Android中实现水平滑动（横向滑动）ListView示例

/**
 * 横向的ListView
 * 
 * * @author scd
 * 
 */
public class HorizontalListView extends AdapterView {

  public boolean mAlwaysOverrideTouch = true;
  protected ListAdapter mAdapter;
  private int mLeftViewIndex = -1;
  private int mRightViewIndex = 0;
  protected int mCurrentX;
  protected int mNextX;
  private int mMaxX = Integer.MAX_VALUE;
  private int mDisplayOffset = 0;
  protected Scroller mScroller;
  private GestureDetector mGesture;
  private Queue mRemovedViewQueue = new LinkedList();
  private OnItemSelectedListener mOnItemSelected;
  private OnItemClickListener mOnItemClicked;
  private OnItemLongClickListener mOnItemLongClicked;
  private boolean mDataChanged = false;

  public HorizontalListView(Context context, AttributeSet attrs) {
    super(context, attrs);
    initView();
  }

  private synchronized void initView() {
    mLeftViewIndex = -1;
    mRightViewIndex = 0;
    mDisplayOffset = 0;
    mCurrentX = 0;
    mNextX = 0;
    mMaxX = Integer.MAX_VALUE;
    mScroller = new Scroller(getContext());
    mGesture = new GestureDetector(getContext(), mOnGesture);
  }

  @Override
  public void setOnItemSelectedListener(
      AdapterView.OnItemSelectedListener listener) {
    mOnItemSelected= listener;
  }

  @Override
  public void setOnItemClickListener(AdapterView.OnItemClickListener listener) {
    mOnItemClicked= listener;
  }

  @Override
  public void setOnItemLongClickListener(
      AdapterView.OnItemLongClickListener listener) {
    mOnItemLongClicked= listener;
  }

  private DataSetObserver mDataObserver = new DataSetObserver() {

    @Override
    public void onChanged() {
      synchronized (HorizontalListView.this) {
        mDataChanged = true;
      }
      invalidate();
      requestLayout();
    }

    @Override
    public void onInvalidated() {
      reset();
      invalidate();
      requestLayout();
    }

  };

  @Override
  public ListAdapter getAdapter() {
    return mAdapter;
  }

  @Override
  public View getSelectedView() {
    // TODO: implement
    return null;
  }

  @Override
  public void setAdapter(ListAdapter adapter) {
    if (mAdapter != null) {
      mAdapter.unregisterDataSetObserver(mDataObserver);
    }
    mAdapter = adapter;
    mAdapter.registerDataSetObserver(mDataObserver);
    reset();
  }

  private synchronized void reset() {
    initView();
    removeAllViewsInLayout();
    requestLayout();
  }

  @Override
  public void setSelection(int position) {
    // TODO: implement
  }

  private void addAndMeasureChild(final View child, int viewPos) {
    LayoutParams params = child.getLayoutParams();
    if (params == null) {
      params = new LayoutParams(LayoutParams.FILL_PARENT,
          LayoutParams.FILL_PARENT);
    }

    addViewInLayout(child, viewPos, params, true);
    child.measure(
        MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.AT_MOST),
        MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.AT_MOST));
  }

  @Override
  protected synchronized void onLayout(boolean changed, int left, int top,
      int right, int bottom) {
    super.onLayout(changed, left, top, right, bottom);

    if (mAdapter == null) {
      return;
    }

    if (mDataChanged) {
      int oldCurrentX = mCurrentX;
      initView();
      removeAllViewsInLayout();
      mNextX = oldCurrentX;
      mDataChanged = false;
    }

    if (mScroller.computeScrollOffset()) {
      int scrollx = mScroller.getCurrX();
      mNextX = scrollx;
    }

    if (mNextX <= 0) {
      mNextX = 0;
      mScroller.forceFinished(true);
    }
    if (mNextX >= mMaxX) {
      mNextX = mMaxX;
      mScroller.forceFinished(true);
    }

    int dx = mCurrentX - mNextX;

    removeNonVisibleItems(dx);
    fillList(dx);
    positionItems(dx);

    mCurrentX = mNextX;

    if (!mScroller.isFinished()) {
      post(new Runnable() {
        @Override
        public void run() {
          requestLayout();
        }
      });

    }
  }

  private void fillList(final int dx) {
    int edge = 0;
    View child = getChildAt(getChildCount() - 1);
    if (child != null) {
      edge = child.getRight();
    }
    fillListRight(edge, dx);

    edge = 0;
    child = getChildAt(0);
    if (child != null) {
      edge = child.getLeft();
    }
    fillListLeft(edge, dx);

  }

  private void fillListRight(int rightEdge, final int dx) {
    while (rightEdge + dx  0 && mLeftViewIndex >= 0) {
      View child = mAdapter.getView(mLeftViewIndex,
          mRemovedViewQueue.poll(), this);
      addAndMeasureChild(child, 0);
      leftEdge -= child.getMeasuredWidth();
      mLeftViewIndex--;
      mDisplayOffset -= child.getMeasuredWidth();
    }
  }

  private void removeNonVisibleItems(final int dx) {
    View child = getChildAt(0);
    while (child != null && child.getRight() + dx <= 0) {
      mDisplayOffset += child.getMeasuredWidth();
      mRemovedViewQueue.offer(child);
      removeViewInLayout(child);
      mLeftViewIndex++;
      child = getChildAt(0);

    }

    child = getChildAt(getChildCount() - 1);
    while (child != null && child.getLeft() + dx >= getWidth()) {
      mRemovedViewQueue.offer(child);
      removeViewInLayout(child);
      mRightViewIndex--;
      child = getChildAt(getChildCount() - 1);
    }
  }

  private void positionItems(final int dx) {
    if (getChildCount() > 0) {
      mDisplayOffset += dx;
      int left = mDisplayOffset;
      for (int i = 0; i