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linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);

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1引入依赖

implementation 'androidx.recyclerview:recyclerview:1.1.0'

2 MainActivity

package com.example.myapplication;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

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

public class MainActivity extends AppCompatActivity {

    private RecyclerView mRecyclerView;
    private List<String> mDatas;
    private HomeAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initData();
        mRecyclerView = (RecyclerView) findViewById(R.id.id_recyclerview);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
        mRecyclerView.setLayoutManager(linearLayoutManager);
        mRecyclerView.setAdapter(mAdapter = new HomeAdapter());

    }

    protected void initData()
    {
        mDatas = new ArrayList<String>();
        for (int i = 'A'; i < 'F'; i++)
        {
            mDatas.add("" + (char) i);
        }
    }

    class HomeAdapter extends RecyclerView.Adapter<HomeAdapter.MyViewHolder>
    {
        @NonNull
        @Override
        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
        {
            MyViewHolder holder = new MyViewHolder(LayoutInflater.from(
                    MainActivity.this).inflate(R.layout.item_home, parent,
                    false));
            return holder;
        }

        @NonNull


        @Override
        public void onBindViewHolder(MyViewHolder holder, int position)
        {
            holder.tv.setText(mDatas.get(position));
        }

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

        class MyViewHolder extends RecyclerView.ViewHolder
        {

            TextView tv;

            public MyViewHolder(View view)
            {
                super(view);
                tv = (TextView) view.findViewById(R.id.id_num);
            }
        }
    }
}

2 activity_main

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/id_recyclerview"
        android:divider="#ffff0000"
        android:dividerHeight="10dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

3 item_home

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:background="#44ff0000"
    android:layout_height="wrap_content" >

    <TextView
        android:id="@+id/id_num"
        android:background="@color/white"
        android:layout_width="200dp"
        android:layout_height="50dp"
        android:layout_marginRight="20dp"
        android:gravity="center"
        android:text="1" />
</FrameLayout>

横向RecyclerView实现_android