Java Code Examples for androidx.recyclerview.widget.LinearLayoutManager#scrollToPositionWithOffset()

private void setUpRecyclerView() {
    recyclerViewDragDropManager = new RecyclerViewDragDropManager();
    final GeneralItemAnimator animator = new RefactoredDefaultItemAnimator();

    playingQueueAdapter = new PlayingQueueAdapter(
            ((AppCompatActivity) getActivity()),
            MusicPlayerRemote.getPlayingQueue(),
            MusicPlayerRemote.getPosition(),
            R.layout.item_list,
            false,
            null);
    wrappedAdapter = recyclerViewDragDropManager.createWrappedAdapter(playingQueueAdapter);

    layoutManager = new LinearLayoutManager(getActivity());

    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setAdapter(wrappedAdapter);
    recyclerView.setItemAnimator(animator);

    recyclerViewDragDropManager.attachRecyclerView(recyclerView);

    layoutManager.scrollToPositionWithOffset(MusicPlayerRemote.getPosition() + 1, 0);
}
 

public void handleCommentVisibilityToggle(final RedditCommentView view) {

		final RedditChangeDataManager changeDataManager = RedditChangeDataManager.getInstance(mUser);
		final RedditCommentListItem item = view.getComment();

		if(item.isComment()) {
			final RedditRenderableComment comment = item.asComment();

			changeDataManager.markHidden(
					RRTime.utcCurrentTimeMillis(),
					comment,
					!comment.isCollapsed(changeDataManager));

			mCommentListingManager.updateHiddenStatus();

			final LinearLayoutManager layoutManager = (LinearLayoutManager)mRecyclerView.getLayoutManager();
			final int position = layoutManager.getPosition(view);

			if(position == layoutManager.findFirstVisibleItemPosition()) {
				layoutManager.scrollToPositionWithOffset(position, 0);
			}
		}
	}
 

public void onPostsAdded() {

		if(mPreviousFirstVisibleItemPosition == null) {
			return;
		}

		final LinearLayoutManager layoutManager = (LinearLayoutManager)mRecyclerView.getLayoutManager();

		if(layoutManager.getItemCount() > mPreviousFirstVisibleItemPosition) {
			layoutManager.scrollToPositionWithOffset(mPreviousFirstVisibleItemPosition, 0);
			mPreviousFirstVisibleItemPosition = null;

		} else {
			layoutManager.scrollToPosition(layoutManager.getItemCount() - 1);
		}
	}
 

@Override
void scrollToPosition(RecyclerView list, int pos) {
    if (list.getLayoutManager() instanceof LinearLayoutManager) {
        // Centering item in its parent
        final LinearLayoutManager manager = (LinearLayoutManager) list.getLayoutManager();
        final boolean isHorizontal = manager.getOrientation() == LinearLayoutManager.HORIZONTAL;

        int offset = isHorizontal
                ? (list.getWidth() - list.getPaddingLeft() - list.getPaddingRight()) / 2
                : (list.getHeight() - list.getPaddingTop() - list.getPaddingBottom()) / 2;

        final RecyclerView.ViewHolder holder = list.findViewHolderForAdapterPosition(pos);
        if (holder != null) {
            final View view = holder.itemView;
            offset -= isHorizontal ? view.getWidth() / 2 : view.getHeight() / 2;
        }

        manager.scrollToPositionWithOffset(pos, offset);
    } else {
        list.scrollToPosition(pos);
    }
}
 

private void setUpRecyclerView() {
    recyclerViewDragDropManager = new RecyclerViewDragDropManager();
    final GeneralItemAnimator animator = new RefactoredDefaultItemAnimator();

    playingQueueAdapter = new PlayingQueueAdapter(
            ((AppCompatActivity) getActivity()),
            MusicPlayerRemote.getPlayingQueue(),
            MusicPlayerRemote.getPosition(),
            R.layout.item_list,
            false,
            null);
    wrappedAdapter = recyclerViewDragDropManager.createWrappedAdapter(playingQueueAdapter);

    layoutManager = new LinearLayoutManager(getActivity());

    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setAdapter(wrappedAdapter);
    recyclerView.setItemAnimator(animator);

    recyclerViewDragDropManager.attachRecyclerView(recyclerView);

    layoutManager.scrollToPositionWithOffset(MusicPlayerRemote.getPosition() + 1, 0);
}
 

private void setUpRecyclerView() {
    recyclerViewDragDropManager = new RecyclerViewDragDropManager();
    final GeneralItemAnimator animator = new RefactoredDefaultItemAnimator();

    playingQueueAdapter = new PlayingQueueAdapter(
            ((AppCompatActivity) getActivity()),
            MusicPlayerRemote.getPlayingQueue(),
            MusicPlayerRemote.getPosition(),
            R.layout.item_list,
            false,
            null);
    wrappedAdapter = recyclerViewDragDropManager.createWrappedAdapter(playingQueueAdapter);

    layoutManager = new LinearLayoutManager(getActivity());

    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setAdapter(wrappedAdapter);
    recyclerView.setItemAnimator(animator);

    recyclerViewDragDropManager.attachRecyclerView(recyclerView);

    layoutManager.scrollToPositionWithOffset(MusicPlayerRemote.getPosition() + 1, 0);
}
 

/**
 * Scrolls a view at the given position to top (vertical layout) or left (horizontal layout).
 *
 * @param position The adapter position.
 */
public void head(int position) {
    if (mIgnoreIfCompletelyVisible && isCompletelyVisible(position)) {
        return;
    }

    if (mIgnoreIfVisible && isVisible(position)) {
        return;
    }

    LayoutManager lm = getLayoutManager();
    if (lm instanceof LinearLayoutManager) {
        LinearLayoutManager llm = (LinearLayoutManager) lm;
        llm.scrollToPositionWithOffset(position, 0);
    } else if (lm instanceof StaggeredGridLayoutManager) {
        final StaggeredGridLayoutManager sglm = (StaggeredGridLayoutManager) lm;
        sglm.scrollToPositionWithOffset(position, 0);
    } else {
        throw new UnsupportedOperationException("unsupported layout manager");
    }
}
 

private void scrollToCurrent() {
    if (getDownloadService() == null || songListAdapter == null) {
        scrollWhenLoaded = true;
        return;
    }

    // Try to get position of current playing/downloading
    int position = songListAdapter.getItemPosition(currentPlaying);
    if (position == -1) {
        DownloadFile currentDownloading = getDownloadService().getCurrentDownloading();
        position = songListAdapter.getItemPosition(currentDownloading);
    }

    // If found, scroll to it
    if (position != -1) {
        // RecyclerView.scrollToPosition just puts it on the screen (ie: bottom if scrolled below it)
        LinearLayoutManager layoutManager = (LinearLayoutManager) playlistView.getLayoutManager();
        layoutManager.scrollToPositionWithOffset(position, 0);
    }
}
 

@Override
public void onLetterChange(String letter) {
    if (mRecyclerView.getAdapter() == null){
        return;
    }
    ItemArray itemArray = ((AppAdapter) mRecyclerView.getAdapter()).getItems();
    int size = itemArray.size();
    for (int i = 0; i < size; i++) {
        ItemData data = itemArray.get(i);
        if (data.getDataType() == AppAdapter.TYPE_STICKY) {
            App app = data.getData();
            if (app.namePinyin.startsWith(letter)) {
                LinearLayoutManager mLayoutManager =
                        (LinearLayoutManager) mRecyclerView.getLayoutManager();
                mLayoutManager.scrollToPositionWithOffset(i, 0);
                return;
            }
        }
    }
}
 

private void setUpRecyclerView() {
    recyclerViewDragDropManager = new RecyclerViewDragDropManager();
    final GeneralItemAnimator animator = new RefactoredDefaultItemAnimator();

    playingQueueAdapter = new PlayingQueueAdapter(
            ((AppCompatActivity) getActivity()),
            MusicPlayerRemote.getPlayingQueue(),
            MusicPlayerRemote.getPosition(),
            R.layout.item_list,
            false,
            null);
    wrappedAdapter = recyclerViewDragDropManager.createWrappedAdapter(playingQueueAdapter);

    layoutManager = new LinearLayoutManager(getActivity());

    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setAdapter(wrappedAdapter);
    recyclerView.setItemAnimator(animator);

    recyclerViewDragDropManager.attachRecyclerView(recyclerView);

    layoutManager.scrollToPositionWithOffset(MusicPlayerRemote.getPosition() + 1, 0);
}
 

public void move(int n) {
    if (n < 0 || n >= getAdapter().getItemCount()) {
        PtrCLog.e(TAG, "move: index error");
        return;
    }
    mRecyclerView.stopScroll();
    LinearLayoutManager linearLayoutManager = (LinearLayoutManager) getRecyclerView().getLayoutManager();
    linearLayoutManager.scrollToPositionWithOffset(n, 0);
}
 

/**
 * Scrolls to the specified fraction of the RV
 *
 * @param touchFraction the fraction of the RV to scroll through
 * @return the distance traveled by the RV in the transformation applied by this method.
 * + is downward, - upward.
 */
int scrollToPositionAtProgress(float touchFraction) {
    int priorPosition = materialScrollBar.recyclerView.computeVerticalScrollOffset();
    int exactItemPos;
    if(customScroller == null) {
        int spanCount = 1;
        if(materialScrollBar.recyclerView.getLayoutManager() instanceof GridLayoutManager) {
            spanCount = ((GridLayoutManager) materialScrollBar.recyclerView.getLayoutManager()).getSpanCount();
        }

        // Stop the scroller if it is scrolling
        materialScrollBar.recyclerView.stopScroll();

        getCurScrollState();

        //The exact position of our desired item
        exactItemPos = (int) (getAvailableScrollHeight() * touchFraction);

        //Scroll to the desired item. The offset used here is kind of hard to explain.
        //If the position we wish to scroll to is, say, position 10.5, we scroll to position 10,
        //and then offset by 0.5 * rowHeight. This is how we achieve smooth scrolling.
        LinearLayoutManager layoutManager = ((LinearLayoutManager) materialScrollBar.recyclerView.getLayoutManager());
        try {
            layoutManager.scrollToPositionWithOffset(spanCount * exactItemPos / scrollPosState.rowHeight,
                    -(exactItemPos % scrollPosState.rowHeight));
        } catch (ArithmeticException e) { /* Avoids issues where children of RV have not yet been laid out */ }
    } else {
        if(layoutManager == null) {
            layoutManager = ((LinearLayoutManager) materialScrollBar.recyclerView.getLayoutManager());
        }
        exactItemPos = customScroller.getItemIndexForScroll(touchFraction);
        int offset = (int) (customScroller.getDepthForItem(exactItemPos) - touchFraction * getAvailableScrollHeight());
        layoutManager.scrollToPositionWithOffset(exactItemPos, offset);
        return 0;
    }
    return exactItemPos - priorPosition;
}
 

public void scroll(boolean up) {
    ArticleListFragment currentFragment = getCurrentFragment();

    if (currentFragment != null && currentFragment.recyclerViewLayoutManager != null) {
        LinearLayoutManager listLayout = currentFragment.recyclerViewLayoutManager;

        int numberOfVisibleItems =
                listLayout.findLastCompletelyVisibleItemPosition() -
                        listLayout.findFirstCompletelyVisibleItemPosition() + 1;

        int oldPositionOnTop = listLayout.findFirstCompletelyVisibleItemPosition();

        // scroll so that as many new articles are visible than possible with one overlap
        int newPositionOnTop;
        if (up) {
            newPositionOnTop = oldPositionOnTop - numberOfVisibleItems + 1;
        } else {
            newPositionOnTop = oldPositionOnTop + numberOfVisibleItems - 1;
        }

        if (newPositionOnTop >= listLayout.getItemCount()) {
            newPositionOnTop = listLayout.getItemCount() - numberOfVisibleItems - 1;
        } else if (newPositionOnTop < 0) {
            newPositionOnTop = 0;
        }

        Log.v(TAG, " scrolling to position: " + newPositionOnTop);

        listLayout.scrollToPositionWithOffset(newPositionOnTop, 0);
    }
}
 

private void scrollToPositionWithOffset(int position, int offset) {
    LinearLayoutManager linearLayoutManager = getVerticalLinearLayoutManager();
    if (linearLayoutManager == null) {
        return;
    }
    if (linearLayoutManager instanceof GridLayoutManager) {
        GridLayoutManager gridLayoutManager = (GridLayoutManager) linearLayoutManager;
        position *= gridLayoutManager.getSpanCount();
    }
    // LinearLayoutManager actually takes offset from paddingTop instead of top of RecyclerView.
    offset -= mView.getPaddingTop();
    linearLayoutManager.scrollToPositionWithOffset(position, offset);
}
 

/**
 * 滚动到底部（不带动画）
 */
private void scrollToBottom() {
    LinearLayoutManager ll = (LinearLayoutManager) mRecyclerView.getLayoutManager();
    ll.scrollToPositionWithOffset(getBottomDataPosition(), 0);
}
 

private void setRecyclerViewPosition(float y) {
    if (recyclerView != null) {
        if (recyclerView.getChildCount() == 0) {
            return;
        }

        int itemCount = recyclerView.getAdapter().getItemCount();
        float proportion = getValueInRange(1f, y / (float) height);

        float targetPosFloat = getValueInRange(itemCount - 1, proportion * (float) itemCount);
        int targetPos = (int) targetPosFloat;

        // Immediately make sure that the target is visible
        LinearLayoutManager layoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
        // layoutManager.scrollToPositionWithOffset(targetPos, 0);
        View firstVisibleView = recyclerView.getChildAt(0);

        // Calculate how far through this position we are
        int columns = Math.round(recyclerView.getWidth() / firstVisibleView.getWidth());
        int firstVisiblePosition = recyclerView.getChildAdapterPosition(firstVisibleView);
        int remainder = (targetPos - firstVisiblePosition) % columns;
        float offsetPercentage = (targetPosFloat - targetPos + remainder) / columns;
        if (offsetPercentage < 0) {
            offsetPercentage = 1 + offsetPercentage;
        }
        int firstVisibleHeight = firstVisibleView.getHeight();
        if (columns > 1) {
            firstVisibleHeight += (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, GridSpacingDecoration.SPACING, firstVisibleView.getResources().getDisplayMetrics());
        }
        int offset = (int) (offsetPercentage * firstVisibleHeight);

        layoutManager.scrollToPositionWithOffset(targetPos, -offset);
        onUpdateScroll(1, 1);

        try {
            String bubbleText = null;
            RecyclerView.Adapter adapter = recyclerView.getAdapter();
            if (adapter instanceof BubbleTextGetter) {
                bubbleText = ((BubbleTextGetter) adapter).getTextToShowInBubble(targetPos);
            }

            if (bubbleText == null) {
                visibleBubble = false;
                bubble.setVisibility(View.INVISIBLE);
            } else {
                bubble.setText(bubbleText);
                bubble.setVisibility(View.VISIBLE);
                visibleBubble = true;
            }
        } catch (Exception e) {
            Log.e(TAG, "Error getting text for bubble", e);
        }
    }
}
 

/**
 * Maps the touch (from 0..1) to the adapter position that should be visible.
 */
public String scrollToPositionAtProgress(float touchFraction) {
    int itemCount = getAdapter().getItemCount();
    if (itemCount == 0) {
        return "";
    }
    int spanCount = 1;
    int rowCount = itemCount;
    if (getLayoutManager() instanceof GridLayoutManager) {
        spanCount = ((GridLayoutManager) getLayoutManager()).getSpanCount();
        rowCount = (int) Math.ceil((double) rowCount / spanCount);
    }

    // Stop the scroller if it is scrolling
    stopScroll();

    getCurScrollState(mScrollPosState);

    float itemPos = itemCount * touchFraction;

    int availableScrollHeight = getAvailableScrollHeight(rowCount, mScrollPosState.rowHeight, 0);

    //The exact position of our desired item
    int exactItemPos = (int) (availableScrollHeight * touchFraction);

    //Scroll to the desired item. The offset used here is kind of hard to explain.
    //If the position we wish to scroll to is, say, position 10.5, we scroll to position 10,
    //and then offset by 0.5 * rowHeight. This is how we achieve smooth scrolling.
    LinearLayoutManager layoutManager = ((LinearLayoutManager) getLayoutManager());
    layoutManager.scrollToPositionWithOffset(spanCount * exactItemPos / mScrollPosState.rowHeight,
            -(exactItemPos % mScrollPosState.rowHeight));

    if (!(getAdapter() instanceof SectionedAdapter)) {
        return "";
    }

    int posInt = (int) ((touchFraction == 1) ? itemPos - 1 : itemPos);

    SectionedAdapter sectionedAdapter = (SectionedAdapter) getAdapter();
    return sectionedAdapter.getSectionName(posInt);
}
 

private void setScrollPosition(ScrollState scrollPosition) {
    if (scrollPosition != null) {
        LinearLayoutManager layoutManager = (LinearLayoutManager) binding.list.getLayoutManager();
        layoutManager.scrollToPositionWithOffset(scrollPosition.position, scrollPosition.offset);
    }
}
 

@Override
public void onCommentListingRequestAllItemsDownloaded(final ArrayList<RedditCommentListItem> items) {

	mCommentListingManager.addComments(items);

	if(mFloatingToolbar != null && mFloatingToolbar.getVisibility() != View.VISIBLE) {
		mFloatingToolbar.setVisibility(View.VISIBLE);
		final Animation animation = AnimationUtils.loadAnimation(getContext(), R.anim.slide_in_from_bottom);
		animation.setInterpolator(new OvershootInterpolator());
		mFloatingToolbar.startAnimation(animation);
	}

	mUrlsToDownload.removeFirst();

	final LinearLayoutManager layoutManager = (LinearLayoutManager)mRecyclerView.getLayoutManager();

	if(mPreviousFirstVisibleItemPosition != null
			&& layoutManager.getItemCount() > mPreviousFirstVisibleItemPosition) {

		layoutManager.scrollToPositionWithOffset(
				mPreviousFirstVisibleItemPosition,
				0);

		mPreviousFirstVisibleItemPosition = null;
	}

	if(mUrlsToDownload.isEmpty()) {

		if(mCommentListingManager.getCommentCount() == 0) {

			final View emptyView = LayoutInflater.from(getContext()).inflate(
					R.layout.no_comments_yet,
					mRecyclerView,
					false);

			if (mCommentListingManager.isSearchListing()) {
				((TextView) emptyView.findViewById(R.id.empty_view_text)).setText(R.string.no_search_results);
			}

			mCommentListingManager.addViewToItems(emptyView);

		} else {

			final View blankView = new View(getContext());
			blankView.setMinimumWidth(1);
			blankView.setMinimumHeight(General.dpToPixels(getContext(), 96));
			mCommentListingManager.addViewToItems(blankView);
		}

		mCommentListingManager.setLoadingVisible(false);

	} else {
		makeNextRequest(getActivity());
	}
}