Android 横向ListView

横向ListView:

/**
 * 自定义的一个水平方向的ListView，用法和ListView一样，也是去设置适配器(BaseAdapter的子类)
 */
public class HorizontialListView 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 boolean mDataChanged = false;
    public HorizontialListView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initView();
    }
    public HorizontialListView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initView();
    }
    public HorizontialListView(Context context) {
        super(context);
        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;
    }
    private DataSetObserver mDataObserver = new DataSetObserver() {
        @Override
        public void onChanged() {
            synchronized (HorizontialListView.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();
            }
            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;
            }
        }
    }
    public synchronized void scrollTo(int x) {
        mScroller.startScroll(mNextX, 0, x - mNextX, 0);
        requestLayout();
    }
    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        boolean handled = mGesture.onTouchEvent(ev);
        return handled;
    }
    protected boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
            float velocityY) {
        synchronized (HorizontialListView.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 HorizontialListView.this.onDown(e);
        }
        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY) {
            return HorizontialListView.this.onFling(e1, e2, velocityX,
                    velocityY);
        }
        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2,
                float distanceX, float distanceY) {
            synchronized (HorizontialListView.this) {
                mNextX += (int) distanceX;
            }
            requestLayout();
            return true;
        }
        @Override
        public boolean onSingleTapConfirmed(MotionEvent e) {
            Rect viewRect = new Rect();
            for (int i = 0; i < getChildCount(); i++) {
                View child = getChildAt(i);
                int left = child.getLeft();
                int right = child.getRight();
                int top = child.getTop();
                int bottom = child.getBottom();
                viewRect.set(left, top, right, bottom);
                if (viewRect.contains((int) e.getX(), (int) e.getY())) {
                    if (mOnItemClicked != null) {
                        mOnItemClicked.onItemClick(HorizontialListView.this,
                                child, mLeftViewIndex + 1 + i,
                                mAdapter.getItemId(mLeftViewIndex + 1 + i));
                    }
                    if (mOnItemSelected != null) {
                        mOnItemSelected.onItemSelected(
                                HorizontialListView.this, child, mLeftViewIndex
                                        + 1 + i,
                                mAdapter.getItemId(mLeftViewIndex + 1 + i));
                    }
                    break;
                }
            }
            return true;
        }
    };
}