安卓学习笔记-----为RecyclerView添加Header

为RecyclerView添加header

通过控制Adapter的itemType来设置，根据不同的itemType去加载不同的布局。
重写了getItemViewType方法，并根据位置来返回不同的type，然后在onCreateViewHolder方法中来判断itemType，如果是header，则返回设置的headerView，否则正常加载item布局
Adapter代码

public class HeaderAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    public static final int TYPE_HEADER = 0;
    public static final int TYPE_NORMAL = 1;
    private ArrayList<String> mDatas = new ArrayList<>();
    private View mHeaderView;
    private OnItemClickListener mListener;

    public void setonItemClickListener(OnItemClickListener li) {
        mListener = li;
    }

    public void setHeaderView(View headerView) {
        mHeaderView = headerView;
        notifyItemInserted(0);
    }

    public View getHeaderView() {
        return mHeaderView;
    }

    public void addDatas(ArrayList<String> datas) {
        mDatas.addAll(datas);
        notifyDataSetChanged();
    }

    @Override
    public int getItemViewType(int position) {
        if (mHeaderView == null) {
            return TYPE_NORMAL;
        }
        if (position == 0) {
            return TYPE_HEADER;
        }
        return TYPE_NORMAL;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (mHeaderView != null && viewType == TYPE_HEADER) {
            return new Holder(mHeaderView);
        }
        View layout = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
        return new Holder(layout);
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (getItemViewType(position) == TYPE_HEADER) {
            return;
        }

        final int pos = getRealPosition(holder);
        final String data = mDatas.get(pos);
        if (holder instanceof Holder) {
            ((Holder) holder).text.setText(data);
            if (mListener == null) {
                return;
            }
            holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mListener.onItemClick(pos, data);
                }
            });
        }

    }

    public int getRealPosition(RecyclerView.ViewHolder holder) {
        int position = holder.getPosition();
        return mHeaderView == null ? position : position - 1;
    }

    @Override
    public int getItemCount() {
        return mHeaderView == null ? mDatas.size() : mDatas.size() + 1;
    }


    class Holder extends RecyclerView.ViewHolder {
        TextView text;

        public Holder(View itemView) {
            super(itemView);
            if (itemView == mHeaderView) {
                return;
            }
            text = (TextView) itemView.findViewById(R.id.num);
        }
    }

    interface OnItemClickListener {
        void onItemClick(int position, String data);
    }
}

下面是MainActivity

public class HeaderAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    public static final int TYPE_HEADER = 0;
    public static final int TYPE_NORMAL = 1;
    private ArrayList<String> mDatas = new ArrayList<>();
    private View mHeaderView;
    private OnItemClickListener mListener;

    public void setonItemClickListener(OnItemClickListener li) {
        mListener = li;
    }

    public void setHeaderView(View headerView) {
        mHeaderView = headerView;
        notifyItemInserted(0);
    }

    public View getHeaderView() {
        return mHeaderView;
    }

    public void addDatas(ArrayList<String> datas) {
        mDatas.addAll(datas);
        notifyDataSetChanged();
    }

    @Override
    public int getItemViewType(int position) {
        if (mHeaderView == null) {
            return TYPE_NORMAL;
        }
        if (position == 0) {
            return TYPE_HEADER;
        }
        return TYPE_NORMAL;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (mHeaderView != null && viewType == TYPE_HEADER) {
            return new Holder(mHeaderView);
        }
        View layout = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
        return new Holder(layout);
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (getItemViewType(position) == TYPE_HEADER) {
            return;
        }

        final int pos = getRealPosition(holder);
        final String data = mDatas.get(pos);
        if (holder instanceof Holder) {
            ((Holder) holder).text.setText(data);
            if (mListener == null) {
                return;
            }
            holder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mListener.onItemClick(pos, data);
                }
            });
        }

    }

    public int getRealPosition(RecyclerView.ViewHolder holder) {
        int position = holder.getPosition();
        return mHeaderView == null ? position : position - 1;
    }

    @Override
    public int getItemCount() {
        return mHeaderView == null ? mDatas.size() : mDatas.size() + 1;
    }


    class Holder extends RecyclerView.ViewHolder {
        TextView text;

        public Holder(View itemView) {
            super(itemView);
            if (itemView == mHeaderView) {
                return;
            }
            text = (TextView) itemView.findViewById(R.id.num);
        }
    }

    interface OnItemClickListener {
        void onItemClick(int position, String data);
    }
}

刚开始看着教程写的云里雾里的，写完之后看了一下讲解，然后又看了几遍代码才搞明白Adapter里是怎样设置的。