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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.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);
/**
* Indicates 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.
* Heterogeneous lists can specify their number of view types, so that this View is
* always of the right type (see {@link #getViewTypeCount()} and
* {@link #getItemViewType(int)}).
* @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();
}
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