Android Viewpager实现无限循环轮播图

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：

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 simpleDraweeViewList;
  private ViewPager viewPager;
  private Context context;
 
  private SimpleDraweeView simpleDraweeView;
 
  public ImagesPagerAdapter(List 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 dots;//小点
  private int previousPosition = 1;//前一个被选中的position
  private List 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 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 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 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 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 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", "", "http://e.hiphotos.baidu.com/image/h%3D300/sign=73443062281f95cab9f594b6f9177fc5/72f082025aafa40fafb5fbc1a664034f78f019be.jpg", ""));
    imageInfoList.add(new ImageInfo(2, "图片1，公告1啦啦啦啦", "", "http://d.hiphotos.baidu.com/image/pic/item/6159252dd42a2834a75bb01156b5c9ea15cebf2f.jpg", ""));
    imageInfoList.add(new ImageInfo(3, "图片2，公告2啦啦啦啦", "", "http://c.hiphotos.baidu.com/image/h%3D300/sign=cfce96dfa251f3dedcb2bf64a4eff0ec/4610b912c8fcc3ce912597269f45d688d43f2039.jpg", ""));
    imageInfoList.add(new ImageInfo(4, "图片3，公告3啦啦啦啦", "", "http://e.hiphotos.baidu.com/image/pic/item/6a600c338744ebf85ed0ab2bd4f9d72a6059a705.jpg", ""));
    imageInfoList.add(new ImageInfo(5, "图片4，公告4啦啦啦啦", "", "http://b.hiphotos.baidu.com/image/h%3D300/sign=8ad802f3801001e9513c120f880e7b06/a71ea8d3fd1f4134be1e4e64281f95cad1c85efa.jpg", ""));
    imageInfoList.add(new ImageInfo(6, "图片5，公告5啦啦啦啦", "", "http://e.hiphotos.baidu.com/image/h%3D300/sign=73443062281f95cab9f594b6f9177fc5/72f082025aafa40fafb5fbc1a664034f78f019be.jpg", ""));
 imageInfoList.add(new ImageInfo(7, "图片1，公告1啦啦啦啦", "", "http://d.hiphotos.baidu.com/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 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 addDots(final LinearLayout linearLayout, Drawable backgount, int number) {
    List 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：

ic_dot_normal.xml：

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。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。