怎么实现类似Path、海豚浏览器、人人那样的横向侧滑导航栏？求解

/**
 * 包裹在该布局内部的子视图可以左右滑动<br>
 * @author http://blog.csdn.net/Yao_GUET date: 2011-05-04
 */
public class HorizonalScrollLayout extends LinearLayout {
    
    /**
     * 通过Handler将滑屏结果通知使用该滑屏控件的Activity<br>
     * 必须先调用<br><code>public void setHandler(Handler handler) </code><br>来设置handler.返回的消息为:<br>
     * <code>
     * Message msg = new Message();<br>
        msg.what = ON_SCROLL_CHANGED_MESSAGE_WHAT;<br>
        msg.arg1 = whichScreen;//滑到的目标屏幕索引（0为第一个屏幕）<br>
        handler.sendMessage(msg);<br>
     * 
     * </code>
     */
    public static final int ON_SCROLL_CHANGED_MESSAGE_WHAT = 2087;

    private static final String TAG = "HorizonalScrollLayout";
    private Scroller mScroller;
    private VelocityTracker mVelocityTracker;

    private int mCurScreen;
    private int mDefaultScreen = 0;

    private static final int TOUCH_STATE_REST = 0;
    private static final int TOUCH_STATE_SCROLLING = 1;

    private static final int SNAP_VELOCITY = 600;

    private int mTouchState = TOUCH_STATE_REST;
    private int mTouchSlop;
    private float mLastMotionX;
    private float mLastMotionY;
    
    private OnSnapDestinationListener onSnapDestinationListener;
    
    
    Handler handler ;


    public HorizonalScrollLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        mScroller = new Scroller(context);

        mCurScreen = mDefaultScreen;
        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
//        if (changed) { //如果不注释掉，里面的ListView显示出不来
            int childLeft = 0;
            final int childCount = getChildCount();

            for (int i = 0; i < childCount; i++) {
                final View childView = getChildAt(i);
                if (childView.getVisibility() != View.GONE) {
                    final int childWidth = childView.getMeasuredWidth();
                    childView.layout(childLeft, 0, childLeft + childWidth, childView
                            .getMeasuredHeight());
                    childLeft += childWidth;
                }
            }
//        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        final int width = MeasureSpec.getSize(widthMeasureSpec);
        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        if (widthMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException("ScrollLayout only canmCurScreen run at EXACTLY mode!");
        }

        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        if (heightMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException("ScrollLayout only can run at EXACTLY mode!");
        }

        // The children are given the same width and height as the scrollLayout
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
        }
        // Log.e(TAG, "moving to screen "+mCurScreen);
        scrollTo(mCurScreen * width, 0);
    }
    
    public void setOnSnapDestinationListener(OnSnapDestinationListener onSnapDestinationListener) {
        this.onSnapDestinationListener = onSnapDestinationListener;
    }

    /**
     * According to the position of current layout scroll to the destination
     * page.
     */
    public void snapToDestination() {
        final int screenWidth = getWidth();
        final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
        snapToScreen(destScreen);
    }

    public void snapToScreen(int whichScreen) {
        int tmp = mCurScreen;
        // get the valid layout page
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        if (getScrollX() != (whichScreen * getWidth())) {
            final int delta = whichScreen * getWidth() - getScrollX();
            mScroller.startScroll(getScrollX(), 0, delta, 0, Math.abs(delta));
            mCurScreen = whichScreen;
            invalidate(); // Redraw the layout
        }
        if(tmp == whichScreen){
            return;
        }
        if(handler!= null){
            Message msg = new Message();
            msg.what = ON_SCROLL_CHANGED_MESSAGE_WHAT;
            msg.arg1 = whichScreen;
            handler.sendMessage(msg);
        }
    }

    public void setToScreen(int whichScreen) {
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        mCurScreen = whichScreen;
        scrollTo(whichScreen * getWidth(), 0);
        invalidate();
    }

    public int getCurScreen() {
        return mCurScreen;
    }

    @Override
    public void computeScroll() {
        if (mScroller.computeScrollOffset()) {
            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
            postInvalidate();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (mVelocityTracker == null) {
            mVelocityTracker = VelocityTracker.obtain();
        }
        mVelocityTracker.addMovement(event);

        final int action = event.getAction();
        final float x = event.getX();
        final float y = event.getY();

        switch (action) {
        case MotionEvent.ACTION_DOWN:
//            Log.e(TAG, "event down!");
            if (!mScroller.isFinished()) {
                mScroller.abortAnimation();
            }
            mLastMotionX = x;
            break;

        case MotionEvent.ACTION_MOVE:
            int deltaX = (int) (mLastMotionX - x);
            mLastMotionX = x;

            scrollBy(deltaX, 0);
            break;

        case MotionEvent.ACTION_UP:
//            Log.e(TAG, "event : up");
            // if (mTouchState == TOUCH_STATE_SCROLLING) {
            final VelocityTracker velocityTracker = mVelocityTracker;
            velocityTracker.computeCurrentVelocity(1000);
            int velocityX = (int) velocityTracker.getXVelocity();

//            Log.e(TAG, "velocityX:" + velocityX);

            if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
                // Fling enough to move left
//                Log.e(TAG, "snap left");
                if(onSnapDestinationListener == null || onSnapDestinationListener.isAbleToSnap())
                    snapToScreen(mCurScreen - 1);
                else 
                    snapToScreen(mCurScreen);
            } else if (velocityX < -SNAP_VELOCITY && mCurScreen < getChildCount() - 1) {
                // Fling enough to move right
//                Log.e(TAG, "snap right");
                if(onSnapDestinationListener == null || onSnapDestinationListener.isAbleToSnap())
                    snapToScreen(mCurScreen + 1);
                else 
                    snapToScreen(mCurScreen);
            } else {
                snapToDestination();
            }

            if (mVelocityTracker != null) {
                mVelocityTracker.recycle();
                mVelocityTracker = null;
            }
            // }
            mTouchState = TOUCH_STATE_REST;
            break;
        case MotionEvent.ACTION_CANCEL:
            mTouchState = TOUCH_STATE_REST;
            break;
        }

        return true;
    }
    
    public void setHandler(Handler handler) {
        this.handler = handler;
    }
    

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
//        Log.e(TAG, "onInterceptTouchEvent-slop:" + mTouchSlop);

        final int action = ev.getAction();
        if ((action == MotionEvent.ACTION_MOVE) && (mTouchState != TOUCH_STATE_REST)) {
            return true;
        }

        final float x = ev.getX();
        final float y = ev.getY();

        switch (action) {
        case MotionEvent.ACTION_MOVE:
            
            /*
             * 2011.12.29 
             * 如果内部的子视图有ScrollView，当用户在ScrollView上下滑动的时候，判断如果Y轴变化值大于X轴变化的1.2倍，就不要消费这个事件了
             * 否则会导致用户本来是想上下滑动ScrollView 结果这个滑动事件被本视图吸收了，变为左右滑动
             */
            int deltaX = (int) (mLastMotionX - x);
            int deltaY = (int) (mLastMotionY - y);
            if(Math.abs(deltaY) > Math.abs(deltaX * 1.2)){
                return false;
            }
            /*
             * =========================================
             */
            
            final int xDiff = (int) Math.abs(mLastMotionX - x);
            if (xDiff > mTouchSlop) {
                mTouchState = TOUCH_STATE_SCROLLING;
            }
            break;
        case MotionEvent.ACTION_DOWN:
            mLastMotionX = x;
            mLastMotionY = y;
            mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;
            break;

        case MotionEvent.ACTION_CANCEL:
        case MotionEvent.ACTION_UP:
            mTouchState = TOUCH_STATE_REST;
            break;
        }

        return mTouchState != TOUCH_STATE_REST;
    }
    
    public interface OnSnapDestinationListener{
        
        /**
         * 当滑到目标屏幕的时间发生之前调用，如果返回false；则不继续
         * @return
         * @author : wang.jun<br>
         * @time : Mar 12, 2012 4:17:24 PM<br>
         */
        public boolean isAbleToSnap();
        
    }

}