data set whose row id we want.
+     * @return The id of the item at the specified position.
+     */
+    long getItemId(int position);
+    
+    /**
+     * Indicated whether the item ids are stable across changes to the
+     * underlying data.
+     * 
+     * @return True if the same id always refers to the same object.
+     */
+    boolean hasStableIds();
+    
+    /**
+     * Get a View that displays the data at the specified position in the data set. You can either
+     * create a View manually or inflate it from an XML layout file. When the View is inflated, the
+     * parent View (GridView, ListView...) will apply default layout parameters unless you use
+     * {@link android.view.LayoutInflater#inflate(int, android.view.ViewGroup, boolean)}
+     * to specify a root view and to prevent attachment to the root.
+     * 
+     * @param position The position of the item within the adapter's data set of the item whose view
+     *        we want.
+     * @param convertView The old view to reuse, if possible. Note: You should check that this view
+     *        is non-null and of an appropriate type before using. If it is not possible to convert
+     *        this view to display the correct data, this method can create a new view.
+     * @param parent The parent that this view will eventually be attached to
+     * @return A View corresponding to the data at the specified position.
+     */
+    View getView(int position, View convertView, ViewGroup parent);
+
+    /**
+     * An item view type that causes the {@link AdapterView} to ignore the item
+     * view. For example, this can be used if the client does not want a
+     * particular view to be given for conversion in
+     * {@link #getView(int, View, ViewGroup)}.
+     * 
+     * @see #getItemViewType(int)
+     * @see #getViewTypeCount()
+     */
+    static final int IGNORE_ITEM_VIEW_TYPE = AdapterView.ITEM_VIEW_TYPE_IGNORE;
+    
+    /**
+     * Get the type of View that will be created by {@link #getView} for the specified item.
+     * 
+     * @param position The position of the item within the adapter's data set whose view type we
+     *        want.
+     * @return An integer representing the type of View. Two views should share the same type if one
+     *         can be converted to the other in {@link #getView}. Note: Integers must be in the
+     *         range 0 to {@link #getViewTypeCount} - 1. {@link #IGNORE_ITEM_VIEW_TYPE} can
+     *         also be returned.
+     * @see IGNORE_ITEM_VIEW_TYPE
+     */
+    int getItemViewType(int position);
+    
+    /**
+     * <p>
+     * Returns the number of types of Views that will be created by
+     * {@link #getView}. Each type represents a set of views that can be
+     * converted in {@link #getView}. If the adapter always returns the same
+     * type of View for all items, this method should return 1.
+     * </p>
+     * <p>
+     * This method will only be called when when the adapter is set on the
+     * the {@link AdapterView}.
+     * </p>
+     * 
+     * @return The number of types of Views that will be created by this adapter
+     */
+    int getViewTypeCount();
+    
+    static final int NO_SELECTION = Integer.MIN_VALUE;
+ 
+     /**
+      * @return true if this adapter doesn't contain any data.  This is used to determine
+      * whether the empty view should be displayed.  A typical implementation will return
+      * getCount() == 0 but since getCount() includes the headers and footers, specialized
+      * adapters might want a different behavior.
+      */
+     boolean isEmpty();
+}
+