android -------- RecyclerView的可（多个Item水平，垂直）滚动列表的实现

RecyclerView的可滚动的列表实现,视图相邻的视图在屏幕上部分或完全可见(水平3个item，第一个和第三个显示一部分，第二个完全显示)

效果如图：

基于RecyclerView完成的（自定义控件）

public class DiscreteRecyclerView extends RecyclerView {    public static final int NO_POSITION = DiscreteRecyclerLayoutManager.NO_POSITION;    private static final int DEFAULT_ORIENTATION = DSVOrientation.HORIZONTAL.ordinal();    private DiscreteRecyclerLayoutManager layoutManager;    private List scrollStateChangeListeners;    private List onItemChangedListeners;    private boolean isOverScrollEnabled;    public DiscreteRecyclerView(Context context) {        super(context);        init(null);    }    public DiscreteRecyclerView(Context context, AttributeSet attrs) {        super(context, attrs);        init(attrs);    }    public DiscreteRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init(attrs);    }    private void init(AttributeSet attrs) {        scrollStateChangeListeners = new ArrayList<>();        onItemChangedListeners = new ArrayList<>();        int orientation = DEFAULT_ORIENTATION;        if (attrs != null) {            TypedArray ta = getContext().obtainStyledAttributes(attrs, R.styleable.DiscreteRecyclerView);            orientation = ta.getInt(R.styleable.DiscreteRecyclerView_dsv_orientation, DEFAULT_ORIENTATION);            ta.recycle();        }        isOverScrollEnabled = getOverScrollMode() != OVER_SCROLL_NEVER;        layoutManager = new DiscreteRecyclerLayoutManager(                getContext(), new ScrollStateListener(),                DSVOrientation.values()[orientation]);        setLayoutManager(layoutManager);    }    @Override    public void setLayoutManager(LayoutManager layout) {        if (layout instanceof DiscreteRecyclerLayoutManager) {            super.setLayoutManager(layout);        } else {            throw new IllegalArgumentException(getContext().getString(R.string.dsv_ex_msg_dont_set_lm));        }    }    @Override    public boolean fling(int velocityX, int velocityY) {        boolean isFling = super.fling(velocityX, velocityY);        if (isFling) {            layoutManager.onFling(velocityX, velocityY);        } else {            layoutManager.returnToCurrentPosition();        }        return isFling;    }    @Nullable    public ViewHolder getViewHolder(int position) {        View view = layoutManager.findViewByPosition(position);        return view != null ? getChildViewHolder(view) : null;    }    /**     * @return adapter position of the current item or -1 if nothing is selected     */    public int getCurrentItem() {        return layoutManager.getCurrentPosition();    }    public void setItemTransformer(DiscreteScrollItemTransformer transformer) {        layoutManager.setItemTransformer(transformer);    }    public void setItemTransitionTimeMillis(@IntRange(from = 10) int millis) {        layoutManager.setTimeForItemSettle(millis);    }    public void setSlideOnFling(boolean result){        layoutManager.setShouldSlideOnFling(result);    }    public void setSlideOnFlingThreshold(int threshold){        layoutManager.setSlideOnFlingThreshold(threshold);    }    public void setOrientation(DSVOrientation orientation) {        layoutManager.setOrientation(orientation);    }    public void setOffscreenItems(int items) {        layoutManager.setOffscreenItems(items);    }    public void setClampTransformProgressAfter(@IntRange(from = 1) int itemCount) {        if (itemCount <= 1) {            throw new IllegalArgumentException("must be >= 1");        }        layoutManager.setTransformClampItemCount(itemCount);    }    public void setOverScrollEnabled(boolean overScrollEnabled) {        isOverScrollEnabled = overScrollEnabled;        setOverScrollMode(OVER_SCROLL_NEVER);    }    public void addScrollStateChangeListener(@NonNull ScrollStateChangeListener<?> scrollStateChangeListener) {        scrollStateChangeListeners.add(scrollStateChangeListener);    }    public void addScrollListener(@NonNull ScrollListener<?> scrollListener) {        addScrollStateChangeListener(new ScrollListenerAdapter(scrollListener));    }    public void addOnItemChangedListener(@NonNull OnItemChangedListener<?> onItemChangedListener) {        onItemChangedListeners.add(onItemChangedListener);    }    public void removeScrollStateChangeListener(@NonNull ScrollStateChangeListener<?> scrollStateChangeListener) {        scrollStateChangeListeners.remove(scrollStateChangeListener);    }    public void removeScrollListener(@NonNull ScrollListener<?> scrollListener) {        removeScrollStateChangeListener(new ScrollListenerAdapter<>(scrollListener));    }    public void removeItemChangedListener(@NonNull OnItemChangedListener<?> onItemChangedListener) {        onItemChangedListeners.remove(onItemChangedListener);    }    private void notifyScrollStart(ViewHolder holder, int current) {        for (ScrollStateChangeListener listener : scrollStateChangeListeners) {            listener.onScrollStart(holder, current);        }    }    private void notifyScrollEnd(ViewHolder holder, int current) {        for (ScrollStateChangeListener listener : scrollStateChangeListeners) {            listener.onScrollEnd(holder, current);        }    }    private void notifyScroll(float position,                              int currentIndex, int newIndex,                              ViewHolder currentHolder, ViewHolder newHolder) {        for (ScrollStateChangeListener listener : scrollStateChangeListeners) {            listener.onScroll(position, currentIndex, newIndex,                currentHolder,                newHolder);        }    }    private void notifyCurrentItemChanged(ViewHolder holder, int current) {        for (OnItemChangedListener listener : onItemChangedListeners) {            listener.onCurrentItemChanged(holder, current);        }    }    private void notifyCurrentItemChanged() {        if (onItemChangedListeners.isEmpty()) {            return;        }        int current = layoutManager.getCurrentPosition();        ViewHolder currentHolder = getViewHolder(current);        notifyCurrentItemChanged(currentHolder, current);    }    private class ScrollStateListener implements DiscreteRecyclerLayoutManager.ScrollStateListener {        @Override        public void onIsBoundReachedFlagChange(boolean isBoundReached) {            if (isOverScrollEnabled) {                setOverScrollMode(isBoundReached ? OVER_SCROLL_ALWAYS : OVER_SCROLL_NEVER);            }        }        @Override        public void onScrollStart() {            if (scrollStateChangeListeners.isEmpty()) {                return;            }            int current = layoutManager.getCurrentPosition();            ViewHolder holder = getViewHolder(current);            if (holder != null) {                notifyScrollStart(holder, current);            }        }        @Override        public void onScrollEnd() {            if (onItemChangedListeners.isEmpty() && scrollStateChangeListeners.isEmpty()) {                return;            }            int current = layoutManager.getCurrentPosition();            ViewHolder holder = getViewHolder(current);            if (holder != null) {                notifyScrollEnd(holder, current);                notifyCurrentItemChanged(holder, current);            }        }        @Override        public void onScroll(float currentViewPosition) {            if (scrollStateChangeListeners.isEmpty()) {                return;            }            int currentIndex = getCurrentItem();            int newIndex = layoutManager.getNextPosition();            if (currentIndex != newIndex) {                notifyScroll(currentViewPosition,                    currentIndex, newIndex,                    getViewHolder(currentIndex),                    getViewHolder(newIndex));            }        }        @Override        public void onCurrentViewFirstLayout() {            post(new Runnable() {                @Override                public void run() {                    notifyCurrentItemChanged();                }            });        }        @Override        public void onDataSetChangeChangedPosition() {            notifyCurrentItemChanged();        }    }    public interface ScrollStateChangeListener {        void onScrollStart(@NonNull T currentItemHolder, int adapterPosition);        void onScrollEnd(@NonNull T currentItemHolder, int adapterPosition);        void onScroll(float scrollPosition,                      int currentPosition,                      int newPosition,                      @Nullable T currentHolder,                      @Nullable T newCurrent);    }    public interface ScrollListener {        void onScroll(float scrollPosition,                      int currentPosition, int newPosition,                      @Nullable T currentHolder,                      @Nullable T newCurrent);    }    public interface OnItemChangedListener {        /*         * This method will be also triggered when view appears on the screen for the first time.         * If data set is empty, viewHolder will be null and adapterPosition will be NO_POSITION         */        void onCurrentItemChanged(@Nullable T viewHolder, int adapterPosition);    }}

源码：https://github.com/DickyQie/android-discrete-recyclerview

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