Android中 ViewPager的使用

<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"
    tools:context="com.example.demo_viewpager.MainActivity$PlaceholderFragment" >

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="fill_parent"
        android:layout_height="200dip"/>
    <LinearLayout 
        android:layout_alignBottom="@id/viewpager"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="#33000000"
        android:orientation="vertical">
        
        <TextView 
            android:id="@+id/tv_image_description"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="@android:color/white"
            android:layout_gravity="center"/>
        <LinearLayout 
            android:id="@+id/ll_point_group"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:layout_marginTop="5dip"
            android:layout_marginBottom="5dip"
            android:layout_gravity="center_horizontal"></LinearLayout>
    </LinearLayout>

</RelativeLayout>

public class MainActivity extends Activity implements OnPageChangeListener {

    private List<ImageView> imageviewlist;
    private TextView tv_Description;
    private LinearLayout llPointGroup;
    private int previousEnablePosition = 0; // 前一个被选中的点的索引

    private String[] imageDiscriptionArray = { "托普早上好", "托普中午好", "托普下午好",
            "托普晚上好", "托普深夜好" };
    private boolean isStop = false;        // 是否停止子线程, 不会停止
    private ViewPager viewpager;
    
    @Override
    protected void onDestroy() {
        isStop = true;
        super.onDestroy();
    }
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.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
                            viewpager.setCurrentItem(viewpager.getCurrentItem() + 1);
                        }
                    });
                }
            }
        });
        mThread.start();

    }

    private void Init() {
        ImageView iv;
        View view;
        LayoutParams params;
        viewpager = (ViewPager) findViewById(R.id.viewpager);
        llPointGroup = (LinearLayout) findViewById(R.id.ll_point_group);
        tv_Description = (TextView) findViewById(R.id.tv_image_description);
        imageviewlist = new ArrayList<ImageView>();
        int[] imageresid = { R.drawable.img1, R.drawable.img2, R.drawable.img3,
                R.drawable.img4, R.drawable.img5 };
        for (int id : imageresid) {
            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(10, 10);
            params.leftMargin = 10;
            view.setEnabled(false);
            view.setLayoutParams(params);
            llPointGroup.addView(view);// 向线性布局中添加点
        }
        viewpager.setAdapter(new MyAdapter());
        viewpager.setOnPageChangeListener(this);

        // 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());
        viewpager.setCurrentItem(index); // 设置当前的默认索引
    }

    class MyAdapter extends PagerAdapter {

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

        /**
         * View当前显示的ImageView,Object 可能是ImageView或下一个ImageView 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 positon
         *            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) {
            container
                    .addView(imageviewlist.get(position % imageviewlist.size()));
            return imageviewlist.get(position % imageviewlist.size());
        }

    }

    @Override
    public void onPageScrollStateChanged(int arg0) {
        

    }

    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {
        

    }

    @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
        tv_Description.setText(imageDiscriptionArray[newPosition]);

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

        // 根据索引设置被选中的点
        llPointGroup.getChildAt(newPosition).setEnabled(true);

        previousEnablePosition = newPosition;
    }

}