viewpager实现自动循环轮播图

android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<RelativeLayout
 android:layout_width="match_parent"
 android:layout_height="wrap_content">
 <androidx.viewpager.widget.ViewPager
  android:id="@+id/vp_adv"
  android:layout_width="match_parent"
  android:layout_height="160dp"/>
<LinearLayout
  android:id="@+id/View_indicator"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:layout_below="@id/vp_adv"
  android:layout_marginTop="-25dp"
  android:orientation="horizontal"
  android:gravity="right">
 </LinearLayout>
 </RelativeLayout>
</LinearLayout>

public class MainActivity extends AppCompatActivity {
 private ImageView indicator;//表示圆点指示器
 private ImageView [] indicators;//保存圆点指示器的数组
 private boolean iscontinue = true;
 private ViewPager viewPager;
 private ViewGroup viewGroup;
 private ArrayList<Fragment> fragments;
 List<Integer> imgs = null;
 private AtomicInteger index = new AtomicInteger();
 private Handler viewHandler= new Handler(){
 @Override
 public void handleMessage(@NonNull Message msg) {
  super.handleMessage(msg);
  viewPager.setCurrentItem(msg.what);
 }
 };

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 initView();
 }
 public void initView(){
 viewPager=findViewById(R.id.vp_adv);
 viewGroup=findViewById(R.id.View_indicator);
 //四张广告图片加载到集合中进行保存
 List<View> listPics = new ArrayList<>();
 ImageView img1 = new ImageView(this);
 img1.setBackgroundResource(R.mipmap.food1);
 listPics.add(img1);
 ImageView img2 = new ImageView(this);
 img1.setBackgroundResource(R.mipmap.shop2);
 listPics.add(img2);
 ImageView img3 = new ImageView(this);
 img1.setBackgroundResource(R.mipmap.shop3);
 listPics.add(img3);
 ImageView img4 = new ImageView(this);
 img1.setBackgroundResource(R.mipmap.shop4);
 listPics.add(img4);
 initFragments();
 //动态设置四个圆点属性
 indicators = new ImageView[listPics.size()];
 for(int i=0;i<indicators.length;i++){
  indicator = new ImageView(this);
  indicator.setLayoutParams(new LinearLayout.LayoutParams(40,40));
  indicator.setPadding(5,5,5,5);
  indicators[i] = indicator;
  if(i == 0){
  indicators[i].setBackgroundResource(R.drawable.ic_launcher_background);
  }else{
  indicators[i].setBackgroundResource(R.drawable.ic_launcher_foreground);
  }
  viewGroup.addView(indicators[i]);
 }
 //设置ViewPager适配器
 viewPager.setAdapter(new pagerAdapter(getSupportFragmentManager()));

 //设置viewPager监听器
 viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
  @Override
  public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

  }

  @Override
  public void onPageSelected(int position) {
  index.getAndSet(position);
  for(int i = 0;i <indicators.length; i ++){
   if(i ==position){
   indicators[i].setBackgroundResource(R.drawable.a1);
   }else{
   indicators[i].setBackgroundResource(R.drawable.a2);
   }
  }

  }

  @Override
  public void onPageScrollStateChanged(int state) {

  }
 });
 viewPager.setOnTouchListener(new View.OnTouchListener() {
  @Override
  public boolean onTouch(View view, MotionEvent motionEvent) {
  switch (motionEvent.getAction()){
   case MotionEvent.ACTION_DOWN:
   iscontinue = false;
   break;
   case MotionEvent.ACTION_UP:
   iscontinue = true;
   break;
  }
  return false;
  }
 });
 //使用多线程切换UI
 new Thread(new Runnable() {
  @Override
  public void run() {
  while (true){
   if(iscontinue){
   viewHandler.sendEmptyMessage(index.get());
   whatOption();
   }
  }

  }
 }).start();
 }
 private void whatOption(){
 index.incrementAndGet();//将当前位置+1；
 if(index.get()>indicators.length-1){
  index.getAndAdd(-4);
 }
 try {
  Thread.sleep(2000);
 } catch (InterruptedException e) {
  e.printStackTrace();
 }
 }
 private void initFragments() {
 imgs = new ArrayList<Integer>();
 imgs.add(R.mipmap.timg1);
 imgs.add(R.mipmap.timg2);
 imgs.add(R.mipmap.timg3);
 imgs.add(R.mipmap.timg4);

 }
 class pagerAdapter extends FragmentPagerAdapter{

 public pagerAdapter(FragmentManager fm) {
  super(fm);
 }

 @Override
 public Fragment getItem(int arg0) {
  //得到要显示的对象并初始化图片
  MyFragment fm = new MyFragment();
  fm.setUrl(imgs.get(arg0));

  return fm;
 }

 @Override
 public int getCount() {
  return imgs.size();
 }

 }
}

class MyPagerAdapter extends PagerAdapter{
 private List<View> viewList;
 public MyPagerAdapter(List<View>viewList){
 this.viewList = viewList;
 }

 @Override
 public int getCount() {
 return viewList.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(viewList.get(position));
 return viewList.get(position);
 }

 @Override
 public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
 container.removeView(viewList.get(position));
 }
}