viewpage广告条的制作

 package com.itheima27.viewpagerdemo;

 import java.util.ArrayList;
 import java.util.List;

 import android.app.Activity;
 import android.os.Bundle;
 import android.os.SystemClock;
 import android.support.v4.view.PagerAdapter;
 import android.support.v4.view.ViewPager;
 import android.support.v4.view.ViewPager.OnPageChangeListener;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.ImageView;
 import android.widget.LinearLayout;
 import android.widget.LinearLayout.LayoutParams;
 import android.widget.TextView;

 public class MainActivity extends Activity implements OnPageChangeListener {

     private List<ImageView> imageViewList;
     private TextView tvDescription;
     private LinearLayout llPointGroup;
     private int previousEnabledPosition = 0;        // 前一个被选中的"点"的索引, 默认情况下: 0

     private String[] imageDescriptionArray = {
             "巩俐不低俗，我就不能低俗",
             "扑树又回来啦！再唱经典老歌引万人大合唱",
             "揭秘北京电影如何升级",
             "乐视网TV版大派送",
             "热血屌丝的反杀"
     };
     private ViewPager mViewPager;

     private boolean isStop = false;        // 是否停止子线程, 不会停止

     @Override
     protected void onDestroy() {
         isStop = true;
         super.onDestroy();
     }

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         init();

         // 开启线程无限自动移动
         Thread mThread = new Thread(new Runnable() {
             @Override
             public void run() {
                 while(!isStop) {
                     // 每隔2秒钟, 发送一条消息到主线程, 更新viewpager的界面
                     SystemClock.sleep(2000);

                     runOnUiThread(new Runnable() {
                         @Override
                         public void run() {
                             // 此方法是在主线程中执行
                             mViewPager.setCurrentItem(mViewPager.getCurrentItem() + 1);
                         }
                     });
                 }
             }
         });
         mThread.start();
     }

     private void init() {
         mViewPager = (ViewPager) findViewById(R.id.viewpager);
         llPointGroup = (LinearLayout) findViewById(R.id.ll_point_group);
         tvDescription = (TextView) findViewById(R.id.tv_image_description);

         imageViewList = new ArrayList<ImageView>();

         int[] imageResIDs = {
                 R.drawable.a,
                 R.drawable.b,
                 R.drawable.c,
                 R.drawable.d,
                 R.drawable.e
         };

         ImageView iv;
         View view;
         LayoutParams params;
         for (int id : imageResIDs) {
             iv = new ImageView(this);
             iv.setBackgroundResource(id);
             imageViewList.add(iv);

             // 每循环一次, 添加一个点到Linearlayout中
             view = new View(this);
             view.setBackgroundResource(R.drawable.point_background);
             params = new LayoutParams(5, 5);
             params.leftMargin = 5;
             view.setEnabled(false);
             view.setLayoutParams(params);

             llPointGroup.addView(view);        // 向线性布局中添加"点"
         }

         mViewPager.setAdapter(new MyAdapter());
         mViewPager.setOnPageChangeListener(this);

         // 初始化图片描述, 和哪一个点被选中
 //        tvDescription.setText(imageDescriptionArray[0]);
 //        llPointGroup.getChildAt(0).setEnabled(true);

         // 初始化ViewPager的默认position为Integer.Max_value的一半
         int index = (Integer.MAX_VALUE / 2) - (Integer.MAX_VALUE / 2 % imageViewList.size());
         mViewPager.setCurrentItem(index);        // 设置当前viewpager选中的pager页, 会触发OnPageChangeListener.onPagerSelected

     }

     class MyAdapter extends PagerAdapter {

         @Override
         public int getCount() {
             return Integer.MAX_VALUE;
         }

         /**
          * 复用对象.
          * true 复用对象
          * false 用的是object
          */
         @Override
         public boolean isViewFromObject(View arg0, Object arg1) {
             return arg0 == arg1;
         }

         /**
          * 销毁对象
          * @param position 将要被销毁对象的索引位置
          */
         @Override
         public void destroyItem(ViewGroup container, int position, Object object) {
             container.removeView(imageViewList.get(position % imageViewList.size()));
         }

         /**
          * 初始化一个view对象
          * @param position 将要被创建的对象的索引位置
          */
         @Override
         public Object instantiateItem(ViewGroup container, int position) {
             // 先把对象添加到viewpager中, 再返回当前对象
             container.addView(imageViewList.get(position % imageViewList.size()));
             return imageViewList.get(position % imageViewList.size());
         }
     }

     @Override
     public void onPageScrollStateChanged(int arg0) {
         // TODO Auto-generated method stub

     }

     @Override
     public void onPageScrolled(int arg0, float arg1, int arg2) {
         // TODO Auto-generated method stub

     }

     @Override
     public void onPageSelected(int position) {

         // 取余后的索引
         int newPosition = position % imageViewList.size();

         // 根据索引设置图片的描述
         tvDescription.setText(imageDescriptionArray[newPosition]);

         // 把上一个点设置为未选中
         llPointGroup.getChildAt(previousEnabledPosition).setEnabled(false);

         // 根据索引设置哪一个点被选中
         llPointGroup.getChildAt(newPosition).setEnabled(true);

         previousEnabledPosition = newPosition;
     }
 }