Android中实现水平滑动（横向滑动）ListView示例

水平的ListView-HorizontalListView的使用

Android中ListView默认的是竖直方向的滑动，由于项目的需求，需要ListView是水平滑动的。有很多的方式可以实现，但是比较好的一种方式就是自己封装一个控件，使用方式和ListView的使用方式是一样的。需要完善的地方：获取到的图片大小没有处理。在界面上展示的是图片的原大小。为了更好的展示效果，应该压缩成统一的尺寸。

HorizontalListView.java 代码如下：

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

  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<View> mRemovedViewQueue = new LinkedList<View>();
  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 < getWidth()
        && mRightViewIndex < mAdapter.getCount()) {

      View child = mAdapter.getView(mRightViewIndex,
          mRemovedViewQueue.poll(), this);
      addAndMeasureChild(child, -1);
      rightEdge += child.getMeasuredWidth();

      if (mRightViewIndex == mAdapter.getCount() - 1) {
        mMaxX = mCurrentX + rightEdge - getWidth();
      }

      if (mMaxX < 0) {
        mMaxX = 0;
      }
      mRightViewIndex++;
    }

  }

  private void fillListLeft(int leftEdge, final int dx) {
    while (leftEdge + 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 < getChildCount(); i++) {
        View child = getChildAt(i);
        int childWidth = child.getMeasuredWidth();
        child.layout(left, 0, left + childWidth,
            child.getMeasuredHeight());
        left += childWidth + child.getPaddingRight();
      }
    }
  }

  public synchronized void scrollTo(int x) {
    mScroller.startScroll(mNextX, 0, x - mNextX, 0);
    requestLayout();
  }

  @Override
  public boolean dispatchTouchEvent(MotionEvent ev) {
    boolean handled = super.dispatchTouchEvent(ev);
    handled |= mGesture.onTouchEvent(ev);
    return handled;
  }

  protected boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
      float velocityY) {
    synchronized (HorizontalListView.this) {
      mScroller.fling(mNextX, 0, (int) -velocityX, 0, 0, mMaxX, 0, 0);
    }
    requestLayout();

    return true;
  }

  protected boolean onDown(MotionEvent e) {
    mScroller.forceFinished(true);
    return true;
  }

  private OnGestureListener mOnGesture = new GestureDetector.SimpleOnGestureListener() {

    @Override
    public boolean onDown(MotionEvent e) {
      return HorizontalListView.this.onDown(e);
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
        float velocityY) {
      return HorizontalListView.this
          .onFling(e1, e2, velocityX, velocityY);
    }

    @Override
    public boolean onScroll(MotionEvent e1, MotionEvent e2,
        float distanceX, float distanceY) {

      synchronized (HorizontalListView.this) {
        mNextX += (int) distanceX;
      }
      requestLayout();

      return true;
    }

    @Override
    public boolean onSingleTapConfirmed(MotionEvent e) {
      for (int i = 0; i < getChildCount(); i++) {
        View child = getChildAt(i);
        if (isEventWithinView(e, child)) {
          if (mOnItemClicked != null) {
            mOnItemClicked.onItemClick(HorizontalListView.this,
                child, mLeftViewIndex + 1 + i,
                mAdapter.getItemId(mLeftViewIndex + 1 + i));
          }
          if (mOnItemSelected != null) {
            mOnItemSelected.onItemSelected(HorizontalListView.this,
                child, mLeftViewIndex + 1 + i,
                mAdapter.getItemId(mLeftViewIndex + 1 + i));
          }
          break;
        }

      }
      return true;
    }

    @Override
    public void onLongPress(MotionEvent e) {
      int childCount = getChildCount();
      for (int i = 0; i < childCount; i++) {
        View child = getChildAt(i);
        if (isEventWithinView(e, child)) {
          if (mOnItemLongClicked != null) {
            mOnItemLongClicked.onItemLongClick(
                HorizontalListView.this, child, mLeftViewIndex
                    + 1 + i,
                mAdapter.getItemId(mLeftViewIndex + 1 + i));
          }
          break;
        }
      }
    }

    private boolean isEventWithinView(MotionEvent e, View child) {
      Rect viewRect = new Rect();
      int[] childPosition = new int[2];
      child.getLocationOnScreen(childPosition);
      int left = childPosition[0];
      int right = left + child.getWidth();
      int top = childPosition[1];
      int bottom = top + child.getHeight();
      viewRect.set(left, top, right, bottom);
      return viewRect.contains((int) e.getRawX(), (int) e.getRawY());
    }
  };

}

适配器 HorizontalListViewAdapter .java如下：

public class HorizontalListViewAdapter extends BaseAdapter {
  /** 上下文 */
  private Context mContext;
  /** 图像数据源 */
  private ArrayList<Map<String, Integer>> mImageList;

  /** 数据源 */
  private ArrayList<Map<String, Integer>> mTextList;
  /** Image */
  private static String IMAGE = "ic_";

  private Map<String, Integer> mMap = null;

  /** 构造方法 */
  public HorizontalListViewAdapter(Context context) {
    this.mContext = context;
    initData();
  }

  /** 初始化数据 */
  public void initData() {
    mImageList = new ArrayList<Map<String, Integer>>();
    /*
     * 反射技术
     */
    Class<?> imageClzz = R.drawable.class;
    R.drawable instance = new R.drawable();
    // 取得drawable类中所有的字段
    Field[] fields = imageClzz.getDeclaredFields();
    for (Field field : fields) {
      // 获得字段的名字
      String name = field.getName();
      if (name != null && name.startsWith(IMAGE)) {
        try {
          mMap = new HashMap<String, Integer>();
          mMap.put(IMAGE, (Integer) field.get(instance));
          mImageList.add(mMap);
        } catch (IllegalAccessException e) {
          e.printStackTrace();
        }
      }

    }
  }

  @Override
  public int getCount() {
    return mImageList.size();
  }

  @Override
  public Map<String, Integer> getItem(int position) {

    return mImageList == null ? null : mImageList.get(position);
  }

  @Override
  public long getItemId(int position) {
    return position;
  }

  @Override
  public View getView(int position, View convertView, ViewGroup parent) {

    ViewHolder holder;
    if (convertView == null) {
      holder = new ViewHolder();
      convertView = LayoutInflater.from(mContext).inflate(
          R.layout.horizontal_list_item, null);
      holder.mImage = (ImageView) convertView
          .findViewById(R.id.iv_list_item);
      holder.mTitle = (TextView) convertView
          .findViewById(R.id.tv_list_item);
      convertView.setTag(holder);
    } else {
      holder = (ViewHolder) convertView.getTag();
    }

    if (position == mSelectIndex) {
      convertView.setSelected(true);
    } else {
      convertView.setSelected(false);
    }
    holder.mImage.setImageResource(getItem(position).get(IMAGE));
    return convertView;
  }

  private class ViewHolder {
    /** 图像 */
    private ImageView mImage;
  }
}