Android ViewPager 小圆点 + 无限循环 + 动态滑动

• 前言

  最近的一个项目需要用到这种效果, 所以今天我们来实现这个ViewPager+小圆点+无限循环,这种效果可以用来作首页的广告啊, 各种显示图片的地方都就可以.

• ViewPager.OnPageChangeListener

  我们知道ViewPager有一个方法是经常用到的, 就是 onPageChangeListener(…) ,这个方法是用来监听Viewpager滑动的, 所以我们要加小圆点就需要自己实现这个方法.

  代码如下:

      public class DetailsPhotoPagerListener implements ViewPager.OnPageChangeListener {
          private Context mContext;
          private LinearLayout mLinearLayout;         //底部圆点布局
          private int mSize;                          //圆点数量
          private List mDotView;           //圆点容器
  
          public DetailsPhotoPagerListener(Context context, LinearLayout linearLayout, int size) {
              mContext = context;
              mLinearLayout = linearLayout;
              mSize = size;
              initData();
          }
  
          private void initData() {
              mDotView=new ArrayList<>();
              for (int i = 0; i < mSize; i++) {
                  ImageView imageView = new ImageView(mContext);
                  LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                  params.leftMargin = 10;     //设置圆点相距距离
                  params.rightMargin = 10;
                  if (i == 0) {               //初始化为红点
                      imageView.setBackgroundResource(R.drawable.bg_details_photo_viewindicator_red);
                  } else {
                      imageView.setBackgroundResource(R.drawable.bg_details_photo_viewindicator_grey);
                  }
                  mLinearLayout.addView(imageView,params);
                  mDotView.add(imageView);
              }
          }
  
          @Override
          public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
  
          }
  
          @Override
          public void onPageSelected(int position) {
              for (int i = 0; i < mSize; i++) {
                  if ((position % mSize) == i) {      //如果是当前的位置就设置为红点
                      mDotView.get(i).setBackgroundResource(R.drawable.bg_details_photo_viewindicator_red);
                  } else {
                      mDotView.get(i).setBackgroundResource(R.drawable.bg_details_photo_viewindicator_grey);
                  }
              }
          }
  
          @Override
          public void onPageScrollStateChanged(int state) {
  
          }
      }
  

  道理很简单, 这里的小圆点我是在Drawable里新建一个shape类型画的, 也很简单,还是贴一下吧

  
      <selector xmlns:android="http://schemas.android.com/apk/res/android">
          <item>
              <shape android:shape="oval" android:useLevel="false">
  
                  <solid android:color="@color/color_primary"/>
                  <size android:width="8dp" android:height="8dp"/>
              shape>
          item>
      selector>

• 无限循环滑动

  就是ViewPagerAdapter里面设置一下%, 跟哈希表一样, 循环一下,很简单, 代码如下.

  public class DetailsPhotoPageAdapter extends PagerAdapter {
      private List mPhoto;
      private Context mContext;
      private int mSize;
  
      public DetailsPhotoPageAdapter(Context context, List photo) {
          mPhoto = photo;
          mContext = context;
          mSize = mPhoto.size();
      }
  
      @Override
      public int getCount() {
          return Integer.MAX_VALUE;   //实现无限滑动
      }
  
      @Override
      public boolean isViewFromObject(View view, Object object) {
          return view == object;
      }
  
      @Override
      public Object instantiateItem(ViewGroup container, int position) {
          position = position % mSize;        //永远不越界
          View view = LayoutInflater.from(mContext).inflate(R.layout.viewpager_details_top, null);
          ImageView imageView = (ImageView) view.findViewById(R.id.iv_details_top);
          Glide.with(mContext).load(mPhoto.get(position)).into(imageView);
          container.addView(view);
          return view;
      }
  
      @Override
      public void destroyItem(ViewGroup container, int position, Object object) {
          container.removeView((View) object);
      }
  }

  最后别忘了在初始化的时候, 设置加入以下代码, 让人以为是无限循环, 不加的话第一张不能向左滑动

         int startPage = Integer.MAX_VALUE / 2;
         mVpDetailsTop.setCurrentItem(startPage);

  最后再贴一下布局代码吧

  
  <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="wrap_content">
  
              <android.support.v4.view.ViewPager
                  android:id="@+id/vp_details_top"
                  android:layout_width="match_parent"
                  android:layout_height="180dp"
                  >
              android.support.v4.view.ViewPager>
  
              <LinearLayout
                  android:id="@+id/ll_details_top_dot"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:gravity="center"
                  android:layout_gravity="bottom"
                  android:orientation="horizontal"
                  android:layout_marginBottom="5dp">
              LinearLayout>
          FrameLayout>

• 最终效果

---

• 小圆点动态滑动

  看了上面的介绍, 这是最简单的实现小圆点, 但是我们想要酷一点的效果就可以接着看下面.

  1. 首先要改的是布局, 布局增加一个View 然 放在后把他们同一个布局里面, 代码如下:

     <FrameLayout
             android:layout_width="match_parent"
             android:layout_height="wrap_content">
     
             <android.support.v4.view.ViewPager
                 android:id="@+id/vp_details_top"
                 android:layout_width="match_parent"
                 android:layout_height="180dp"
                 >
             android.support.v4.view.ViewPager>
     
             <RelativeLayout
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:layout_gravity="bottom|center"
                 android:layout_marginBottom="5dp">
                 <LinearLayout
                     android:id="@+id/ll_details_top_dot"
                     android:layout_width="wrap_content"
                     android:layout_height="wrap_content"
                     android:orientation="horizontal">
                 LinearLayout>
     
                 <View
                     android:id="@+id/view_details_top_dot_red"
                     android:layout_width="8dp"
                     android:layout_height="8dp"
                     android:background="@drawable/bg_details_photo_viewindicator_red"
                     />
     
             RelativeLayout>
     
     
         FrameLayout>

  2. 然后是OnPageChangeListener

     public class DetailsPhotoPagerListener implements ViewPager.OnPageChangeListener {
         private Context mContext;
         private LinearLayout mLinearLayout;         //底部圆点布局
         private int mSize;                          //圆点数量
         private List mDotView;           //圆点容器
         private float mDistance;
         private View mView;
         RelativeLayout.LayoutParams mViewParams;
     
         public DetailsPhotoPagerListener(Context context, LinearLayout linearLayout, View view, int size) {
             mContext = context;
             mLinearLayout = linearLayout;
             mSize = size;
             mView = view;
             initData();
         }
     
         private void initData() {
             mDotView = new ArrayList<>();
             for (int i = 0; i < mSize; i++) {
                 ImageView imageView = new ImageView(mContext);
                 LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
                 imageView.setBackgroundResource(R.drawable.bg_details_photo_viewindicator_grey);
                 if (i != 0) {
                     params.leftMargin = 10;     //设置圆点相距距离
                 }
                 mLinearLayout.addView(imageView, params);
                 mDotView.add(imageView);
             }
               //以下为修改的主要代码
             mViewParams = (RelativeLayout.LayoutParams) mView.getLayoutParams();
             mView.post(new Runnable() {     //获得两个点之间的距离
                 @Override
                 public void run() {
                     mDistance = mLinearLayout.getChildAt(1).getLeft() - mLinearLayout.getChildAt(0).getLeft();
                 }
             });
     
     
         }
     
         @Override
         public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
             position = position % mSize;
             float leftMargin = 0;
             if (position != mSize - 1) {                                    //如果是在最后一页, 往右滑就不增加滑动距离
                 leftMargin = mDistance * (position + positionOffset);
             } else {
                 leftMargin = mDistance * position;
             }
             if(mViewParams!=null){
                 mViewParams.leftMargin = Math.round(leftMargin);
                 mView.setLayoutParams(mViewParams);
             }
         }
     
         @Override
         public void onPageSelected(int position) {
     
         }
     
         @Override
         public void onPageScrollStateChanged(int state) {
     
         }
     }

     主要修改的地方还是在滑动监听的地方, 上面的注释也解释得挺清楚的.

  3. 最终效果