Android ViewPager无限循环实现底部小圆点动态滑动

概述页面拖动到最后一页再向下滑动回复到第一页，第一页向前滑动回到最后一页

页面拖动到最后一页 再向下滑动回复到 第一页，第一页向前滑动回到 最后一页

同时，底部红色小圆点随着页面的滑动距离比例随时改变位置

布局：

<?xml version="1.0" enCoding="utf-8"?> <relativeLayout   xmlns:androID="http://schemas.androID.com/apk/res/androID"   xmlns:tools="http://schemas.androID.com/tools"   androID:layout_wIDth="match_parent"   androID:layout_height="match_parent"   androID:paddingBottom="@dimen/activity_vertical_margin"   androID:paddingleft="@dimen/activity_horizontal_margin"   androID:paddingRight="@dimen/activity_horizontal_margin"   androID:paddingtop="@dimen/activity_vertical_margin"   tools:context="com.lian.vIEwpagertest.MainActivity">    <androID.support.v4.vIEw.VIEwPager     androID:ID="@+ID/vIEwpager"     androID:layout_wIDth="match_parent"     androID:layout_height="match_parent" >   </androID.support.v4.vIEw.VIEwPager>    <TextVIEw     androID:ID="@+ID/tv"     androID:layout_wIDth="wrap_content"     androID:layout_height="wrap_content"     androID:text="内容"     androID:textSize="25sp"     androID:layout_alignParentBottom="true"     androID:layout_centerHorizontal="true"     />    <relativeLayout     androID:ID="@+ID/rl_bottom"     androID:layout_wIDth="wrap_content"     androID:layout_height="wrap_content"     androID:layout_alignParentBottom="true"     androID:layout_centerHorizontal="true"     androID:layout_marginBottom="45dip" >      <linearLayout       androID:ID="@+ID/ll_points"       androID:layout_wIDth="wrap_content"       androID:layout_height="wrap_content"       androID:orIEntation="horizontal" >     </linearLayout>      <VIEw       androID:ID="@+ID/v_redpoint"       androID:layout_wIDth="10dip"       androID:layout_height="10dip"       androID:background="@drawable/red_circle" />   </relativeLayout> </relativeLayout> 

其中red_circle是用shape绘制的红色小圆点

最后的linearLayout实际上是灰色小圆点的容器，在代码中根据数据的长度动态确定数目

代码：

package com.lian.vIEwpagertest;  import androID.os.Bundle; import androID.support.v4.vIEw.PagerAdapter; import androID.support.v4.vIEw.VIEwPager; import androID.support.v7.app.AppCompatActivity; import androID.util.Log; import androID.vIEw.VIEw; import androID.vIEw.VIEwGroup; import androID.vIEw.VIEwTreeObserver; import androID.Widget.ImageVIEw; import androID.Widget.linearLayout; import androID.Widget.relativeLayout; import androID.Widget.TextVIEw;  import java.util.ArrayList; import java.util.List;  public class MainActivity extends AppCompatActivity {    private VIEwPager mVIEwPager;   private TextVIEw mTextVIEw;   private linearLayout mlinearLayout;   private VIEw mVIEw;   private List<ImageVIEw> mDataList;   private int diatance;    @OverrIDe   protected voID onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     initVIEw();     initData();     initEvent();   }    /**    * 初始化数据    */    private voID initData() {     int[] sorce = new int[]{R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d,R.drawable.e};      mDataList = new ArrayList<ImageVIEw>();      for (int i = 0;i < sorce.length;i ++){       ImageVIEw img = new ImageVIEw(getApplicationContext());       img.setimageResource(sorce[i]);       mDataList.add(img);        //添加底部灰点       VIEw v = new VIEw(getApplicationContext());       v.setBackgroundResource(R.drawable.gray_circle);       //指定其大小       linearLayout.LayoutParams params = new linearLayout.LayoutParams(20,20);       if (i != 0)         params.leftmargin = 20;       v.setLayoutParams(params);       mlinearLayout.addVIEw(v);     }      mVIEwPager.setAdapter(new MyAdapter());      //设置每次加载时第一页在MAX_VALUE / 2 - Extra 页，造成用户无限轮播的错觉     int startPage = Integer.MAX_VALUE / 2;     int extra = startPage % mDataList.size();     startPage = startPage - extra;     mVIEwPager.setCurrentItem(startPage);   }    /**    * VIEwPager的容器    */    public class MyAdapter extends PagerAdapter{      @OverrIDe     public int getCount() {       //告诉容器我们的数据长度为Integer.MAX_VALUE，这样就可以一直滚动       return Integer.MAX_VALUE;     }      @OverrIDe     public boolean isVIEwFromObject(VIEw vIEw,Object object) {       return vIEw == object;     }      @OverrIDe     public Object instantiateItem(VIEwGroup container,int position) {       //若position超过mDataList.size()，会发生越界异常，所以这里每次超过size又从0开始计算位置       position = position % mDataList.size();        ImageVIEw img = mDataList.get(position);       container.addVIEw(img);        return img;     }      @OverrIDe     public voID destroyItem(VIEwGroup container,int position,Object object) {        position = position % mDataList.size();        container.removeVIEw((VIEw)object);        // super.destroyItem(container,position,object);     }   }    private voID initEvent() {       /**      * 当底部红色小圆点加载完成时测出两个小灰点的距离，便于计算后面小红点动态移动的距离      */     mVIEw.getVIEwTreeObserver().addOnGlobalLayoutListener(new VIEwTreeObserver.OnGlobalLayoutListener() {       @OverrIDe       public voID onGlobalLayout() {         diatance = mlinearLayout.getChildAt(1).getleft() - mlinearLayout.getChildAt(0).getleft();         Log.d("两点间距",diatance + "测出来了");       }     });      mVIEwPager.setonPagechangelistener(new VIEwPager.OnPagechangelistener() {       @OverrIDe       public voID onPageScrolled(int position,float positionOffset,int positionOffsetPixels) {          //测出页面滚动时小红点移动的距离，并通过setLayoutParams(params)不断更新其位置         position = position % mDataList.size();         float leftmargin = diatance * (position + positionOffset);         relativeLayout.LayoutParams params = (relativeLayout.LayoutParams) mVIEw.getLayoutParams();         params.leftmargin = Math.round(leftmargin);         mVIEw.setLayoutParams(params);         Log.d("红点在这",leftmargin + "");       }        @OverrIDe       public voID onPageSelected(int position) {        }        @OverrIDe       public voID onPageScrollStateChanged(int state) {        }     });   }    private voID initVIEw() {      setContentVIEw(R.layout.activity_main);      mVIEwPager = (VIEwPager) findVIEwByID(R.ID.vIEwpager);      mTextVIEw = (TextVIEw) findVIEwByID(R.ID.tv);      mlinearLayout = (linearLayout) findVIEwByID(R.ID.ll_points);      mVIEw = findVIEwByID(R.ID.v_redpoint);   } } 

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