在RecyclerView中加载不同布局

当RecyclerView有下拉刷新时，有时候设计图上，体现出来的列表有头部布局，这可以通过Adapter实现加载多套布局就可以，这里以加载两种布局为例说明。

先看看Adapter的代码

import android.annotation.SuppressLint;
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

import com.alvin.R;

import java.util.ArrayList;
import java.util.List;

public class MainListAdapter extends RecyclerView.Adapter{
    private List list;
    private ArrayList jdList;
    private Context context;

    public MainListAdapter(List list,ArrayList jdList, Context context) {
        this.list = list;
        this.jdList = jdList;
        this.context = context;
    }
    @Override
    public int getItemViewType(int position) {
        return list.get(position).getShowType();
    }
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if(viewType==1){
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_header_main_list,parent,false);
            return new HeaderHolder(view);
        }else{
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_list_main,parent,false);
            return new ViewHolderItem(view);
        }
    }

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

        if(holder instanceof HeaderHolder){
            final HeaderHolder headerHolder = (HeaderHolder) holder;
            //TODO 实现相关逻辑
        }else if(holder instanceof ViewHolderItem){

        }
    }

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

    private class HeaderHolder extends RecyclerView.ViewHolder{
        
        HeaderHolder(View itemView) {
            super(itemView);
        }
    }

    private class ViewHolderItem extends RecyclerView.ViewHolder{

        ViewHolderItem(View itemView) {
            super(itemView);
        }
    }

    
}

getItemViewType()这个返回的是列表当前布局类型，在Adapter加载布局时，对齐进行判断，也就是onBindViewHolder()方法中进行相应的判断逻辑实现。

如果layoutmanager是GridLayoutManager，header布局需要独占spanCount的，也就是如果是两列，header宽度就是两列

layoutManager = GridLayoutManager(this, 2)
recyclerView.layoutManager = layoutManager
//.........
//比如：
layoutManager?.let {
            it.spanSizeLookup = object : GridLayoutManager.SpanSizeLookup(){
                override fun getSpanSize(position: Int): Int {
                    if(position==0){
                        return it.spanCount
                    }else{
                        return 1
                    }
                }
            }
        }