打造自己的RecyclerView适配器和可添加头部尾部的RecyclerView

打造自己的RecyclerView通用适配器，使用更方便

创建多布局支持接口MultiTypeSupport

public interface MultiTypeSupport<T> {
    /**
     * 根据当前位置或者条目数据返回布局
     *
     * @param item T
     * @param position int
     * @return int
     */
    int getLayoutId(T item, int position);
}

创建Adapter条目的点击事件接口

public interface OnItemClickListener {
    /**
     * 点击
     * @param position int
     */
    void onItemClick(int position);
}

创建Adapter条目的长按事件接口

public interface OnItemLongClickListener {
    /**
     * 长按
     *
     * @param position i
     * @return b
     */
    boolean onLongClick(int position);
}

创建RecyclerView的ViewHolder

public class ViewHolder extends RecyclerView.ViewHolder {

    /**
     * 用来存放子View减少findViewById的次数
     */
    private final SparseArray<View> mViews;

    public ViewHolder(View itemView) {
        super(itemView);
        mViews = new SparseArray<>();
    }

    /**
     * 设置TextView文本
     */
    public ViewHolder setText(int viewId, CharSequence text) {
        TextView tv = getView(viewId);
        tv.setText(text);
        return this;
    }

    /**
     * 通过id获取view
     */
    public <T extends View> T getView(int viewId) {
        // 先从缓存中找
        View view = mViews.get(viewId);
        if (view == null) {
            // 直接从ItemView中找
            view = itemView.findViewById(viewId);
            mViews.put(viewId, view);
        }
        return (T) view;
    }

    /**
     * 设置View的Visibility
     */
    public ViewHolder setViewVisibility(int viewId, int visibility) {
        getView(viewId).setVisibility(visibility);
        return this;
    }

    /**
     * 设置ImageView的资源
     */
    public ViewHolder setImageResource(int viewId, int resourceId) {
        ImageView imageView = getView(viewId);
        imageView.setImageResource(resourceId);
        return this;
    }

    /**
     * 设置条目点击事件
     */
    public void setOnItemClickListener(View.OnClickListener listener) {
        itemView.setOnClickListener(listener);
    }

    /**
     * 设置条目长按事件
     */
    public void setOnItemLongClickListener(View.OnLongClickListener listener) {
        itemView.setOnLongClickListener(listener);
    }

    /**
     * 设置图片通过路径,这里稍微处理得复杂一些，因为考虑加载图片的第三方可能不太一样
     * 也可以直接写死
     */
    public ViewHolder setImageByUrl(int viewId, HolderImageLoader imageLoader) {
        ImageView imageView = getView(viewId);
        if (imageLoader == null) {
            throw new NullPointerException("imageLoader is null!");
        }
        imageLoader.displayImage(imageView.getContext(), imageView, imageLoader.getImagePath());
        return this;
    }

    /**
     * 图片加载，这里稍微处理得复杂一些，因为考虑加载图片的第三方可能不太一样
     * 也可以不写这个类
     */
    public static abstract class HolderImageLoader {
        private final String mImagePath;

        public HolderImageLoader(String imagePath) {
            this.mImagePath = imagePath;
        }

        public String getImagePath() {
            return mImagePath;
        }

        public abstract void displayImage(Context context, ImageView imageView, String imagePath);
    }
}

创建通用的Adapter

public abstract class BaseRecyclerAdapter<T> extends RecyclerView.Adapter<ViewHolder> {

    protected Context mContext;
    protected LayoutInflater mInflater;
    /**
     * 数据怎么办？
     */
    protected List<T> mData;
    /**
     * 布局怎么办？
     */
    private int mLayoutId;

    // 多布局支持
    private MultiTypeSupport mMultiTypeSupport;

    public BaseRecyclerAdapter(Context context, List<T> data, int layoutId) {
        this.mContext = context;
        this.mInflater = LayoutInflater.from(mContext);
        this.mData = data;
        this.mLayoutId = layoutId;
    }

    /**
     * 多布局支持
     */
    public BaseRecyclerAdapter(Context context, List<T> data, MultiTypeSupport<T> multiTypeSupport) {
        this(context, data, -1);
        this.mMultiTypeSupport = multiTypeSupport;
    }

    /**
     * 根据当前位置获取不同的viewType
     */
    @Override
    public int getItemViewType(int position) {
        // 多布局支持
        if (mMultiTypeSupport != null) {
            return mMultiTypeSupport.getLayoutId(mData.get(position), position);
        }
        return super.getItemViewType(position);
    }

    @NotNull
    @Override
    public ViewHolder onCreateViewHolder(@NotNull ViewGroup parent, int viewType) {
        // 多布局支持
        if (mMultiTypeSupport != null) {
            mLayoutId = viewType;
        }
        // 先inflate数据
        View itemView = mInflater.inflate(mLayoutId, parent, false);
        // 返回ViewHolder
        return new ViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NotNull final ViewHolder holder, final int position) {
        // 设置点击和长按事件
        if (mItemClickListener != null) {
            holder.itemView.setOnClickListener(v -> mItemClickListener.onItemClick(holder.getAdapterPosition()));
        }
        if (mLongClickListener != null) {
            holder.itemView.setOnLongClickListener(v -> mLongClickListener.onLongClick(holder.getAdapterPosition()));
        }

        // 绑定怎么办？回传出去
        convert(holder, mData.get(position));
    }

    /**
     * 利用抽象方法回传出去，每个不一样的Adapter去设置
     * @param holder ViewHolder
     * @param item 当前的数据
     */
    public abstract void convert(ViewHolder holder, T item);

    @Override
    public int getItemCount() {
        return mData.size();
    }

    /***************
     * 给条目设置点击和长按事件
     *********************/
    public OnItemClickListener mItemClickListener;
    public OnItemLongClickListener mLongClickListener;

    public void setOnItemClickListener(OnItemClickListener itemClickListener) {
        this.mItemClickListener = itemClickListener;
    }

    public void setOnLongClickListener(OnItemLongClickListener longClickListener) {
        this.mLongClickListener = longClickListener;
    }
}

创建可添加头部和尾部的RecyclerView

先创建WrapRecyclerAdapter适配器

public class WrapRecyclerAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    private final static String TAG = "WrapRecyclerAdapter";
    // 用来存放底部和头部View的集合  比Map要高效一些
    // 可以点击进入看一下官方的解释
    /**
     * SparseArrays map integers to Objects.  Unlike a normal array of Objects,
     * there can be gaps in the indices.  It is intended to be more memory efficient
     * than using a HashMap to map Integers to Objects, both because it avoids
     * auto-boxing keys and its data structure doesn't rely on an extra entry object
     * for each mapping.
     */
    private final SparseArray<View> mHeaderViews;
    private final SparseArray<View> mFooterViews;

    /**
     * 基本的头部类型开始位置  用于viewType
     */
    private static  int BASE_ITEM_TYPE_HEADER = 10000000;
    /**
     * 基本的底部类型开始位置  用于viewType
     */
    private static  int BASE_ITEM_TYPE_FOOTER = 20000000;

    /**
     * 列表的Adapter
     */
    private final RecyclerView.Adapter mAdapter;

    public WrapRecyclerAdapter(RecyclerView.Adapter adapter) {
        this.mAdapter = adapter;
        mHeaderViews = new SparseArray<>();
        mFooterViews = new SparseArray<>();
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // viewType 可能就是 SparseArray 的key
        if (isHeaderViewType(viewType)) {
            View headerView = mHeaderViews.get(viewType);
            return createHeaderFooterViewHolder(headerView);
        }
        if (isFooterViewType(viewType)) {
            View footerView = mFooterViews.get(viewType);
            return createHeaderFooterViewHolder(footerView);
        }
        return mAdapter.onCreateViewHolder(parent, viewType);
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
        if (isHeaderPosition(position) || isFooterPosition(position)) {
            return;
        }
        // 计算一下位置
        final int adapterPosition = position - mHeaderViews.size();
        mAdapter.onBindViewHolder(holder, adapterPosition);

        // 设置点击和长按事件
        if (mItemClickListener != null) {
            holder.itemView.setOnClickListener(v -> mItemClickListener.onItemClick(adapterPosition));
        }
        if (mLongClickListener != null) {
            holder.itemView.setOnLongClickListener(v -> mLongClickListener.onLongClick(adapterPosition));
        }
    }

    @Override
    public int getItemCount() {
        // 条数三者相加 = 底部条数 + 头部条数 + Adapter的条数
        return mAdapter.getItemCount() + mHeaderViews.size() + mFooterViews.size();
    }

    /**
     * 是不是底部类型
     */
    private boolean isFooterViewType(int viewType) {
        int position = mFooterViews.indexOfKey(viewType);
        return position >= 0;
    }

    /**
     * 是不是底部位置
     */
    private boolean isFooterPosition(int position) {
        return position >= (mHeaderViews.size() + mAdapter.getItemCount());
    }

    /**
     * 是不是头部位置
     */
    private boolean isHeaderPosition(int position) {
        return position < mHeaderViews.size();
    }

    /**
     * 创建头部或者底部的ViewHolder
     */
    private RecyclerView.ViewHolder createHeaderFooterViewHolder(View view) {
        return new RecyclerView.ViewHolder(view) {
        };
    }

    /**
     * 是不是头部类型
     */
    private boolean isHeaderViewType(int viewType) {
        int position = mHeaderViews.indexOfKey(viewType);
        return position >= 0;
    }

    @Override
    public int getItemViewType(int position) {
        if (isHeaderViewType(position)) {
            // 直接返回position位置的key
            return mHeaderViews.keyAt(position);
        }
        if (isFooterPosition(position)) {
            // 直接返回position位置的key
            position = position - mHeaderViews.size() - mAdapter.getItemCount();
            return mFooterViews.keyAt(position);
        }
        // 返回列表Adapter的getItemViewType
        position = position - mHeaderViews.size();
        return mAdapter.getItemViewType(position);
    }
    /**
     * 获取列表的Adapter
     */
    private RecyclerView.Adapter getAdapter() {
        return mAdapter;
    }

    /**
     * 添加头部
     */
    public void addHeaderView(View view) {
        int position = mHeaderViews.indexOfValue(view);
        if (position < 0) {
            mHeaderViews.put(BASE_ITEM_TYPE_HEADER++, view);
        }
        notifyDataSetChanged();
    }

    /**
     * 添加底部
     */
    public void addFooterView(View view) {
        int position = mFooterViews.indexOfValue(view);
        if (position < 0) {
            mFooterViews.put(BASE_ITEM_TYPE_FOOTER++, view);
        }
        notifyDataSetChanged();
    }

    /**
     * 移除头部
     */
    public void removeHeaderView(View view) {
        int index = mHeaderViews.indexOfValue(view);
        if (index < 0) {
            return;
        }
        mHeaderViews.removeAt(index);
        notifyDataSetChanged();
    }

    /**
     * 移除底部
     */
    public void removeFooterView(View view) {
        int index = mFooterViews.indexOfValue(view);
        if (index < 0) {
            return;
        }
        mFooterViews.removeAt(index);
        notifyDataSetChanged();
    }

    /**
     * 解决GridLayoutManager添加头部和底部不占用一行的问题
     *
     * @param recycler
     * @version 1.0
     */
    public void adjustSpanSize(RecyclerView recycler) {
        if (recycler.getLayoutManager() instanceof GridLayoutManager) {
            final GridLayoutManager layoutManager = (GridLayoutManager) recycler.getLayoutManager();
            layoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
                @Override
                public int getSpanSize(int position) {
                    boolean isHeaderOrFooter =
                            isHeaderPosition(position) || isFooterPosition(position);
                    return isHeaderOrFooter ? layoutManager.getSpanCount() : 1;
                }
            });
        }
    }

    /***************
     * 给条目设置点击和长按事件
     *********************/
    public OnItemClickListener mItemClickListener;
    public OnItemLongClickListener mLongClickListener;

    public void setOnItemClickListener(OnItemClickListener itemClickListener) {
        this.mItemClickListener = itemClickListener;
    }

    public void setOnLongClickListener(OnItemLongClickListener longClickListener) {
        this.mLongClickListener = longClickListener;
    }

}

创建可以添加头部和底部的RecyclerView

public class WrapRecyclerView extends RecyclerView {
    /**
     * 包裹了一层的头部底部Adapter
     */
    private WrapRecyclerAdapter mWrapRecyclerAdapter;
    /**
     * 这个是列表数据的Adapter
     */
    private RecyclerView.Adapter mAdapter;

    /**
     * 增加一些通用功能
     * 空列表数据应该显示的空View
     * 正在加载数据页面，也就是正在获取后台接口页面
     */
    private View mEmptyView, mLoadingView;

    public WrapRecyclerView(Context context) {
        super(context);
    }

    public WrapRecyclerView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public WrapRecyclerView(Context context, @Nullable AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public void setAdapter(Adapter adapter) {
        // 为了防止多次设置Adapter
        if (mAdapter != null) {
            mAdapter.unregisterAdapterDataObserver(mDataObserver);
            mAdapter = null;
        }

        this.mAdapter = adapter;

        if (adapter instanceof WrapRecyclerAdapter) {
            mWrapRecyclerAdapter = (WrapRecyclerAdapter) adapter;
        } else {
            mWrapRecyclerAdapter = new WrapRecyclerAdapter(adapter);
        }

        super.setAdapter(mWrapRecyclerAdapter);

        // 注册一个观察者
        mAdapter.registerAdapterDataObserver(mDataObserver);

        // 解决GridLayout添加头部和底部也要占据一行
        mWrapRecyclerAdapter.adjustSpanSize(this);

        // 加载数据页面
        if (mLoadingView != null && mLoadingView.getVisibility() == View.VISIBLE) {
            mLoadingView.setVisibility(View.GONE);
        }

        if (mItemClickListener != null) {
            mWrapRecyclerAdapter.setOnItemClickListener(mItemClickListener);
        }

        if (mLongClickListener != null) {
            mWrapRecyclerAdapter.setOnLongClickListener(mLongClickListener);
        }
    }

    /**
     * 添加头部
     */
    public void addHeaderView(View view) {
        // 如果没有Adapter那么就不添加，也可以选择抛异常提示
        // 让他必须先设置Adapter然后才能添加，这里是仿照ListView的处理方式
        if (mWrapRecyclerAdapter != null) {
            mWrapRecyclerAdapter.addHeaderView(view);
        }
    }

    /**
     * 添加底部
     */
    public void addFooterView(View view) {
        if (mWrapRecyclerAdapter != null) {
            mWrapRecyclerAdapter.addFooterView(view);
        }
    }

    /**
     * 移除头部
     */
    public void removeHeaderView(View view) {
        if (mWrapRecyclerAdapter != null) {
            mWrapRecyclerAdapter.removeHeaderView(view);
        }
    }

    /**
     * 移除底部
     */
    public void removeFooterView(View view) {
        if (mWrapRecyclerAdapter != null) {
            mWrapRecyclerAdapter.removeFooterView(view);
        }
    }

    private final AdapterDataObserver mDataObserver = new AdapterDataObserver() {
        @Override
        public void onChanged() {
            if (mAdapter == null) {
                return;
            }
            // 观察者  列表Adapter更新 包裹的也需要更新不然列表的notifyDataSetChanged没效果
            if (mWrapRecyclerAdapter != mAdapter) {
                mWrapRecyclerAdapter.notifyDataSetChanged();
            }

            dataChanged();
        }

        @Override
        public void onItemRangeRemoved(int positionStart, int itemCount) {
            if (mAdapter == null) {
                return;
            }
            // 观察者  列表Adapter更新 包裹的也需要更新不然列表的notifyDataSetChanged没效果
            if (mWrapRecyclerAdapter != mAdapter) {
                mWrapRecyclerAdapter.notifyItemRemoved(positionStart);
            }
            dataChanged();
        }

        @Override
        public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
            if (mAdapter == null) {
                return;
            }
            // 观察者  列表Adapter更新 包裹的也需要更新不然列表的notifyItemMoved没效果
            if (mWrapRecyclerAdapter != mAdapter) {
                mWrapRecyclerAdapter.notifyItemMoved(fromPosition, toPosition);
            }
            dataChanged();
        }

        @Override
        public void onItemRangeChanged(int positionStart, int itemCount) {
            if (mAdapter == null) {
                return;
            }
            // 观察者  列表Adapter更新 包裹的也需要更新不然列表的notifyItemChanged没效果
            if (mWrapRecyclerAdapter != mAdapter) {
                mWrapRecyclerAdapter.notifyItemChanged(positionStart);
            }
            dataChanged();
        }

        @Override
        public void onItemRangeChanged(int positionStart, int itemCount, Object payload) {
            if (mAdapter == null) {
                return;
            }
            // 观察者  列表Adapter更新 包裹的也需要更新不然列表的notifyItemChanged没效果
            if (mWrapRecyclerAdapter != mAdapter) {
                mWrapRecyclerAdapter.notifyItemChanged(positionStart, payload);
            }
            dataChanged();
        }

        @Override
        public void onItemRangeInserted(int positionStart, int itemCount) {
            if (mAdapter == null) {
                return;
            }
            // 观察者  列表Adapter更新 包裹的也需要更新不然列表的notifyItemInserted没效果
            if (mWrapRecyclerAdapter != mAdapter) {
                mWrapRecyclerAdapter.notifyItemInserted(positionStart);
            }
            dataChanged();
        }
    };

    /**
     * 添加一个空列表数据页面
     */
    public void addEmptyView(View emptyView) {
        this.mEmptyView = emptyView;
    }

    /**
     * 添加一个正在加载数据的页面
     */
    public void addLoadingView(View loadingView) {
        this.mLoadingView = loadingView;
        mLoadingView.setVisibility(View.VISIBLE);
    }

    /**
     * Adapter数据改变的方法
     */
    private void dataChanged() {
        if (mAdapter.getItemCount() == 0) {
            // 没有数据
            if (mEmptyView != null) {
                mEmptyView.setVisibility(VISIBLE);
            } else {
                mEmptyView.setVisibility(GONE);
            }
        }
    }

    /***************
     * 给条目设置点击和长按事件
     *********************/
    public OnItemClickListener mItemClickListener;
    public OnItemLongClickListener mLongClickListener;

    public void setOnItemClickListener(OnItemClickListener itemClickListener) {
        this.mItemClickListener = itemClickListener;

        if (mWrapRecyclerAdapter != null) {
            mWrapRecyclerAdapter.setOnItemClickListener(mItemClickListener);
        }
    }

    public void setOnItemLongClickListener(OnItemLongClickListener longClickListener) {
        this.mLongClickListener = longClickListener;

        if (mWrapRecyclerAdapter != null) {
            mWrapRecyclerAdapter.setOnLongClickListener(mLongClickListener);
        }
    }
}

使用方法

public class ImageListAdapter extends BaseRecyclerAdapter<UserBean> {
}