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darnmason/HeaderViewRecyclerAdapter.java

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  1. darnmason renamed this gist Nov 10, 2014. 1 changed file with 0 additions and 0 deletions.
    0 HeaderViewRecyclerAdapter → HeaderViewRecyclerAdapter.java
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    File renamed without changes.
  2. darnmason created this gist Nov 10, 2014.
    208 changes: 208 additions & 0 deletions HeaderViewRecyclerAdapter
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    Original file line number Diff line number Diff line change
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    /*
    * Copyright (C) 2014 darnmason
    *
    * 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.
    */

    import android.support.v7.widget.RecyclerView;
    import android.view.View;
    import android.view.ViewGroup;

    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;

    /**
    * <p>
    * RecyclerView adapter designed to wrap an existing adapter allowing the addition of
    * header views and footer views.
    * </p>
    * <p>
    * I implemented it to aid with the transition from ListView to RecyclerView where the ListView's
    * addHeaderView and addFooterView methods were used. Using this class you may initialize your
    * header views in the Fragment/Activity and add them to the adapter in the same way you used to
    * add them to a ListView.
    * </p>
    * <p>
    * I also required to be able to swap out multiple adapters with different content, therefore
    * setAdapter may be called multiple times.
    * </p>
    * Created by darnmason on 07/11/2014.
    */
    public class HeaderViewRecyclerAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private static final int HEADERS_START = Integer.MIN_VALUE;
    private static final int FOOTERS_START = Integer.MIN_VALUE + 10;
    private static final int ITEMS_START = Integer.MIN_VALUE + 20;
    private static final int ADAPTER_MAX_TYPES = 100;

    private RecyclerView.Adapter mWrappedAdapter;
    private List<View> mHeaderViews, mFooterViews;
    private Map<Class, Integer> mItemTypesOffset;

    /**
    * Construct a new header view recycler adapter
    * @param adapter The underlying adapter to wrap
    */
    public HeaderViewRecyclerAdapter(RecyclerView.Adapter adapter) {
    mHeaderViews = new ArrayList<View>();
    mFooterViews = new ArrayList<View>();
    mItemTypesOffset = new HashMap<Class, Integer>();
    setWrappedAdapter(adapter);
    }

    /**
    * Replaces the underlying adapter, notifying RecyclerView of changes
    * @param adapter The new adapter to wrap
    */
    public void setAdapter(RecyclerView.Adapter adapter) {
    if(mWrappedAdapter != null && mWrappedAdapter.getItemCount() > 0) {
    notifyItemRangeRemoved(getHeaderCount(), mWrappedAdapter.getItemCount());
    }
    setWrappedAdapter(adapter);
    notifyItemRangeInserted(getHeaderCount(), mWrappedAdapter.getItemCount());
    }

    @Override
    public int getItemViewType(int position) {
    int hCount = getHeaderCount();
    if (position < hCount) return HEADERS_START + position;
    else {
    int itemCount = mWrappedAdapter.getItemCount();
    if (position < hCount + itemCount) {
    return getAdapterTypeOffset() + mWrappedAdapter.getItemViewType(position - hCount);
    }
    else return FOOTERS_START + position - hCount - itemCount;
    }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
    if (viewType < HEADERS_START + getHeaderCount())
    return new StaticViewHolder(mHeaderViews.get(viewType - HEADERS_START));
    else if (viewType < FOOTERS_START + getFooterCount())
    return new StaticViewHolder(mFooterViews.get(viewType - FOOTERS_START));
    else {
    return mWrappedAdapter.onCreateViewHolder(viewGroup, viewType - getAdapterTypeOffset());
    }
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
    int hCount = getHeaderCount();
    if (position >= hCount && position < hCount + mWrappedAdapter.getItemCount())
    mWrappedAdapter.onBindViewHolder(viewHolder, position - hCount);
    }

    /**
    * Add a static view to appear at the start of the RecyclerView. Headers are displayed in the
    * order they were added.
    * @param view The header view to add
    */
    public void addHeaderView(View view) {
    mHeaderViews.add(view);
    }

    /**
    * Add a static view to appear at the end of the RecyclerView. Footers are displayed in the
    * order they were added.
    * @param view The footer view to add
    */
    public void addFooterView(View view) {
    mFooterViews.add(view);
    }

    @Override
    public int getItemCount() {
    return getHeaderCount() + getFooterCount() + getWrappedItemCount();
    }

    /**
    * @return The item count in the underlying adapter
    */
    public int getWrappedItemCount() {
    return mWrappedAdapter.getItemCount();
    }

    /**
    * @return The number of header views added
    */
    public int getHeaderCount() {
    return mHeaderViews.size();
    }

    /**
    * @return The number of footer views added
    */
    public int getFooterCount() {
    return mFooterViews.size();
    }

    private void setWrappedAdapter(RecyclerView.Adapter adapter) {
    if (mWrappedAdapter != null) mWrappedAdapter.unregisterAdapterDataObserver(mDataObserver);
    mWrappedAdapter = adapter;
    Class adapterClass = mWrappedAdapter.getClass();
    if(!mItemTypesOffset.containsKey(adapterClass)) putAdapterTypeOffset(adapterClass);
    mWrappedAdapter.registerAdapterDataObserver(mDataObserver);
    }

    private void putAdapterTypeOffset(Class adapterClass) {
    mItemTypesOffset.put(adapterClass, ITEMS_START + mItemTypesOffset.size() * ADAPTER_MAX_TYPES);
    }

    private int getAdapterTypeOffset() {
    return mItemTypesOffset.get(mWrappedAdapter.getClass());
    }

    private RecyclerView.AdapterDataObserver mDataObserver = new RecyclerView.AdapterDataObserver() {
    @Override
    public void onChanged() {
    super.onChanged();
    notifyDataSetChanged();
    }

    @Override
    public void onItemRangeChanged(int positionStart, int itemCount) {
    super.onItemRangeChanged(positionStart, itemCount);
    notifyItemRangeChanged(positionStart + getHeaderCount(), itemCount);
    }

    @Override
    public void onItemRangeInserted(int positionStart, int itemCount) {
    super.onItemRangeInserted(positionStart, itemCount);
    notifyItemRangeInserted(positionStart + getHeaderCount(), itemCount);
    }

    @Override
    public void onItemRangeRemoved(int positionStart, int itemCount) {
    super.onItemRangeRemoved(positionStart, itemCount);
    notifyItemRangeRemoved(positionStart + getHeaderCount(), itemCount);
    }

    @Override
    public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
    super.onItemRangeMoved(fromPosition, toPosition, itemCount);
    int hCount = getHeaderCount();
    // TODO: No notifyItemRangeMoved method?
    notifyItemRangeChanged(fromPosition + hCount, toPosition + hCount + itemCount);
    }
    };

    private static class StaticViewHolder extends RecyclerView.ViewHolder {

    public StaticViewHolder(View itemView) {
    super(itemView);
    }
    }
    }