Android 使用ViewPager实现轮播图效果

写这篇文章只是对今天所学的知识进行加深印象，对viewpager的一些处理，比如适配器和各个方法的作用等。

先看效果图

这里我是在xml中写的圆点

drawable文件夹下的xml代码：

shape_yes.xml:

<?xml version="1.0" encoding="utf-8"?> 
<shape xmlns:android="http://schemas.android.com/apk/res/android"> 
  <solid android:color="#ff6c67"></solid> 
  <corners android:radius="1000dp"></corners> 
</shape>

shape_no.xml:

<?xml version="1.0" encoding="utf-8"?> 
<shape xmlns:android="http://schemas.android.com/apk/res/android"> 
<solid android:color="#f0f0f0"></solid> 
  <corners android:radius="1000dp"></corners> 
</shape>

选择器

<?xml version="1.0" encoding="utf-8"?> 
<selector xmlns:android="http://schemas.android.com/apk/res/android"> 
<item android:drawable="@drawable/shape_no" 
  android:state_selected="false" 
  /> 
  <item android:drawable="@drawable/shape_yes" 
   android:state_selected="true" 
    /> 
</selector> 

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?> 
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent"> 
  <relativelayout 
    android:layout_width="match_parent" 
    android:layout_height="160dp"> 
    <android.support.v4.view.viewpager 
      android:id="@+id/vp" 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content"> 
    </android.support.v4.view.viewpager> 
    <linearlayout 
      android:layout_width="match_parent" 
      android:layout_height="40dp" 
      android:layout_alignparentbottom="true" 
      android:gravity="center_horizontal" 
      android:padding="5dp" 
      android:orientation="vertical" 
      android:background="#66000000"> 
      <linearlayout 
        android:layout_width="match_parent" 
        android:layout_height="wrap_content" 
        android:layout_gravity="bottom" 
        android:gravity="center" 
        android:orientation="horizontal" 
        android:paddingbottom="10dp"> 
        <imageview 
          android:id="@+id/iv_one" 
          android:layout_width="20dp" 
          android:layout_height="20dp" 
          android:layout_marginright="20dp" 
          android:background="@drawable/selector_show" /> 
        <imageview 
          android:id="@+id/iv_two" 
          android:layout_width="20dp" 
          android:layout_height="20dp" 
          android:layout_marginright="20dp" 
          android:background="@drawable/selector_show" /> 
        <imageview 
          android:id="@+id/iv_three" 
          android:layout_width="20dp" 
          android:layout_height="20dp" 
          android:background="@drawable/selector_show" /> 
      </linearlayout> 
    </linearlayout> 
  </relativelayout> 
</relativelayout> 

写一个类viewpageradapter_circleextends pageradapter

public class viewpageradapter_circle extends pageradapter { 
  arraylist<view> arraylist; 
  context context; 
  public viewpageradapter_circle(arraylist<view> arraylist, context context) { 
    this.arraylist = arraylist; 
    this.context = context; 
  } 
  /***数据源的大小（条目）*/ 
  @override 
  public int getcount() { 
    return arraylist.size(); 
  } 
  /** 
   * 页面视图是否关联到特定的对象 
   */ 
  @override 
  public boolean isviewfromobject(view view, object object) { 
    return view == object;//判断当前要显示的页面 
  } 
  /** 
   * 初始化页面 
   * 1.页面添加到container 
   * 2.将页面返回 
   */ 
  @override 
  public object instantiateitem(viewgroup container, int position) { 
    container.addview(arraylist.get(position));//页面添加到container，添加位置 
    return arraylist.get(position); 
  } 
  /** 
   * 销毁当前页面 
   */ 
  @override 
  public void destroyitem(viewgroup container, int position, object object) { 
    container.removeview(arraylist.get(position)); 
  } 
} 

mainactivity中代码（含注解）

public class mainactivity extends appcompatactivity { 
  viewpager viewpager; 
  int imageresids[]; 
  arraylist<view> imageviewlist;//存图片的集合 
  arraylist<imageview> imageviews;//存白点的集合 
  imageview iv_one,iv_two,iv_three; 
  int oldpostion;//记录原来的位置 
  private boolean flag; 
  int count=0; 
  handler handler = new handler() { 
    @override 
    public void handlemessage(message msg) { 
      super.handlemessage(msg); 
      if (msg.what == 0) { 
        viewpager.setcurrentitem(count); 
      } 
    } 
  }; 
  @override 
  protected void oncreate(bundle savedinstancestate) { 
    super.oncreate(savedinstancestate); 
    setcontentview(r.layout.activity_main); 
    //初始化布局 
    initview(); 
    //初始化数据 
    initdata(); 
    //设置适配器 
    initadapter(); 
    //设置圆点 
    initpoint(); 
    flag = true; 
//循环设置播放 
    new thread() { 
      @override 
      public void run() { 
        while (flag) { 
          try { 
            thread.sleep(3000); 
            count++; 
            if (count == 3) { 
              count = 0; 
            } 
          } catch (interruptedexception e) { 
            e.printstacktrace(); 
          } 
          /**传递信息*/ 
          message msg = new message(); 
          msg.what = 0; 
          msg.obj = count; 
          handler.sendmessage(msg); 
        } 
      } 
    }.start(); 
  } 
  private void initview() { 
    viewpager = (viewpager) findviewbyid(r.id.vp); 
  } 
  //初始化要显示的数据 
  private void initdata() { 
    //图片资源数组 
    imageresids = new int[]{r.mipmap.a, r.mipmap.b, r.mipmap.c}; 
    imageviewlist = new arraylist<>();//存图片的集合 
    imageview imageview; 
    for (int i = 0; i < imageresids.length; i++) { 
      imageview = new imageview(this); 
      imageview.setbackgroundresource(imageresids[i]); 
      imageviewlist.add(imageview); 
    } 
  } 
  //设置适配器 
  private void initadapter() { 
    viewpageradapter_circle myviewpageradapter = new viewpageradapter_circle(imageviewlist, this); 
    viewpager.setadapter(myviewpageradapter); 
  } 
  /** 
   * 设置圆点的 
   */ 
  private void initpoint() { 
    iv_one = (imageview) findviewbyid(r.id.iv_one); 
    iv_two = (imageview) findviewbyid(r.id.iv_two); 
    iv_three = (imageview) findviewbyid(r.id.iv_three); 
    imageviews = new arraylist<>(); 
    imageviews.add(iv_one); 
    imageviews.add(iv_two); 
    imageviews.add(iv_three); 
    iv_one.setselected(true);//设置第一个圆点为true 
    /**viewpager监听事件*/ 
    viewpager.addonpagechangelistener(new viewpager.onpagechangelistener() { 
      /**滑动时调用*/ 
      @override 
      public void onpagescrolled(int position, float positionoffset, int positionoffsetpixels) { 
      } 
      /**停止时调用*/ 
      @override 
      public void onpageselected(int position) { 
        imageviews.get(position).setselected(true);//滑动后颜色改变 
        imageviews.get(oldpostion).setselected(false);//变为初始颜色 
        oldpostion = position;//把滑动后的圆点的position给原来的oldpostion 
      } 
        /**滑动状态改变时调用*/ 
      @override 
      public void onpagescrollstatechanged(int state) { 
      } 
    }); 
  } 
} 

以上所述是小编给大家介绍的android 使用viewpager实现轮播图效果，希望对大家有所帮助