Android Viewpager无限循环轮播图 Android Viewpager实现无限循环轮播图

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Android Viewpager无限循环轮播图 Android Viewpager实现无限循环轮播图

xia236326   2021-03-30 我要评论

在网上找了很多viewpager实现图片轮播的，但是大多数通过以下方式在PagerAdapter的getCount()返回一个无限大的数，来实现 伪无限

@Override
 public int getCount() {
  return Integer.MAX_VALUE;//返回一个无限大的值，可以 无限循环
 }

虽然通过这种方式是能达到效果，但是从严格意义上来说并不是真正的无限。

假如有五张轮播图 item的编号为（0,1,2,3,4） 要想实现 无限循环  我们在这五张的头部和尾部各加一张即（5+2）张,item编号为（0,1,2,3,4,5,6）其中编号为0,6的两张不做展示只是为了做循环轮播的铺垫，使得播放更加平滑。

1、当我们从编号为5 右滑的时候到了编号6 这时候就将当前页面设置为1

2、当我们从编号为1左滑的时候到了编号0  这时候就将当前页面设置为5

这么做之后就可以实现无限轮播  怎么保证从编号6跳转编号1的时候不出现页面停顿 突然跳到下一页的现象呢？

public Object instantiateItem (ViewGroup container, int position)

在指定的位置创建页面；适配器负责添加view到这个容器中，然而它只保证在finishUpdate(ViewGroup)返回时才完成。

public void destroyItem (ViewGroup container, int position, Object object)

删除指定位置的页面；适配器负责从view容器中删除view，然而它只保证在finishUpdate(ViewGroup)返回时才完成。

所以说 重点就在于finishUpdate(ViewGroup)这个方法 其实无论是创建view添加到容器中  还是 销毁view 都是在此方法结束之后执行的

换句话说  就是 我在这个方法里让页面完成从 编号5跳转到编号1 或者从编号1跳转到编号5，此方法完成时 视图还未完成创建或者 销毁 这样也就不会出现 页面停顿 突然跳到下一页的现象。

@Override
 public void finishUpdate(ViewGroup container) {
  super.finishUpdate(container);
 
  int position = viewPager.getCurrentItem();
  
  if (position == 0) {
   position = simpleDraweeViewList.size() - 2;
   viewPager.setCurrentItem(position,false);
  } else if (position == simpleDraweeViewList.size() - 1) {
   position = 1;
   viewPager.setCurrentItem(position,false);
  }
 }

话不多说，上代码：

布局文件：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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">
 
 <FrameLayout
  android:id="@+id/frameLayout"
  android:layout_width="0dp"
  android:layout_height="200dp"
  app:layout_constraintEnd_toEndOf="parent"
  app:layout_constraintHorizontal_bias="0.0"
  app:layout_constraintStart_toStartOf="parent"
  app:layout_constraintTop_toTopOf="parent">
 
  <android.support.v4.view.ViewPager
   android:id="@+id/viewPager"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:layout_editor_absoluteX="8dp"
   tools:layout_editor_absoluteY="0dp" />
 
  <LinearLayout
   android:layout_width="match_parent"
   android:layout_height="35dip"
   android:layout_gravity="bottom"
   android:background="#33000000"
   android:gravity="center_vertical"
   android:orientation="horizontal"
   android:weightSum="10">
 
   <TextView
    android:id="@+id/tv_pager_title"
    android:layout_width="0dp"
    android:layout_height="35dip"
    android:layout_weight="8"
    android:gravity="center_vertical"
    android:paddingLeft="8dip"
    android:text="加载图片轮播失败"
    android:textColor="@android:color/white" />
 
   <LinearLayout
    android:id="@+id/lineLayout_dot"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_marginRight="5dp"
    android:layout_weight="2"
    android:gravity="center|right"
    android:orientation="horizontal"
    android:paddingLeft="3dp"
    android:paddingRight="3dp" />
 
  </LinearLayout>
 
 </FrameLayout>
 
</android.support.constraint.ConstraintLayout>

最主要的PagerAdapter：

import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
 
import com.facebook.drawee.view.SimpleDraweeView;
 
import java.util.List;
 
public class ImagesPagerAdapter extends PagerAdapter {
 private List<SimpleDraweeView> simpleDraweeViewList;
 private ViewPager viewPager;
 private Context context;
 
 private SimpleDraweeView simpleDraweeView;
 
 public ImagesPagerAdapter(List<SimpleDraweeView> simpleDraweeViewList, ViewPager viewPager, Context context) {
  this.simpleDraweeViewList = simpleDraweeViewList;
  this.viewPager = viewPager;
  this.context = context;
 }
 
 @Override
 public int getCount() {
 return simpleDraweeViewList.size();
 }
 
 //删除指定位置的页面；适配器负责从view容器中删除view，然而它只保证在finishUpdate(ViewGroup)返回时才完成。
 @Override
 public void destroyItem(ViewGroup container, int position, Object object) {
  // 把ImageView从ViewPager中移除掉
  viewPager.removeView(simpleDraweeViewList.get(position));
  //super.destroyItem(container, position, object);
 }
 
 //是否获取缓存
 @Override
 public boolean isViewFromObject(View view, Object object) {
  return view == object;
 }
 
 
 //实例化Item
 //在指定的位置创建页面；适配器负责添加view到这个容器中，然而它只保证在finishUpdate(ViewGroup)返回时才完成。
 @Override
 public Object instantiateItem(ViewGroup container, int position) {
  simpleDraweeView = simpleDraweeViewList.get(position);
  viewPager.addView(simpleDraweeView);
  return simpleDraweeView;
 }
 
 @Override
 public int getItemPosition(Object object) {
  return POSITION_NONE;
 }
 
 //无论是创建view添加到容器中 还是 销毁view 都是在此方法结束之后执行的
 @Override
 public void finishUpdate(ViewGroup container) {
  super.finishUpdate(container);
 
  int position = viewPager.getCurrentItem();
  
  if (position == 0) {
   position = simpleDraweeViewList.size() - 2;
   viewPager.setCurrentItem(position,false);
  } else if (position == simpleDraweeViewList.size() - 1) {
   position = 1;
   viewPager.setCurrentItem(position,false);
  }
 }
 
 
 
/* private int mChildCount = 0;
 @Override
 public void notifyDataSetChanged() {
  mChildCount = getCount();
  super.notifyDataSetChanged();
 }
 @Override
 public int getItemPosition(Object object) {
  if (mChildCount > 0) {
   mChildCount--;
   Log.e("image","getItemPosition");
   return POSITION_NONE;
  }
  return super.getItemPosition(object);
 }*/
}

import android.app.Activity;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.support.v4.content.ContextCompat;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
 
import com.facebook.drawee.view.SimpleDraweeView;
 
import java.util.ArrayList;
import java.util.List;
 
 
 
public class ImageCarousel {
 private Context context;
 private ViewPager viewPager;
 private TextView tvTitle;
 private LinearLayout dotsRoot;
 private int time;
 
 
 private List<View> dots;//小点
 private int previousPosition = 1;//前一个被选中的position
 private List<SimpleDraweeView> simpleDraweeViewList;
 private String[] titles;//标题数组
 
 private ImagesPagerAdapter adapter;
 
 private AutoPlayThread autoPlayThread;
 private volatile boolean isExit = true;
 
 private static final int FIRST_PAGE = 1;
 
 
 public ImageCarousel(Context context, ViewPager viewPager, TextView tvTitle,
       List<View> dots, int time) {
  this.context = context;
  this.viewPager = viewPager;
  this.tvTitle = tvTitle;
  this.dots = dots;
  this.time = time;
  Log.e("image", "构造方法");
 }
 
 
 
 /**
  * 传入数据
  *
  * @param simpleDraweeViewList SimpleDraweeView集合
  * @param titles    标题数组
  * @return this 本身
  */
 public ImageCarousel init(List<SimpleDraweeView> simpleDraweeViewList, String[] titles) {
  this.simpleDraweeViewList = simpleDraweeViewList;
  this.titles = titles;
  Log.e("image", "init");
  autoPlayThread = new AutoPlayThread();
 
  return this;
 }
 
 /**
  * 重新加载，有待考验...
  *
  * @param simpleDraweeViewList SimpleDraweeView集合
  * @param titles    标题数组
  */
 public void reload(List<SimpleDraweeView> simpleDraweeViewList, String[] titles) {
  init(simpleDraweeViewList, titles);
  previousPosition = 0;
  start();
 }
 
 /**
  * 设置设配器，并实现轮播功能
  */
 public void start() {
  if (adapter != null) {
   adapter = null;
  }
  adapter = new ImagesPagerAdapter(this.simpleDraweeViewList, viewPager, context);
  viewPager.setAdapter(adapter);
  viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
   @Override
   public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
 
   }
 
   //当被选择
   @Override
   public void onPageSelected(int position) {
 
    int currentPosition = 1;
    if (position == simpleDraweeViewList.size() - 1) {
     // 设置当前值为1
     currentPosition = FIRST_PAGE;
    } else if (position == 0) {
     // 如果索引值为0了,就设置索引值为倒数第二个
     currentPosition = simpleDraweeViewList.size() - 2;
    } else {
     currentPosition = position;
    }
 
    // 把当前选中的点给切换了, 还有描述信息也切换
    tvTitle.setText(titles[currentPosition]);//图片下面设置显示文本
    //设置轮播点 可设置成传入的图
 
    Log.d("dots", "previousPosition=" + previousPosition + " currentPosition=" + currentPosition);
    dots.get(previousPosition-1).setBackgroundResource(R.drawable.ic_dot_focused);
    dots.get(currentPosition-1).setBackgroundResource(R.drawable.ic_dot_normal);
    // 把当前的索引赋值给前一个索引变量, 方便下一次再切换.
    previousPosition = currentPosition;
   }
 
   @Override
   public void onPageScrollStateChanged(int state) {
 // SCROLL_STATE_IDLE ：空闲状态 
 // SCROLL_STATE_DRAGGING ：滑动状态 
 // SCROLL_STATE_SETTLING ：滑动后滑翔的状态
    if (state == ViewPager.SCROLL_STATE_DRAGGING) {
 
    } else if(state == ViewPager.SCROLL_STATE_IDLE){
  
 }
   }
  });
 
  setFirstLocation();
  //autoPlayThread.start();
 
 }
 
 /**
  * 设置刚打开app时显示的图片和文字
  */
 private void setFirstLocation() {
  tvTitle.setText(titles[0]);
  dots.get(0).setBackgroundResource(R.drawable.ic_dot_normal);
  viewPager.setCurrentItem(1);
 }
 
 /**
  * 设置是否轮播
  *
  * @param b
  */
 private void setAutoPlay(boolean b) {
  /*if (b && suspendRequested) {
   autoPlayThread.requestResume();
  } else if (!b){
   autoPlayThread.requestSuspend();
  }*/
 }
 
 
 public void stopAutoPlay() {
  if (autoPlayThread != null) {
   Log.e("thrad", "暂停");
   isExit = true;
   autoPlayThread.interrupt();
   autoPlayThread = null;
  }
 }
 
 /**
  * 请求继续
  */
 public void startAutoPlay() {
  Log.e("thrad", "开始");
  isExit = false;
  autoPlayThread = null;
  autoPlayThread = new AutoPlayThread();
  autoPlayThread.start();
 }
 
 /**
  * 自动播放线程，添加暂停和继续方法
  */
 class AutoPlayThread extends Thread {
 
  @Override
  public synchronized void run() {
   while (!isExit) {
    try {
     Thread.sleep(time);
    } catch (InterruptedException e) {
     Log.e("thrad", "强制请求退出线程");
     break;
    }
    ((Activity) context).runOnUiThread(new Runnable() {
     @Override
     public void run() {
      viewPager.setCurrentItem(viewPager.getCurrentItem() + 1);
     }
    });
 
    if (this.interrupted()) {
     Log.e("thrad", "已经是停止状态了，我要退出了");
     break;
    }
   }
 
  }
 
 }
 
}

mainActivity.java:

import android.app.Activity;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.support.v4.content.ContextCompat;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.LinearLayout;
import android.widget.TextView;
 
import com.facebook.drawee.backends.pipeline.Fresco;
import com.facebook.drawee.backends.pipeline.PipelineDraweeController;
import com.facebook.drawee.drawable.ScalingUtils;
import com.facebook.drawee.generic.GenericDraweeHierarchy;
import com.facebook.drawee.generic.GenericDraweeHierarchyBuilder;
import com.facebook.drawee.view.SimpleDraweeView;
import com.facebook.imagepipeline.common.ResizeOptions;
import com.facebook.imagepipeline.request.ImageRequest;
import com.facebook.imagepipeline.request.ImageRequestBuilder;
 
import java.util.ArrayList;
import java.util.List;
 
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
 
 // 图片轮播控件
 private ViewPager mViewPager;
 private TextView mTvPagerTitle;
 private LinearLayout mLineLayoutDot;
 private ImageCarousel imageCarousel;
 private List<View> dots;//小点
 
 // 图片数据，包括图片标题、图片链接、数据、点击要打开的网站（点击打开的网页或一些提示指令）
 private List<ImageInfo> imageInfoList;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  initView();
  initEvent();
  imageStart();
 
 }
 
 @Override
 public void onClick(View v) {
 
 }
 
 /**
  * 初始化事件
  * 左右多添加一张图片
  */
 private void initEvent() {
  imageInfoList = new ArrayList<>();
 imageInfoList.add(new ImageInfo(1, "图片5，公告5啦啦啦啦", "", "/image/h%3D300/sign=73443062281f95cab9f594b6f9177fc5/72f082025aafa40fafb5fbc1a664034f78f019be.jpg", ""));
  imageInfoList.add(new ImageInfo(2, "图片1，公告1啦啦啦啦", "", "/image/pic/item/6159252dd42a2834a75bb01156b5c9ea15cebf2f.jpg", ""));
  imageInfoList.add(new ImageInfo(3, "图片2，公告2啦啦啦啦", "", "/image/h%3D300/sign=cfce96dfa251f3dedcb2bf64a4eff0ec/4610b912c8fcc3ce912597269f45d688d43f2039.jpg", ""));
  imageInfoList.add(new ImageInfo(4, "图片3，公告3啦啦啦啦", "", "/image/pic/item/6a600c338744ebf85ed0ab2bd4f9d72a6059a705.jpg", ""));
  imageInfoList.add(new ImageInfo(5, "图片4，公告4啦啦啦啦", "", "/image/h%3D300/sign=8ad802f3801001e9513c120f880e7b06/a71ea8d3fd1f4134be1e4e64281f95cad1c85efa.jpg", ""));
  imageInfoList.add(new ImageInfo(6, "图片5，公告5啦啦啦啦", "", "/image/h%3D300/sign=73443062281f95cab9f594b6f9177fc5/72f082025aafa40fafb5fbc1a664034f78f019be.jpg", ""));
 imageInfoList.add(new ImageInfo(7, "图片1，公告1啦啦啦啦", "", "/image/pic/item/6159252dd42a2834a75bb01156b5c9ea15cebf2f.jpg", ""));
 
 }
 
 /**
  * 初始化控件
  */
 private void initView() {
 
  mViewPager = findViewById(R.id.viewPager);
  mTvPagerTitle = findViewById(R.id.tv_pager_title);
  mLineLayoutDot = findViewById(R.id.lineLayout_dot);
 
 }
 
 private void imageStart() {
  //设置图片轮播
  int[] imgaeIds = new int[]{R.id.pager_image1, R.id.pager_image2, R.id.pager_image3, R.id.pager_image4,
    R.id.pager_image5, R.id.pager_image6, R.id.pager_image7, R.id.pager_image8};
  String[] titles = new String[imageInfoList.size()];
  List<SimpleDraweeView> simpleDraweeViewList = new ArrayList<>();
 
  for (int i = 0; i < imageInfoList.size(); i++) {
   titles[i] = imageInfoList.get(i).getTitle();
   SimpleDraweeView simpleDraweeView = new SimpleDraweeView(this);
   simpleDraweeView.setAspectRatio(1.78f);
   // 设置一张默认的图片
   GenericDraweeHierarchy hierarchy = new GenericDraweeHierarchyBuilder(this.getResources())
     .setPlaceholderImage(ContextCompat.getDrawable(this, R.drawable.defult), ScalingUtils.ScaleType.CENTER_CROP).build();
   simpleDraweeView.setHierarchy(hierarchy);
   simpleDraweeView.setLayoutParams(new AbsListView.LayoutParams(AbsListView.LayoutParams.MATCH_PARENT, AbsListView.LayoutParams.WRAP_CONTENT));
 
   //加载高分辨率图片;
   ImageRequest imageRequest = ImageRequestBuilder.newBuilderWithSource(Uri.parse(imageInfoList.get(i).getImage()))
     .setResizeOptions(new ResizeOptions(1280, 720))
     .build();
   PipelineDraweeController controller = (PipelineDraweeController) Fresco.newDraweeControllerBuilder()
     //.setLowResImageRequest(ImageRequest.fromUri(Uri.parse(listItemBean.test_pic_low))) //在加载高分辨率图片之前加载低分辨率图片
     .setImageRequest(imageRequest)
     .setOldController(simpleDraweeView.getController())
     .build();
   simpleDraweeView.setController(controller);
 
   simpleDraweeView.setId(imgaeIds[i]);//给view设置id
   simpleDraweeView.setTag(imageInfoList.get(i));
   simpleDraweeView.setOnClickListener(this);
   titles[i] = imageInfoList.get(i).getTitle();
   simpleDraweeViewList.add(simpleDraweeView);
 
  }
 
  dots = addDots(mLineLayoutDot, fromResToDrawable(this, R.drawable.ic_dot_focused), simpleDraweeViewList.size());
  imageCarousel = new ImageCarousel(this, mViewPager, mTvPagerTitle, dots, 5000);
  imageCarousel.init(simpleDraweeViewList, titles)
    .startAutoPlay();
  imageCarousel.start();
 
 }
 
 
 /**
  * 动态添加一个点
  *
  * @param linearLayout 添加到LinearLayout布局
  * @param backgount 设置
  * @return 小点的Id
  */
 private int addDot(final LinearLayout linearLayout, Drawable backgount) {
  final View dot = new View(this);
  LinearLayout.LayoutParams dotParams = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
    ViewGroup.LayoutParams.WRAP_CONTENT);
  dotParams.width = 16;
  dotParams.height = 16;
  dotParams.setMargins(4, 0, 4, 0);
  dot.setLayoutParams(dotParams);
  dot.setBackground(backgount);
  dot.setId(View.generateViewId());
  ((Activity) this).runOnUiThread(new Runnable() {
   @Override
   public void run() {
    linearLayout.addView(dot);
   }
  });
 
  return dot.getId();
 }
 
 
 /**
  * 资源图片转Drawable
  *
  * @param context 上下文
  * @param resId 资源ID
  * @return 返回Drawable图像
  */
 public static Drawable fromResToDrawable(Context context, int resId) {
  return ContextCompat.getDrawable(context, resId);
 }
 
 /**
  * 添加多个轮播小点到横向线性布局
  *
  * @param linearLayout 线性横向布局
  * @param backgount 小点资源图标
  * @param number  数量
  * @return 返回小点View集合
  */
 private List<View> addDots(final LinearLayout linearLayout, Drawable backgount, int number) {
  List<View> dots = new ArrayList<>();
  for (int i = 2; i < number; i++) { // 注意这里的 i 从 2 开始，只画出5个点
 
   int dotId = addDot(linearLayout, backgount);
   dots.add(findViewById(dotId));
 
  }
  return dots;
 }
 
 
}

ic_dot_focused.xml：

<vector android:height="5dp" android:viewportHeight="24.0"
 android:viewportWidth="24.0" android:width="5dp" xmlns:android="http://schemas.android.com/apk/res/android">
 <path android:fillColor="#c8ffffff" android:pathData="M12,12m-8,0a8,8 0,1 1,16 0a8,8 0,1 1,-16 0"/>
</vector>

ic_dot_normal.xml：

<vector android:height="5dp" android:viewportHeight="24.0"
 android:viewportWidth="24.0" android:width="5dp" xmlns:android="http://schemas.android.com/apk/res/android">
 <path android:fillColor="#c8fd8888" android:pathData="M12,12m-8,0a8,8 0,1 1,16 0a8,8 0,1 1,-16 0"/>
</vector>

当然这里主要是实现真正的无限轮播，其中对于 用户手动滑动图片时需要暂停轮播没有做相关处理。

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