ViewPager实现图片轮翻效果

很多App都有这种效果，特别一些电商类的App，顶部每隔几秒钟会向右翻页显示下张图片，用来作推广或者内容展示用的。今天来简单地模仿一下，还自带一个自动跳动的小功能（底部有几个小点，图片移动的时候，点的状态也在变化），用定时器来实现不难。

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

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
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.util.Log;
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 {

	protected static final String TAG = "MainActivity";
	private List<ImageView> imageViewList;
	private ViewPager mViewPager;
	private final int[] imageResIDs = {
			R.drawable.a,
			R.drawable.b,
			R.drawable.c,
			R.drawable.d,
			R.drawable.e
	};
	private final String[] imageDescriptions = {
			"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 TextView tvImageDescription;	// 图片描述
	private LinearLayout llPointGroup;		// 点控件的组
	private int previousPosition = 0;		// viewpager选中的前一个position
	private boolean isStop = false;	// 控制循环的子线程是否停止

	private Handler handler = new Handler(){

		@Override
		public void handleMessage(Message msg) {
			super.handleMessage(msg);

			mViewPager.setCurrentItem(mViewPager.getCurrentItem() + 1);
		}
	};

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

        initView();

        new Thread(new Runnable() {

			@Override
			public void run() {
				// 每两秒钟向主线程发送一条消息, 切换viewpager的界面
				while(!isStop) {
					SystemClock.sleep(2000);

					handler.sendEmptyMessage(0);
				}
				Log.i(TAG, "循环线程停止了");
			}}).start();
    }

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

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

		imageViewList = new ArrayList<ImageView>();

		ImageView iv;
		View pointView;
		LayoutParams params;
		for (int i = 0; i < imageResIDs.length; i++) {
			iv = new ImageView(this);
			iv.setBackgroundResource(imageResIDs[i]);
			imageViewList.add(iv);

			// 根据图片添加点
			pointView = new View(this);
			params = new LayoutParams(5, 5);
			params.leftMargin = 5;
			pointView.setLayoutParams(params);
			pointView.setEnabled(false);
			pointView.setBackgroundResource(R.drawable.point_bg);
			llPointGroup.addView(pointView);
		}

		MyPagerAdapter mAdapter = new MyPagerAdapter();
		mViewPager.setAdapter(mAdapter);
		mViewPager.setOnPageChangeListener(this);

		int item = (Integer.MAX_VALUE / 2) - ((Integer.MAX_VALUE / 2) % imageViewList.size());
		mViewPager.setCurrentItem(item);		// 设置当前选中的item的position

		tvImageDescription.setText(imageDescriptions[previousPosition]);
		llPointGroup.getChildAt(previousPosition).setEnabled(true);	// 第一点被选中
	}

	class MyPagerAdapter extends PagerAdapter {

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

		/**
		 * 移动的对象和进来的对象如果是同一个就返回true, 代表复用view对象
		 * false 使用object对象
		 */
		@Override
		public boolean isViewFromObject(View arg0, Object arg1) {
			return arg0 == arg1;
		}

		/**
		 * 需要销毁的对象的position传进来
		 */
		@Override
		public void destroyItem(ViewGroup container, int position, Object object) {
			// 移除掉指定position的对象
			mViewPager.removeView(imageViewList.get(position % imageViewList.size()));
		}

		/**
		 * 加载position位置的view对象
		 */
		@Override
		public Object instantiateItem(ViewGroup container, int position) {
			// 添加指定position的对象
			mViewPager.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

	}

	/**
	 * 当viewpager页面切换时回调
	 * @param position 就是当前显示的page页
	 */
	@Override
	public void onPageSelected(int position) {
		tvImageDescription.setText(imageDescriptions[position % imageViewList.size()]);
		llPointGroup.getChildAt(position % imageViewList.size()).setEnabled(true);
		llPointGroup.getChildAt(previousPosition).setEnabled(false);

		previousPosition = position % imageViewList.size();
	}
}