android viewpager实现竖直滑动效果

public class CustomViewPager extends ViewGroup {
 private static final String TAG = CustomViewPager.class.getSimpleName();
 private float startX = 0;
 private GestureDetector detector;
 int a = 30;
 public CustomViewPager(Context context, AttributeSet attrs, int defStyle) {
 super(context, attrs, defStyle);
 }
 
 public CustomViewPager(Context context, AttributeSet attrs) {
 super(context, attrs);
 init(context);
 }
 private void init(Context context) {
 detector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener(){
 /**
 * distanceX 在屏幕上要移动的距离 而不是坐标
 */
 @Override
 public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
 scrollBy(0, (int)distanceY);
 return true;
 }
 });
 }
 public CustomViewPager(Context context) {
 super(context);
 }
 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {
 for(int i=0;i<getChildCount();i++){
 View childView = getChildAt(i);
// childView.layout(i*getWidth(), 0, (i+1)*getWidth(), getHeight());、//这是水平方向滑动
 childView.layout(0, i*getHeight(), getWidth(), (i+1)*getHeight());//这是竖直方向滑动
 }
 }
 /**
 * 这个默认super.onTouchEvent(event)为false
 */
 @Override
 public boolean onTouchEvent(MotionEvent event) {
 detector.onTouchEvent(event);
 return true;
 }
}

public class MainActivity extends ActionBarActivity {
 private CustomViewPager custom_view_pager;
 private int[] ids = {R.drawable.a1,R.drawable.a2,R.drawable.a3,R.drawable.a4,R.drawable.a5,R.drawable.a6};
 private List<ImageView> imageViews;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 DisplayUtil.init(this);
 custom_view_pager = (CustomViewPager) findViewById(R.id.custom_view_pager);
 initData();
 }
 private void initData() {
 imageViews = new ArrayList<>();
 for(int i=0;i<ids.length;i++){
 ImageView imageView = new ImageView(this);
 imageView.setBackgroundResource(ids[i]);
 imageViews.add(imageView);
 custom_view_pager.addView(imageView);
 }
 }
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 >
 <zhi.more.customviewpager.view.CustomViewPager
  android:id="@+id/custom_view_pager"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
   />
</RelativeLayout>