Android ViewPager不会从屏幕中删除旧视图

Question

我正在尝试向我的应用添加一个页面浏览器，只是显示一些图片来解释应用程序的工作方式，但我遇到了很多问题...... 它正确显示的第一页但是当我拖到下一页时，我刚刚看到的所有页面都停留在后台，这会引起奇怪的可视化。

这是我的代码......

import android.app.Activity;
import android.os.Bundle;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.widget.ImageView;

public class ViewPagerActivity extends Activity {
private static int NUM_VIEWS = 5;

private MyPagerAdapter adapter;
private ViewPager pager;
private int[] pics = { R.drawable.bookmarks, R.drawable.bookmarks_click, R.drawable.help,
        R.drawable.help_click, R.drawable.logo_wil };

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_view_pager);

    adapter = new MyPagerAdapter();
    pager = (ViewPager) findViewById(R.id.mypager);
    pager.setAdapter(adapter);
}

private class MyPagerAdapter extends PagerAdapter {

    @Override
    public int getCount() {
        return NUM_VIEWS;
    }

    /**
     * Create the page for the given position. The adapter is responsible
     * for adding the view to the container given here, although it only
     * must ensure this is done by the time it returns from
     * {@link #finishUpdate()}.
     * 
     * @param container
     *            The containing View in which the page will be shown.
     * @param position
     *            The page position to be instantiated.
     * @return Returns an Object representing the new page. This does not
     *         need to be a View, but can be some other container of the
     *         page.
     */
    @Override
    public Object instantiateItem(View collection, int position) {
        ImageView view = new ImageView(ViewPagerActivity.this);
        view.setImageResource(pics[position]);

        ((ViewPager) collection).addView(view, 0);

        return view;
    }

    /**
     * Remove a page for the given position. The adapter is responsible for
     * removing the view from its container, although it only must ensure
     * this is done by the time it returns from {@link #finishUpdate()}.
     * 
     * @param container
     *            The containing View from which the page will be removed.
     * @param position
     *            The page position to be removed.
     * @param object
     *            The same object that was returned by
     *            {@link #instantiateItem(View, int)}.
     */

    @Override
    public void destroyItem(View collection, int position, Object view) {
        ((ViewPager) collection).removeView((ImageView) view);          
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == ((ImageView) object);
    }

    /**
     * Called when the a change in the shown pages has been completed. At
     * this point you must ensure that all of the pages have actually been
     * added or removed from the container as appropriate.
     * 
     * @param container
     *            The containing View which is displaying this adapter's
     *            page views.
     */
    @Override
    public void finishUpdate(View arg0) {
    }

    @Override
    public void restoreState(Parcelable arg0, ClassLoader arg1) {
    }

    @Override
    public Parcelable saveState() {
        return null;
    }

    @Override
    public void startUpdate(View arg0) {
    }


}

}