让scrollview在滚动的过程中自动定位页的边边

/**
 * The Class PageScrollView, we can scroll the pages in this component.
 */
public class PageScrollView extends LinearLayout {

    /** The context. */
    private Context mContext;
    
    /** The adapter used to get the view of each page. */
    private BaseAdapter mAdapter;
    
    /** The page count. */
    private int mPageCount = 0;
    
    /** The current page index. */
    private int mCurrPageIndex = 0;
    
    /** The scroll view in this component. */
    private HorizontalScrollView mScrollView;
    
    /** The target parent view for each page. */
    private LinearLayout mPageContent;
    
    /** The velocity tracker. */
    private VelocityTracker mVelocityTracker;
    
    /** The width for each page. */
    private int mWidth;
    
    /** The maximum velocity. */
    private int mMaximumVelocity;
    
    /** The change. */
    private boolean mChange = false;
    
    /** The Constant SNAP_VELOCITY. */
    private static final int SNAP_VELOCITY = 500;
    
    /** The Constant PAGE_FACTOR. */
    private static final int PAGE_FACTOR = 3;

    /** The units parameter for velocity. */
    private static final int VELOCITY_UNITS = 1000;

    /**
     * Instantiates a new page scroll view.
     *
     * @param context the context
     */
    public PageScrollView(Context context) {
        super(context);
        mContext = context;
    }

    /**
     * Instantiates a new page scroll view.
     *
     * @param context the context
     * @param attrs the attrs
     */
    public PageScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mContext = context;
    }

    /**
     * Sets the adapter.
     *
     * @param adapter the adapter
     * @param with the with for each page
     */
    public void setAdapter(BaseAdapter adapter, int with) {
        if (adapter == null) {
            return;
        }

        mAdapter = adapter;
        mWidth = with;
        initUI();
        bindLayoutUI();
    }

    /**
     * Inits the ui.
     */
    private void initUI() {
        this.removeAllViews();

        mScrollView = new HorizontalScrollView(mContext);
        mScrollView.setHorizontalScrollBarEnabled(false);
        mScrollView.setLayoutParams(new ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.FILL_PARENT,
                ViewGroup.LayoutParams.FILL_PARENT));

        mPageContent = new LinearLayout(mContext);
        mPageContent.setLayoutParams(new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.FILL_PARENT,
                LinearLayout.LayoutParams.FILL_PARENT));
        //mPageContent.setGravity(Gravity.CENTER);
        mPageContent.setOrientation(HORIZONTAL);

        mScrollView.setOnTouchListener(mTouchListener);
        this.addView(mScrollView);
        mScrollView.addView(mPageContent);

        // FIXME: width is a problem sometimes!
        final LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams) this.getLayoutParams();
        if (!(lp.width == LinearLayout.LayoutParams.FILL_PARENT
                || lp.width == LinearLayout.LayoutParams.WRAP_CONTENT)) {
            mWidth = lp.width;
        }

        final ViewConfiguration configuration = ViewConfiguration.get(mContext);
        mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
    }

    /**
     * Bind layout ui, add pages to this component.
     */
    private void bindLayoutUI() {
        mPageCount = mAdapter.getCount();

        final LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                mWidth, LinearLayout.LayoutParams.FILL_PARENT);
       // params.gravity = Gravity.CENTER;
        for (int i = 0; i < mPageCount; i++) {
            final View v = mAdapter.getView(i, null, null);
            mPageContent.addView(v, params);
        }
    }

    /**
     * Gets the current page index.
     *
     * @return the current page index
     */
    public int getCurrentPageIndex() {
        return mCurrPageIndex;
    }

    /** The m touch listener. */
    private View.OnTouchListener mTouchListener = new View.OnTouchListener() {

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            final int action = event.getAction();

            if (mVelocityTracker == null) {
                mVelocityTracker = VelocityTracker.obtain();
            }
            mVelocityTracker.addMovement(event);

            switch (action) {
            case MotionEvent.ACTION_UP: 

                final VelocityTracker velocityTracker = mVelocityTracker;
                    velocityTracker.computeCurrentVelocity(VELOCITY_UNITS, mMaximumVelocity);
                    final int velocityX = (int) velocityTracker.getXVelocity();
                    final int scrollX = mScrollView.getScrollX();
                    final int deltaX = (int) (scrollX - mCurrPageIndex * mWidth);
                    if (((velocityX > SNAP_VELOCITY) || (deltaX < -mWidth / PAGE_FACTOR))
                            && mCurrPageIndex > 0) {
                        mCurrPageIndex -= 1;
                        mChange = true;
                        
                    } else if (((velocityX < -SNAP_VELOCITY) || (deltaX > mWidth / PAGE_FACTOR))
                            && mCurrPageIndex < (mPageCount - 1)) {
                        mCurrPageIndex += 1;
                        mChange = true;
                    }
                    mScrollView.smoothScrollTo(mCurrPageIndex * mWidth, 0);
                    if (mChange) {
                        if (mOnPageChangeListener != null) {
                            mOnPageChangeListener.onPageChange();
                        }
                        mChange = false;
                    }
                    if (mVelocityTracker != null) {
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }
                return true; // break;
                default:
                    break;
            }
            return false;
        }
    };

    /**
     * The listener interface for receiving onPageChange events.
     * The class that is interested in processing a onPageChange
     * event implements this interface, and the object created
     * with that class is registered with a component using the
     * component's <code>addonPageChangeListener<code> method. When
     * the onPageChange event occurs, that object's appropriate
     * method is invoked.
     *
     * @see onPageChangeEvent
     */
    public interface OnPageChangeListener {
        
        /**
         * On page change.
         */
        void onPageChange();
    }

    /** The m on page change listener. */
    private OnPageChangeListener mOnPageChangeListener;

    /**
     * Sets the on page change listener.
     *
     * @param l the new on page change listener
     */
    public void setOnPageChangeListener(OnPageChangeListener l) {
        mOnPageChangeListener = l;
    }
    
    /**
     * Sets the page index.
     *
     * @param index the new page index
     */
    public void setPageIndex(int index) {
        if (index < 0 || index > mPageCount - 1 || index == mCurrPageIndex) {
            return;
        }
        
        mCurrPageIndex = index;
        mScrollView.smoothScrollTo(mCurrPageIndex * mWidth, 0);
    }
}

评论

2 楼 康妮西 2011-06-09  

求这个View的解释

望博主联系，我的联系方式：

[e-mail] 或 QQ： 1047286578

1 楼 muyu114 2011-05-16  

你这个是啥意思啊，有什么效果没有