实现加载头部和顶部布局的BaseAdapter

来源：互联网发布：一叶落而知深秋编辑：程序博客网时间：2024/06/06 15:46

首先判断当前加载哪种布局，重写getItemViewType方法

        if (position == 0) {            if (head_layout_id != 0) {                return TYPE_HEAD;            } else {                return TYPE_NULL;            }        }        if (position + 1 == getItemCount()) {            if (foot_layout_id != 0) {                return TYPE_FOOT;            } else {                return TYPE_NULL;            }        }        return TYPE_NORMAL;

在onCreateViewHolder中根据不同的viewType加载不同的布局，最好确保返回值不为空，不然可能会抛出异常

   @Override    public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        switch (viewType) {            case TYPE_HEAD:                headView = inflater.inflate(head_layout_id, parent, false);                return createHeadView(parent, viewType);            case TYPE_NORMAL:                itemView = inflater.inflate(normal_layout_id, parent, false);                return createItemView(parent, viewType);            case TYPE_FOOT:                footView = inflater.inflate(foot_layout_id, parent, false);                return createFootView(parent, viewType);            default:                return new BaseViewHolder(new View(context));        }    }

在onBindViewHolder中根据不同viewType绑定不同数据

    @Override    public void onBindViewHolder(BaseViewHolder holder, int position) {        if (position == 0) {            if (head_layout_id != 0) bindHeadView((HEAD) holder, 0);        } else if (position + 1 == getItemCount()) {            if (foot_layout_id != 0) bindFootView((FOOT) holder, position);        } else {            bindItemView((ITEM) holder, position);        }    }

子类中需重写的方法

    protected abstract ITEM createItemView(ViewGroup parent, int viewType);    protected abstract HEAD createHeadView(ViewGroup parent, int viewType);    protected abstract FOOT createFOOTView(ViewGroup parent, int viewType);    protected abstract void bindItemView(ITEM holder, int position);    protected abstract void bindHeadView(HEAD holder, int position);    protected abstract void bindFootView(FOOT holder, int position);

最后是完整的代码
BaseAdapter

public abstract class BaseAdapter<HEAD extends BaseViewHolder, ITEM extends BaseViewHolder, FOOT extends BaseViewHolder, DATA> extends RecyclerView.Adapter<BaseViewHolder> {    private final int TYPE_HEAD = 1;    private final int TYPE_NORMAL = 2;    private final int TYPE_FOOT = 3;    private final int TYPE_NULL = 4;    protected Context context;    protected LayoutInflater inflater;    protected int normal_layout_id;    protected int head_layout_id;    protected int foot_layout_id;    protected List<DATA> dataList;    protected View headView;    protected View itemView;    protected View footView;    protected OnLoadMoreListener onLoadMoreListener;    public BaseAdapter(Context context, int head_layout_id, int layout_id, int foot_layout_id, List<DATA> dataList) {        this.context = context;        this.foot_layout_id = foot_layout_id;        this.head_layout_id = head_layout_id;        this.normal_layout_id = layout_id;        this.dataList = dataList;        this.inflater = LayoutInflater.from(context);    }    @Override    public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        switch (viewType) {            case TYPE_HEAD:                headView = inflater.inflate(head_layout_id, parent, false);                return createHeadView(parent, viewType);            case TYPE_NORMAL:                itemView = inflater.inflate(normal_layout_id, parent, false);                return createItemView(parent, viewType);            case TYPE_FOOT:                footView = inflater.inflate(foot_layout_id, parent, false);                return createFootView(parent, viewType);            default:                return new BaseViewHolder(new View(context));        }    }    protected abstract ITEM createItemView(ViewGroup parent, int viewType);    protected abstract HEAD createHeadView(ViewGroup parent, int viewType);    protected abstract FOOT createFootView(ViewGroup parent, int viewType);    @Override    public void onBindViewHolder(BaseViewHolder holder, int position) {        if (position == 0) {            if (head_layout_id != 0) bindHeadView((HEAD) holder, 0);        } else if (position + 1 == getItemCount()) {            if (foot_layout_id != 0) bindFootView((FOOT) holder, position);        } else {            bindItemView((ITEM) holder, dataList.get(position - 1));        }    }    protected abstract void bindItemView(ITEM holder, DATA data);    protected abstract void bindHeadView(HEAD holder, int position);    protected abstract void bindFootView(FOOT holder, int position);    @Override    public int getItemViewType(int position) {        if (position == 0) {            if (head_layout_id != 0) {                return TYPE_HEAD;            } else {                return TYPE_NULL;            }        }        if (position + 1 == getItemCount()) {            if (foot_layout_id != 0) {                return TYPE_FOOT;            } else {                return TYPE_NULL;            }        }        return TYPE_NORMAL;    }    @Override    public int getItemCount() {        return dataList.size() + 2;    }    public void setOnLoadMoreListener(OnLoadMoreListener onLoadMoreListener) {        this.onLoadMoreListener = onLoadMoreListener;    }    public void clearData() {        if (dataList != null) dataList.clear();    }    public void addData(List<DATA> moreList) {        dataList.addAll(moreList);    }    //可手动添加一个加载更多失败的回调    public interface OnLoadMoreListener {        void loadMore(BaseViewHolder footHolder);    }}

BaseViewHolder

public class BaseViewHolder extends RecyclerView.ViewHolder {    public BaseViewHolder(View itemView) {        super(itemView);        ButterKnife.bind(this, itemView);    }}

DATA为需要绑定的数据类型

使用
依次传入头部，正常item，底部布局的ViewHolder还有实现数据绑定的数据类型

public class DemoAdapter extends BaseAdapter<HeadViewHolder,AdviceViewHolder,FootViewHolder,DesignAdvice>{    public DemoAdapter(Context context, int foot_layout_id, int head_layout_id, int layout_id, List<DesignAdvice> designAdvices) {        super(context, foot_layout_id, head_layout_id, layout_id, designAdvices);    }    @Override    protected AdviceViewHolder createItemView(ViewGroup parent, int viewType) {        return new AdviceViewHolder(itemView);    }    @Override    protected HeadViewHolder createHeadView(ViewGroup parent, int viewType) {        return new HeadViewHolder(headView);    }    @Override    protected FootViewHolder createFootView(ViewGroup parent, int viewType) {        return new FootViewHolder(footView);    }    @Override    protected void bindItemView(AdviceViewHolder holder, DesignAdvice designAdvice) {    //操作数据        holder.title.setText(designAdvice.getTitle());        holder.itemView.setTag(designAdvice);    }    @Override    protected void bindHeadView(HeadViewHolder holder, int position) {    }    @Override    protected void bindFootView(FootViewHolder holder, int position) {    }}

有时候我们并不需要头部和底部的布局，但直接继承这个BaseAdapter还是会有些多余的代码，所以我决定进一步封装一个只有正常item的adapter

DataAdapter

public abstract class DataAdapter<ITEM extends BaseViewHolder, DATA> extends BaseAdapter<BaseViewHolder, ITEM, BaseViewHolder, DATA> {    public DataAdapter(Context context, int layout_id, List<DATA> datas) {        super(context, 0, layout_id, 0, datas);    }    @Override    protected BaseViewHolder createHeadView(ViewGroup parent, int viewType) {        return null;    }    @Override    protected BaseViewHolder createFootView(ViewGroup parent, int viewType) {        return null;    }    @Override    protected void bindHeadView(BaseViewHolder holder, int position) {    }    @Override    protected void bindFootView(BaseViewHolder holder, int position) {    }}

代码也很简单，继承BaseAdapter，顶部和底部的布局id传入0即可，然后重写他们的createView和bindView方法。

使用

public class DemoAdapter extends DataAdapter<AdviceViewHolder, DesignAdvice> {    public DemoAdapter(Context context, int layout_id, List<DesignAdvice> designAdvices) {        super(context, layout_id, designAdvices);    }    @Override    protected AdviceViewHolder createItemView(ViewGroup parent, int viewType) {        return new AdviceViewHolder(itemView);    }    @Override    protected void bindItemView(AdviceViewHolder holder, DesignAdvice designAdvice) {        holder.title.setText(designAdvice.getTitle());        holder.itemView.setTag(designAdvice);    }}

直接传入布局的ViewHolder和需要处理的数据。我们只要把精力放在bindView中数据的显示即可了。需要写的代码基本只在bindView中了。也不用再去频繁的根据position获取List中的数据了，这些工作都已经封装好了。

类似的还可以封装有head和item的adapter以及有foot和item的adapter。要是三种都需要就使用BaseAdapter。

有底部布局和item的Adapter

public abstract class DataWFootAdapter<ITEM extends BaseViewHolder, FOOT extends BaseViewHolder, DATA> extends BaseAdapter<BaseViewHolder, ITEM, FOOT, DATA> {    public DataWFootAdapter(Context context,  int layout_id, int foot_layout_id, List<DATA> datas) {        super(context,0, layout_id, foot_layout_id, datas);    }    @Override    protected BaseViewHolder createHeadView(ViewGroup parent, int viewType) {        return null;    }    @Override    protected void bindHeadView(BaseViewHolder holder, int position) {    }}

有头部布局的Adapter

public abstract class DataWHeadAdapter<HEAD extends BaseViewHolder,ITEM extends BaseViewHolder, DATA> extends BaseAdapter<HEAD, ITEM, BaseViewHolder, DATA>{    public DataWHeadAdapter(Context context, int head_layout_id, int layout_id, int foot_layout_id, List<DATA> datas) {        super(context, head_layout_id, layout_id, foot_layout_id, datas);    }    @Override    protected BaseViewHolder createFootView(ViewGroup parent, int viewType) {        return null;    }    @Override    protected void bindFootView(BaseViewHolder holder, int position) {    }}

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