前言

ViewPager2是androidx.viewpager2.widget包下面的，用来代替androidx.viewpager.widget.ViewPager，而androidx是用来代替原来的support库的
为了紧跟时代发展，很有必要学习ViewPager2，ViewPager2是由RecyclerView加上LinearLayoutManager并继承自ViewGroup而来

参考文章
https://www.jianshu.com/p/bd70970600aa
https://blog.csdn.net/xiangshiweiyu_hd/article/details/104005810
https://blog.csdn.net/diyangxia/article/details/94458274

一、ViewPager2的基本使用

1.1、导入依赖

implementation 'androidx.viewpager2:viewpager2:1.0.0'
implementation 'androidx.recyclerview:recyclerview:1.1.0' // ViewPager 2 需要使用 RecycleView 的 adapter

1.2、activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

   <androidx.viewpager2.widget.ViewPager2
       android:layout_width="match_parent"
       android:layout_height="match_parent"
      android:id="@+id/viewPager"
      android:background="@color/colorAccent">

   </androidx.viewpager2.widget.ViewPager2>

</LinearLayout>

1.3、ViewPagerAdapter.java

ViewPager2的适配器
注意：这里继承的是RecyclerView.Adapter<ViewPagerAdapter.ViewPagerViewHolder>
因为ViewPager2的底层实现是RecyclerView

package com.example.viewpagerandfragment;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

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

public class ViewPagerAdapter extends RecyclerView.Adapter<ViewPagerAdapter.ViewPagerViewHolder> {
    private List<String> titles = new ArrayList<>();
    private List<Integer> colors = new ArrayList<>();

    //模拟数据
    public ViewPagerAdapter(){
        titles.add("zzuli");
        titles.add("移动软件");
        titles.add("516");
        titles.add("study");
        titles.add("I");
        titles.add("like");
        titles.add("you");
        titles.add("my");
        titles.add("best");
        titles.add("wish");

        colors.add(R.color.white);
        colors.add(R.color.black);
        colors.add(R.color.red);
        colors.add(R.color.colorAccent);
        colors.add(R.color.colorPrimary);
        colors.add(R.color.white);
        colors.add(R.color.black);
        colors.add(R.color.red);
        colors.add(R.color.colorPrimary);
        colors.add(R.color.white);

    }

    /**
     * 绑定布局以及属性
     * @param parent
     * @param viewType
     * @return
     */
    @NonNull
    @Override
    public ViewPagerViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new ViewPagerViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_pager, parent, false));
    }

    /**
     * 设置数据
     * @param holder
     * @param position
     */
    @Override
    public void onBindViewHolder(@NonNull ViewPagerViewHolder holder, int position) {
        holder.mTv.setText(titles.get(position));
        holder.mContainer.setBackgroundResource(colors.get(position));
    }


    /**
     * 页面的数量
     * @return
     */
    @Override
    public int getItemCount() {
        return 10;
    }

    /**
     * 绑定布局以及属性
     */
    class ViewPagerViewHolder extends RecyclerView.ViewHolder{

        TextView mTv;
        RelativeLayout mContainer;
        public ViewPagerViewHolder(@NonNull View itemView) {
            super(itemView);
            mContainer = itemView.findViewById(R.id.container);
            mTv = itemView.findViewById(R.id.tvTitle);
        }
    }
}

1.4、单页面布局

item_pager.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/container">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

        android:id="@+id/tvTitle"
        android:layout_centerInParent="true"
        android:textColor="#ff4532"
        android:textSize="32dp"
        android:text="hello"></TextView>
</RelativeLayout>

1.5、MainActivity.java

package com.example.viewpagerandfragment;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.RecyclerView;
import androidx.viewpager2.widget.ViewPager2;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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

        ViewPager2 viewPager = findViewById(R.id.viewPager);
        
        //设置适配器
        ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter();
        viewPager.setAdapter(viewPagerAdapter);
    }
}