RecyclerView添加Header和Footer的基本原理

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• GitHub

介绍

• 采用的基本原理就是Header和Footer作为RecyclerView的一个Item，只是显示的方式特别一点，ListView实际也是这么做的所以添加了Header之后，数据的位置会错乱。

• 由于使用不同的LayoutManager时显示效果也不一样， 所以针对不同的LayoutManager需要做不同的操作。

• 分析一下，LinearLayoutManager比较简单，只需要将Header和Footer作为一项就可以了，GridLayoutManager和StaggeredGridLayoutManager在这个基础上还需要将Header和Footer所在的Item充满他所在的这一行。

变量和方法

//Header和Footer,以及对应的Typeprivate View mHeaderView;private View mFooterView;private int TYPE_HEADER = -1;private int TYPE_FOOTER = -2;//一些辅助的方法public int getHeaderCount() {        return isHasHeader() ? 1 : 0;}private boolean isHasHeader() {        return mHeaderView != null;}private boolean isHasFooter() {        return mFooterView != null;}

根据是否有Header和Footer获取数据Size

//根据是否有Header和Footer返回不同的Size@Overridepublic int getItemCount() {        int pos = datas.size();        if (isHasHeader())            pos++;        if (isHasFooter())            pos++;        return pos;}

根据是否有Header和Footer获取Type

//获取item的type，基本逻辑是如果有header又是位于第一个的则返回HeaderType,如果pos超出了data的size，又是最后一个，则返回FooterType@Overridepublic int getItemViewType(int position) {        //如果没有header没有footer直接返回        if (!isHasHeader() && !isHasFooter())            return datas.get(position).getRvType();        //有header且位置0        if (isHasHeader() && position == 0)            return TYPE_HEADER;        //pos超出        if (isHasFooter() && position == getItemCount() - 1)            return TYPE_FOOTER;        //如果有header,下标减一个        if (isHasHeader())            return datas.get(position - 1).getRvType();        else            //没有header 按照原来的            return datas.get(position).getRvType();}

根据是否有Header和Footer创建Holder

//根据返回的不同的type使用HeaderView和FooterView初始化Holder,至此已经可以对LinearLayoutManager添加Header和Footer@Overridepublic RvViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        RvViewHolder holder;        if (isHasFooter() && viewType == TYPE_FOOTER) {            holder = new RvFooterHolder(mFooterView);        } else if (isHasHeader() && viewType == TYPE_HEADER) {            holder = new RvHeaderHolder(mHeaderView);        } else {            holder = new RvViewHolder(getInflateView(Res4Type.get(viewType).getResId(),         return holder;}

LinearLayoutManager

• 由于LinearLayoutManager是连续排列的，所以只需要创建不同的holder就可以实现header+footer

GridLayoutManager

• 首先如何知道是否是GridLayoutManager,重写onAttachedToRecyclerView方法获取Manager,调用gridLayoutManager.setSpanSizeLookup（）方法，设置他跨越的宽度。

@Overridepublic void onAttachedToRecyclerView(RecyclerView recyclerView) {        super.onAttachedToRecyclerView(recyclerView);        Log.e("chendong","onAttachedToRecyclerView");        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) {            final GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;            gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {                @Override                public int getSpanSize(int position) {                    return getItemViewType(position) == TYPE_HEADER || getItemViewType(position) == TYPE_FOOTER                            ? gridLayoutManager.getSpanCount() : 1;                }            });            return;        }         //判断是不是StaggeredGridLayoutManager        if(layoutManager instanceof StaggeredGridLayoutManager){            isStaggeredGridLayoutManager = true;        }}

StaggeredGridLayoutManager

• 主要使用StaggeredGridLayoutManager.LayoutParams的 layoutParams.setFullSpan(true);方法设置

@Overridepublic RvViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        RvViewHolder holder;        if (isHasFooter() && viewType == TYPE_FOOTER) {            holder = new RvFooterHolder(mFooterView);        } else if (isHasHeader() && viewType == TYPE_HEADER) {            holder = new RvHeaderHolder(mHeaderView);        } else {            holder = new RvViewHolder(getInflateView(Res4Type.get(viewType).getResId(), parent));            if (clickListener != null) {                holder.setOnItemClickListener(clickListener);            }            if (longClickListenter != null) {                holder.setOnItemLongClickListener(longClickListenter);            }        }         //关键代码        if (isStaggeredGridLayoutManager && (holder instanceof RvHeaderHolder || holder instanceof RvFooterHolder)) {            Log.e("chendong","瀑布流设置满行");            StaggeredGridLayoutManager.LayoutParams layoutParams = new StaggeredGridLayoutManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);            layoutParams.setFullSpan(true);            holder.getParentView().setLayoutParams(layoutParams);        }        bindListener4View(holder, viewType);        return holder;}

QuickAdapter

• 最后贴一下整个QuickAdapter的源代码，涉及相关具体的类可以去这里查看

package com.march.quickrvlibs;import android.content.Context;import android.support.v7.widget.GridLayoutManager;import android.support.v7.widget.RecyclerView;import android.support.v7.widget.StaggeredGridLayoutManager;import android.util.Log;import android.util.SparseArray;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import com.march.quickrvlibs.inter.OnRecyclerItemClickListener;import com.march.quickrvlibs.inter.OnRecyclerItemLongClickListener;import com.march.quickrvlibs.inter.RvQuickInterface;import java.util.Collections;import java.util.List;/** * Created by 陈栋 on 15/12/28. * 功能: */public abstract class RvQuickAdapter<D extends RvQuickInterface> extends RecyclerView.Adapter<RvViewHolder> {    protected List<D> datas;    protected LayoutInflater mLayoutInflater;    protected Context context;    protected SparseArray<RvAdapterConfig> Res4Type;    private OnRecyclerItemClickListener<RvViewHolder> clickListener;    private OnRecyclerItemLongClickListener<RvViewHolder> longClickListenter;    private View mHeaderView;    private View mFooterView;    private int TYPE_HEADER = -1;    private int TYPE_FOOTER = -2;    private int adapterId;//使用此标志来判断当前adapter的类型    private boolean isStaggeredGridLayoutManager   = false;    public int getAdapterId() {        return adapterId;    }    /**     * 设置adapterId标示     * @param adapterId adapter标示     */    public void setAdapterId(int adapterId) {        this.adapterId = adapterId;    }    /**     * 使用标记判断,是否是该adaper     * @param adapter adapter     * @return boolean     */    public boolean isThisAdapter(RvQuickAdapter adapter) {        if (adapter == null) {            return false;        } else if (adapter.getAdapterId() == adapterId) {            return true;        }        return false;    }    /**     * 多类型适配,需要调用addType()方法配置参数     *     * @param context context     * @param datas   数据源     */    public RvQuickAdapter(Context context, List<D> datas) {        this.datas = datas;        this.mLayoutInflater = LayoutInflater.from(context);        this.context = context;    }    public RvQuickAdapter(Context context, D[] ds) {        Collections.addAll(datas, ds);        this.mLayoutInflater = LayoutInflater.from(context);        this.context = context;    }    /**     * 单类型适配     *     * @param context context     * @param datas   数据源     * @param res     layout资源     */    public RvQuickAdapter(Context context, List<D> datas, int res) {        this.datas = datas;        this.mLayoutInflater = LayoutInflater.from(context);        this.context = context;        this.Res4Type = new SparseArray<>();        Res4Type.put(0, new RvAdapterConfig(0, res));    }    public RvQuickAdapter(Context context, D[] ds, int res) {        Collections.addAll(datas, ds);        this.mLayoutInflater = LayoutInflater.from(context);        this.context = context;        this.Res4Type = new SparseArray<>();        Res4Type.put(0, new RvAdapterConfig(0, res));    }    public void setClickListener(OnRecyclerItemClickListener<RvViewHolder> listener) {        if (listener != null) {            this.clickListener = listener;        }    }    public void setLongClickListener(OnRecyclerItemLongClickListener<RvViewHolder> longClickListenter) {        if (longClickListenter != null) {            this.longClickListenter = longClickListenter;        }    }    public void addHeader(View mHeaderView) {        this.mHeaderView = mHeaderView;    }    public void addFooter(View mFooterView) {        this.mFooterView = mFooterView;    }    public void addHeader(int mHeaderViewRes) {        this.mHeaderView = getInflateView(mHeaderViewRes, null);    }    public void addFooter(int mFooterViewRes) {        this.mFooterView = getInflateView(mFooterViewRes, null);    }    public View getInflateView(int resId, ViewGroup parent) {        return mLayoutInflater.inflate(resId, parent, false);    }    @Override    public RvViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        RvViewHolder holder;        if (isHasFooter() && viewType == TYPE_FOOTER) {            holder = new RvFooterHolder(mFooterView);        } else if (isHasHeader() && viewType == TYPE_HEADER) {            holder = new RvHeaderHolder(mHeaderView);        } else {            holder = new RvViewHolder(getInflateView(Res4Type.get(viewType).getResId(), parent));            if (clickListener != null) {                holder.setOnItemClickListener(clickListener);            }            if (longClickListenter != null) {                holder.setOnItemLongClickListener(longClickListenter);            }        }        if (isStaggeredGridLayoutManager && (holder instanceof RvHeaderHolder || holder instanceof RvFooterHolder)) {            Log.e("chendong","瀑布流设置满行");            StaggeredGridLayoutManager.LayoutParams layoutParams = new StaggeredGridLayoutManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);            layoutParams.setFullSpan(true);            holder.getParentView().setLayoutParams(layoutParams);        }        bindListener4View(holder, viewType);        return holder;    }    @Override    public void onBindViewHolder(RvViewHolder holder, int position) {        if (isHasFooter() && position == getItemCount() - 1) {            bindLisAndData4Footer((RvFooterHolder) holder);        } else if (isHasHeader() && position == 0) {            bindLisAndData4Header((RvHeaderHolder) holder);        } else {            int pos = judgePos(position);            bindData4View(holder, datas.get(pos), pos, datas.get(pos).getRvType());        }    }    @Override    public int getItemViewType(int position) {        //如果没有header没有footer直接返回        if (!isHasHeader() && !isHasFooter())            return datas.get(position).getRvType();        //有header且位置0        if (isHasHeader() && position == 0)            return TYPE_HEADER;        //pos超出        if (isHasFooter() && position == getItemCount() - 1)            return TYPE_FOOTER;        //如果有header,下标减一个        if (isHasHeader())            return datas.get(position - 1).getRvType();        else            //没有header 按照原来的            return datas.get(position).getRvType();    }    private int judgePos(int pos) {        if (isHasHeader()) {            return pos - 1;        } else {            return pos;        }    }    @Override    public void onAttachedToRecyclerView(RecyclerView recyclerView) {        super.onAttachedToRecyclerView(recyclerView);        Log.e("chendong","onAttachedToRecyclerView");        RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();        if (layoutManager instanceof GridLayoutManager) {            final GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;            gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {                @Override                public int getSpanSize(int position) {                    return getItemViewType(position) == TYPE_HEADER || getItemViewType(position) == TYPE_FOOTER                            ? gridLayoutManager.getSpanCount() : 1;                }            });            return;        }        if(layoutManager instanceof StaggeredGridLayoutManager){            isStaggeredGridLayoutManager = true;        }    }    /**     * 绑定数据     *     * @param holder ViewHolder数据持有者     * @param data   数据集     * @param pos    数据集中的位置     * @param type   type     */    public abstract void bindData4View(RvViewHolder holder, D data, int pos, int type);    /**     * 绑定监听器     *     * @param holder ViewHolder数据持有者     * @param type   type     */    public void bindListener4View(RvViewHolder holder, int type) {    }    /**     * 绑定header的数据 和  监听     *     * @param holder header holder     */    public void bindLisAndData4Header(RvHeaderHolder holder) {    }    /**     * 绑定footer的数据和监听     *     * @param holder footer holder     */    public void bindLisAndData4Footer(RvFooterHolder holder) {    }    @Override    public int getItemCount() {        int pos = datas.size();        if (isHasHeader())            pos++;        if (isHasFooter())            pos++;        return pos;    }    public int getHeaderCount() {        return isHasHeader() ? 1 : 0;    }    public int getDataPos(int pos) {        return pos - getHeaderCount();    }    private boolean isHasHeader() {        return mHeaderView != null;    }    private boolean isHasFooter() {        return mFooterView != null;    }    /**     * @param type  数据的类型(如果有n种类型,那么type的值需要是0 ~ n-1)     * @param resId 该类型对应的资源文件的id     * @return QuickTypeAdapter     */    public RvQuickAdapter<D> addType(int type, int resId) {        if (this.Res4Type == null)            this.Res4Type = new SparseArray<>();        this.Res4Type.put(type, new RvAdapterConfig(type, resId));        return this;    }}