Android RecyclerView实现子元素的Group分组，LinearLayoutManager垂直方向详解手机开发

我使用LinearLayoutManager实现一个常见的分组RecyclerView，所谓分组，就是把RecyclerView的元素分类归整到一个组中，常见的联系人、通讯录，往往会以姓名、姓氏作为分组的组。重点是使用RecyclerView的Item viewType。
代码：

package app.zhangphil.app; 
 
import android.graphics.Color; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.support.v7.widget.LinearLayoutManager; 
import android.support.v7.widget.RecyclerView; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.TextView; 
 
import java.util.ArrayList; 
 
public class MainActivity extends AppCompatActivity { 
 
    private final int TYPE_GROUP = 0xa01; 
    private final int TYPE_CHILD = 0xa02; 
    private String[] groupNames = {"A", "B", "C", "D", "E", "F", "G"}; 
    private ArrayList<Item> mItems; 
 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.activity_main); 
 
        mItems = new ArrayList<>(); 
        for (int i = 0; i < groupNames.length; i++) { 
            Group group = new Group(); 
            group.position = i; 
            group.title = groupNames[i]; 
            mItems.add(group); 
 
            int count = (int) (Math.random() * 10) % 4 + 1; 
            for (int j = 0; j < count; j++) { 
                Child child = new Child(); 
                child.position = j; 
                child.groupPos = i; 
                child.groupName = group.title; 
                mItems.add(child); 
            } 
        } 
 
        RecyclerView mRecyclerView = findViewById(R.id.recycler_view); 
 
        //GridLayoutManager layoutManage = new GridLayoutManager(this, 4); 
        LinearLayoutManager layoutManage = new LinearLayoutManager(this); 
        layoutManage.setOrientation(LinearLayoutManager.VERTICAL); 
        
        mRecyclerView.setLayoutManager(layoutManage); 
 
        RecyclerViewAdapter mAdapter = new RecyclerViewAdapter(); 
        mRecyclerView.setAdapter(mAdapter); 
    } 
 
    public class RecyclerViewAdapter extends RecyclerView.Adapter<ItemVH> { 
 
        @Override 
        public ItemVH onCreateViewHolder(ViewGroup parent, int viewType) { 
            View view; 
            ItemVH itemVH = null; 
            switch (viewType) { 
                case TYPE_GROUP: 
                    view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_1, parent, false); 
                    itemVH = new GroupVH(view); 
                    break; 
 
                case TYPE_CHILD: 
                    view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_2, parent, false); 
                    itemVH = new ChildVH(view); 
                    break; 
            } 
 
            return itemVH; 
        } 
 
        @Override 
        public void onBindViewHolder(ItemVH holder, int position) { 
            Item item = mItems.get(position); 
            switch (getItemViewType(position)) { 
                case TYPE_GROUP: 
                    Group g = (Group) item; 
                    GroupVH groupVH = (GroupVH) holder; 
                    groupVH.text1.setText(g.title); 
                    break; 
 
                case TYPE_CHILD: 
                    Child c = (Child) item; 
                    ChildVH childVH = (ChildVH) holder; 
                    childVH.text1.setText(c.groupName); 
                    childVH.text2.setText(c.position + ""); 
                    break; 
            } 
        } 
 
        @Override 
        public int getItemCount() { 
            return mItems.size(); 
        } 
 
        @Override 
        public int getItemViewType(int position) { 
            return mItems.get(position).getType(); 
        } 
    } 
 
    private class Group extends Item { 
        public String title; 
 
        @Override 
        public int getType() { 
            return TYPE_GROUP; 
        } 
    } 
 
    private class Child extends Item { 
        public int groupPos; 
        public String groupName; 
 
        @Override 
        public int getType() { 
            return TYPE_CHILD; 
        } 
    } 
 
    private abstract class Item { 
        public int position; 
 
        public abstract int getType(); 
    } 
 
    private class GroupVH extends ItemVH { 
        public TextView text1; 
 
        public GroupVH(View itemView) { 
            super(itemView); 
            text1 = itemView.findViewById(android.R.id.text1); 
            text1.setBackgroundColor(Color.RED); 
        } 
 
        @Override 
        public int getType() { 
            return TYPE_GROUP; 
        } 
    } 
 
    private class ChildVH extends ItemVH { 
        public TextView text1; 
        public TextView text2; 
 
        public ChildVH(View itemView) { 
            super(itemView); 
            text1 = itemView.findViewById(android.R.id.text1); 
            text2 = itemView.findViewById(android.R.id.text2); 
            text1.setTextColor(Color.LTGRAY); 
            text2.setTextColor(Color.BLUE); 
        } 
 
        @Override 
        public int getType() { 
            return TYPE_CHILD; 
        } 
    } 
 
    private abstract class ItemVH extends RecyclerView.ViewHolder { 
        public ItemVH(View itemView) { 
            super(itemView); 
        } 
 
        public abstract int getType(); 
    } 
}

运行结果如图：

附录：

1，《Android RecyclerView的StaggeredGridLayoutManager和CardView》链接：https://blog.csdn.net/zhangphil/article/details/47604581