Android 使用ViewPager实现手动左右切换页面和底部点点跟随切换效果

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:background="#DFDFDF"
    tools:context=".MainActivity">
    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_margin="5dp"
        android:background="@color/white" />
  <!--在java代码中添加点点图片-->
    <LinearLayout
        android:id="@+id/viewGroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="8dp"
        android:orientation="horizontal" />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="第一个页面"
        android:textSize="20sp" />
</LinearLayout>

public class MyPagerAdapter extends PagerAdapter {
    private ArrayList<View> viewArrayList = new ArrayList<>();
    public MyPagerAdapter(ArrayList<View> viewArrayList) {
        this.viewArrayList = viewArrayList;
    }
    @Override
    public int getCount() {
        return viewArrayList.size();
    }
    @Override
    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
        return view == object;
    }
    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {
        container.addView(viewArrayList.get(position),0);
        return viewArrayList.get(position);
    }
    @Override
    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
        container.removeView(viewArrayList.get(position));
    }
}

public class MainActivity extends AppCompatActivity {
    private MyPagerAdapter myPagerAdapter;
    private ViewPager viewPager;
    private LinearLayout viewGroup;
    private ArrayList<View> viewArrayList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        viewPager = findViewById(R.id.viewPager);
        viewGroup = findViewById(R.id.viewGroup);
        @SuppressLint("InflateParams") View carousel_first = LayoutInflater.from(this).inflate(R.layout.carousel_first, null);
        @SuppressLint("InflateParams") View carousel_second = LayoutInflater.from(this).inflate(R.layout.carousel_second, null);
        @SuppressLint("InflateParams") View carousel_third = LayoutInflater.from(this).inflate(R.layout.carousel_third, null);
        viewArrayList.add(carousel_first);
        viewArrayList.add(carousel_second);
        viewArrayList.add(carousel_third);
        //将点点的图添加到视图ViewGroup中
        for (int i = 0; i < viewArrayList.size(); i++) {
            ImageView imageView = new ImageView(this);
            //设置图片的宽高 为10像素
            imageView.setLayoutParams(new ViewGroup.LayoutParams(10, 10));
            if (i == 0) {
                //第一个为默认选中状态
                imageView.setImageResource(R.drawable.icon_page_select);
            } else {
                imageView.setImageResource(R.drawable.icon_page_normal);
            }
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
            params.leftMargin = 5;
            params.rightMargin = 5;
            viewGroup.addView(imageView, params);
        }
        myPagerAdapter = new MyPagerAdapter(viewArrayList);
        //设置缓存页数
        viewPager.setOffscreenPageLimit(viewArrayList.size() - 1);
        viewPager.setAdapter(myPagerAdapter);
        //添加页面更改监听器
        viewPager.addOnPageChangeListener(onPageChangeListener);
    }
    private ViewPager.OnPageChangeListener onPageChangeListener = new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
        }
        @Override
        public void onPageSelected(int position) {
            //当新页面选中时调用此方法，position 为新选中页面的位置索引
            //在所选页面的时候,点点图片也要发生变化
            setImageBackground(position);
        }
        @Override
        public void onPageScrollStateChanged(int state) {
        }
    };
    /**
     * 改变点点点的切换效果
     *
     * @param selectItem 当前选中的页面索引
     */
    private void setImageBackground(int selectItem) {
        for (int i = 0; i < viewArrayList.size(); i++) {
            ImageView imageView = (ImageView) viewGroup.getChildAt(i);
            imageView.setBackground(null);
            if (i == selectItem) {
                imageView.setImageResource(R.drawable.icon_page_select);
            } else {
                imageView.setImageResource(R.drawable.icon_page_normal);
            }
        }
    }
}