android HeaderViewListAdapter的介紹

public class
HeaderViewListAdapter
extends Object
implements Filterable WrapperListAdapter
Class Overview
ListAdapter used when a ListView has header views. This ListAdapter wraps another one and
also keeps track of the header views and their associated data objects.
This is intended as a base class; you will probably not need to use this class directly in your own code.
HeaderViewListAdapter的主要作用就是在ListAdapter基礎上封裝和升級，為其提供了添加列表頭和列表尾的功能。 該類一般不直接使用，它的主要目的是為我們提供一個對包含列表頭和列表尾的列表進行適配的一個基類。 構造函數如下： Public Constructors HeaderViewListAdapter(ArrayList headerViewInfos, ArrayList footerViewInfos, ListAdapter adapter)
參數
headerViewInfos 用於提供列表頭
footerViewInfos 用於提供列表尾
adapter 用於為列表正文進行適配 另外，ListView.FixedViewInfo其實很簡單，它就是對一個View及其信息的封裝。 Fields public Object data The data backing the view. public boolean isSelectable true if the fixed view should be selectable in the list public View view The view to add to the list Public Constructors ListView.FixedViewInfo() HeaderViewListAdapter源碼如下 HeaderViewListAdapter.java文件 /* * 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;
import java.util.ArrayList;
/** * ListAdapter used when a ListView has header views. This ListAdapter * wraps another one and also keeps track of the header views and their * associated data objects. *

This is intended as a base class; you will probably not need to * use this class directly in your own code. */ public class HeaderViewListAdapter implements WrapperListAdapter, Filterable {
private final ListAdapter mAdapter;
// These two ArrayList are assumed to NOT be null. // They are indeed created when declared in ListView and then shared. ArrayList mHeaderViewInfos; ArrayList mFooterViewInfos;
// Used as a placeholder in case the provided info views are indeed null. // Currently only used by some CTS tests, which may be removed. static final ArrayList EMPTY_INFO_LIST = new ArrayList();
boolean mAreAllFixedViewsSelectable;
private final boolean mIsFilterable;
public HeaderViewListAdapter(ArrayList headerViewInfos, ArrayList footerViewInfos, ListAdapter adapter) { mAdapter = adapter; mIsFilterable = adapter instanceof Filterable;
if (headerViewInfos == null) { mHeaderViewInfos = EMPTY_INFO_LIST; } else { mHeaderViewInfos = headerViewInfos; }
if (footerViewInfos == null) { mFooterViewInfos = EMPTY_INFO_LIST; } else { mFooterViewInfos = footerViewInfos; }
mAreAllFixedViewsSelectable = areAllListInfosSelectable(mHeaderViewInfos) && areAllListInfosSelectable(mFooterViewInfos); }
public int getHeadersCount() { return mHeaderViewInfos.size(); }
public int getFootersCount() { return mFooterViewInfos.size(); }
public boolean isEmpty() { return mAdapter == null || mAdapter.isEmpty(); }
private boolean areAllListInfosSelectable(ArrayList infos) { if (infos != null) { for (ListView.FixedViewInfo info : infos) { if (!info.isSelectable) { return false; } } } return true; }
public boolean removeHeader(View v) { for (int i = 0; i < mHeaderViewInfos.size(); i++) { ListView.FixedViewInfo info = mHeaderViewInfos.get(i); if (info.view == v) { mHeaderViewInfos.remove(i);
mAreAllFixedViewsSelectable = areAllListInfosSelectable(mHeaderViewInfos) && areAllListInfosSelectable(mFooterViewInfos);
return true; } }
return false; }
public boolean removeFooter(View v) { for (int i = 0; i < mFooterViewInfos.size(); i++) { ListView.FixedViewInfo info = mFooterViewInfos.get(i); if (info.view == v) { mFooterViewInfos.remove(i);
mAreAllFixedViewsSelectable = areAllListInfosSelectable(mHeaderViewInfos) && areAllListInfosSelectable(mFooterViewInfos);
return true; } }
return false; }
public int getCount() { if (mAdapter != null) { return getFootersCount() + getHeadersCount() + mAdapter.getCount(); } else { return getFootersCount() + getHeadersCount(); } }
public boolean areAllItemsEnabled() { if (mAdapter != null) { return mAreAllFixedViewsSelectable && mAdapter.areAllItemsEnabled(); } else { return true; } }
public boolean isEnabled(int position) { // Header (negative positions will throw an ArrayIndexOutOfBoundsException) int numHeaders = getHeadersCount(); if (position < numHeaders) { return mHeaderViewInfos.get(position).isSelectable; }
// Adapter final int adjPosition = position - numHeaders; int adapterCount = 0; if (mAdapter != null) { adapterCount = mAdapter.getCount(); if (adjPosition < adapterCount) { return mAdapter.isEnabled(adjPosition); } }
// Footer (off-limits positions will throw an ArrayIndexOutOfBoundsException) return mFooterViewInfos.get(adjPosition - adapterCount).isSelectable; }
public Object getItem(int position) { // Header (negative positions will throw an ArrayIndexOutOfBoundsException) int numHeaders = getHeadersCount(); if (position < numHeaders) { return mHeaderViewInfos.get(position).data; }
// Adapter final int adjPosition = position - numHeaders; int adapterCount = 0; if (mAdapter != null) { adapterCount = mAdapter.getCount(); if (adjPosition < adapterCount) { return mAdapter.getItem(adjPosition); } }
// Footer (off-limits positions will throw an ArrayIndexOutOfBoundsException) return mFooterViewInfos.get(adjPosition - adapterCount).data; }
public long getItemId(int position) { int numHeaders = getHeadersCount(); if (mAdapter != null && position >= numHeaders) { int adjPosition = position - numHeaders; int adapterCount = mAdapter.getCount(); if (adjPosition < adapterCount) { return mAdapter.getItemId(adjPosition); } } return -1; }
public boolean hasStableIds() { if (mAdapter != null) { return mAdapter.hasStableIds(); } return false; }
public View getView(int position, View convertView, ViewGroup parent) { // Header (negative positions will throw an ArrayIndexOutOfBoundsException) int numHeaders = getHeadersCount(); if (position < numHeaders) { return mHeaderViewInfos.get(position).view; }
// Adapter final int adjPosition = position - numHeaders; int adapterCount = 0; if (mAdapter != null) { adapterCount = mAdapter.getCount(); if (adjPosition < adapterCount) { return mAdapter.getView(adjPosition, convertView, parent); } }
// Footer (off-limits positions will throw an ArrayIndexOutOfBoundsException) return mFooterViewInfos.get(adjPosition - adapterCount).view; }
public int getItemViewType(int position) { int numHeaders = getHeadersCount(); if (mAdapter != null && position >= numHeaders) { int adjPosition = position - numHeaders; int adapterCount = mAdapter.getCount(); if (adjPosition < adapterCount) { return mAdapter.getItemViewType(adjPosition); } }
return AdapterView.ITEM_VIEW_TYPE_HEADER_OR_FOOTER; }
public int getViewTypeCount() { if (mAdapter != null) { return mAdapter.getViewTypeCount(); } return 1; }
public void registerDataSetObserver(DataSetObserver observer) { if (mAdapter != null) { mAdapter.registerDataSetObserver(observer); } }
public void unregisterDataSetObserver(DataSetObserver observer) { if (mAdapter != null) { mAdapter.unregisterDataSetObserver(observer); } }
public Filter getFilter() { if (mIsFilterable) { return ((Filterable) mAdapter).getFilter(); } return null; } public ListAdapter getWrappedAdapter() { return mAdapter; } }