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<ScrollStateChangeListener> scrollStateChangeListeners;
private List<OnItemChangedListener> 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<T extends ViewHolder> {
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<T extends ViewHolder> {
void onScroll(float scrollPosition,
int currentPosition, int newPosition,
@Nullable T currentHolder,
@Nullable T newCurrent);
}
public interface OnItemChangedListener<T extends ViewHolder> {
/*
* 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