RecyclerView Adapter使用心得

作者：庄超人
链接：https://www.jianshu.com/p/42254630bdce

因为发展趋势变成了使用RecyclerView来替代ListVIew，但网上大部分博客写的内容相对简单，很多用法没讲清楚，自己在使用过程中走了不少弯路，特此记录一下自己的心得。首先是继承父类

extends RecyclerView.Adapter<RecyclerView.ViewHolder>

需要实现以下几个函数

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    return null;
}

@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {}

@Override
public int getItemCount() {
    return 0;
}

onCreateViewHolder()负责为Item创建视图，onBindViewHolder()负责将数据绑定到Item的视图上。那么接下来就需要有ViewHolder了。

public class MenuItemViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    private TextView newsType;
    public MenuItemViewHolder(View v) {
        super(v);
        newsType =  (TextView)v.findViewById(R.id.tv_item);
    }

    @Override 
    public void onClick(View v) {
        if (mOnItemClickListener != null) {
            mOnItemClickListener.onItemClick(v, this.getPosition());
        }
    }
}

以上就是基本的用法，通过这些内容就可以使用一个建议的RecyclerView。
但如果这个RecyclerView里需要设置多种Item的view视图，这就需要设置好几个变量并用到这个函数

private static final int TYPE_TOPIC = 0;
private static final int TYPE_TITLE = 1;

Override
public int getItemViewType(int position) {}

通过getItemViewType()为每个item设置好它的类型后在即可在onCreateViewHolder()根据Type创建相应的视图。
如果需要像ListView一样使用headerView，则需要预先自定义一个HeaderView，示例如下

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

并在ViewHolder对其进行设置。

public MainTopicViewHolder (View itemView) {
    super(itemView);
    if (itemView == mHeaderView) return;
    tv_topic = (TextView) itemView.findViewById(R.id.tv_topic);
}

在设置监听时，需要在Adapter里定义好接口和set的函数

private OnItemClickListener mOnItemClickListener;
public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
    this.mOnItemClickListener = onItemClickListener;
}
public interface OnItemClickListener {
    void onItemClick(View view, int position);
}

及在onBindViewHolder()绑定的时候将监听器也绑定上

if (mOnItemClickListener != null) {
    ((MainTopicViewHolder) holder).itemView.setOnClickListener(new View.OnClickListener() {
        Override
        public void onClick(View v) {
            int pos = holder.getLayoutPosition();
            mOnItemClickListener.onItemClick(holder.itemView, pos);
        }
    });
}

以后在此基础上另有心得时再补充，附上一个完整示例

public class MainNewsAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    private static final int TYPE_HEADER = 0;
    private static final int TYPE_TOPIC = 1;
    private static final int TYPE_TITLE = 2;
    private Context mContext;
    private OnItemClickListener mOnItemClickListener;
    private List list;
    private ImageLoader imageLoader;
    private DisplayImageOptions displayImageOptions;
    private View mHeaderView;
    public MainNewsAdapter(Context context) {
        mContext = context;
        list = new ArrayList<>();
        imageLoader = ImageLoader.getInstance();
        displayImageOptions = new DisplayImageOptions.Builder().cacheInMemory(true).cacheOnDisk(true).build();
    }
    public void addList(List items) {
        this.list.addAll(items);notifyDataSetChanged();
    }
    public void setHeaderView(View headerView) {
        mHeaderView = headerView;
        notifyItemInserted(0);
    }
    public View getHeaderView() {
        return mHeaderView;
    }
    public StoriesEntity getItem(int position) {
        return list.get(position-1);
    }
    @Override
    public int getItemViewType(int position) {
        if (position == 0) {
            return TYPE_HEADER;
        } else {
            StoriesEntity entity = list.get(position-1);
            if (entity.getType() == Constant.TOPIC) {
                return TYPE_TOPIC;
            } else {
                return TYPE_TITLE;
            }
        }
    }
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == TYPE_TOPIC) {
            View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.main_news_topic, parent, false);
            MainTopicViewHolder mainTopicViewHolder = new MainTopicViewHolder(v);
            return mainTopicViewHolder;
        } else if (viewType == TYPE_TITLE) {
            View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.main_news_item, parent, false);
            MainNewsViewHolder mainNewsViewHolder = new MainNewsViewHolder(v);
            return mainNewsViewHolder;
        } else {
            MainTopicViewHolder mainTopicViewHolder = new MainTopicViewHolder(mHeaderView);
            return mainTopicViewHolder;
        }
    }
    @Override
    public void onBindViewHolder(final RecyclerView.ViewHolder holder, int position) {
        if (position == 0) {
            return;
        }
        if (holder instanceof MainNewsViewHolder) {
            StoriesEntity entity = list.get(position — 1);
            ((MainNewsViewHolder) holder).tv_title.setText(entity.getTitle());
            imageLoader.displayImage(entity.getImages().get(0),((MainNewsViewHolder) holder).iv_title, displayImageOptions);
            if (mOnItemClickListener != null) {
                ((MainNewsViewHolder) holder).itemView.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        int pos = holder.getLayoutPosition();
                        mOnItemClickListener.onItemClick(holder.itemView, pos);
                    }
                 });
            }
        } else {
            StoriesEntity entity = list.get(position-1);          
            ((MainTopicViewHolder) holder).tv_topic.setVisibility(View.VISIBLE);((MainTopicViewHolder) holder).tv_topic.setText(entity.getTitle());
            if (mOnItemClickListener != null) {
                ((MainTopicViewHolder) holder).itemView.setOnClickListener(new View.OnClickListener()     
                    @Override
                    public void onClick(View v) {
                        int pos = holder.getLayoutPosition();
                        mOnItemClickListener.onItemClick(holder.itemView, pos);
                    }
                });
            }
        }
    }
    @Override
    public int getItemCount() {
        return mHeaderView == null ? list.size() : list.size() + 1;
    }
    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        this.mOnItemClickListener = onItemClickListener;
    }
    public interface OnItemClickListener {
        void onItemClick(View view, int position);
    }
    public class MainTopicViewHolder extends RecyclerView.ViewHolder {
        TextView tv_topic;
        public MainTopicViewHolder(View itemView) {
            super(itemView);
            if (itemView == mHeaderView) return;
            tv_topic = (TextView) itemView.findViewById(R.id.tv_topic);
        }
    }
    public class MainNewsViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        TextView tv_title;
        ImageView iv_title;
        public MainNewsViewHolder(View itemView) {          
            super(itemView);
            tv_title = (TextView) itemView.findViewById(R.id.tv_title);
            iv_title = (ImageView) itemView.findViewById(R.id.iv_title);}
            @Override
            public void onClick(View v) {
                if (mOnItemClickListener != null) {
                    mOnItemClickListener.onItemClick(v, this.getPosition());
                }
            }
    }
}