Java Code Examples for android.support.v7.widget.LinearLayoutManager#scrollToPositionWithOffset()

public static void scrollTo(Object scroll, float yOffset) {
    if (scroll instanceof RecyclerView) {
        //RecyclerView.scrollTo : UnsupportedOperationException
        //Moved to the RecyclerView.LayoutManager.scrollToPositionWithOffset
        //Have to be instanceOf RecyclerView.LayoutManager to work (so work with RecyclerView.GridLayoutManager)
        final RecyclerView.LayoutManager layoutManager = ((RecyclerView) scroll).getLayoutManager();
        if (layoutManager instanceof LinearLayoutManager) {
            LinearLayoutManager linearLayoutManager = (LinearLayoutManager) layoutManager;
            linearLayoutManager.scrollToPositionWithOffset(0, (int) -yOffset);
        } else if (layoutManager instanceof StaggeredGridLayoutManager) {
            StaggeredGridLayoutManager staggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
            staggeredGridLayoutManager.scrollToPositionWithOffset(0, (int) -yOffset);
        }
    } else if (scroll instanceof NestedScrollView) {
        ((NestedScrollView) scroll).scrollTo(0, (int) yOffset);
    }
}
 

static void fastScrollVertical(int amountAxis, RecyclerView recyclerView) {
    LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
    if (indexHeight == null) {
        indexHeight = new TreeMap<>();
        //call this method the OnScrollListener's onScrolled will be called，but dx and dy always be zero.
        linearLayoutManager.scrollToPositionWithOffset(0, -amountAxis);
    } else {
        int total = 0, count = 0;
        Iterator<Integer> iterator = indexHeight.keySet().iterator();
        while (null != iterator && iterator.hasNext()) {
            int height = indexHeight.get(iterator.next());
            if (total + height >= amountAxis) {
                break;
            }
            total += height;
            count++;
        }
        linearLayoutManager.scrollToPositionWithOffset(count, -(amountAxis - total));
    }
}
 

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);
}
 

@TargetApi(Build.VERSION_CODES.LOLLIPOP)
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 ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View layoutView = LayoutInflater.from(parent.getContext()).inflate(mLayoutId, parent, false);

    //create Recycler here
    MyRecyclerView recyclerView = (MyRecyclerView) layoutView.findViewById(R.id.horizontal_recycler_view);
    recyclerView.reboot(); //in case it's recycled

    // Create the right adapter for the recycler view
    HorizontalAdapter horizontalAdapter;
    horizontalAdapter = new HorizontalAdapter(recyclerView.getContext(), "", mTabNumber, mDarkTheme);

    // Set up the manager and adapter of the recycler view
    LinearLayoutManager horizontalLayoutManager = new LinearLayoutManager(mContext, LinearLayoutManager.HORIZONTAL, false);
    horizontalLayoutManager.scrollToPositionWithOffset(1, 0);
    recyclerView.setTag(0);
    recyclerView.setLayoutManager(horizontalLayoutManager);
    recyclerView.setAdapter(horizontalAdapter);
    recyclerView.setUp();

    return new ViewHolder(layoutView, recyclerView);
}
 

public void onChange(int index, String c, RecyclerView recyclerView) {
    if (recyclerView == null || letterMap == null) {
        return;
    }
    RecyclerView.LayoutManager lm = recyclerView.getLayoutManager();
    if (lm == null || !(lm instanceof LinearLayoutManager)) {
        return;
    }
    LinearLayoutManager manager = (LinearLayoutManager) lm;
    if (index == 0) {
        manager.scrollToPositionWithOffset(0, 0);//置顶
        return;
    }
    int[] value = letterMap.get(c);
    if (value != null) {
        manager.scrollToPositionWithOffset(value[0] + 2, 0);//+1 refresh header、+1 header
    }
}
 

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId()==R.id.action_favorite){
        final LocalDate localDate=LocalDate.now();

       final LinearLayoutManager linearLayoutManager= (LinearLayoutManager) mNestedView.getLayoutManager();
       mNestedView.stopScroll();
        if (indextrack.containsKey(new LocalDate(localDate.getYear(),localDate.getMonthOfYear(),localDate.getDayOfMonth()))){

            final Integer val=indextrack.get(new LocalDate(localDate.getYear(),localDate.getMonthOfYear(),localDate.getDayOfMonth()));

           if (isAppBarExpanded()){
               calendarView.setCurrentmonth(new LocalDate());
               expandedfirst=val;
               topspace=20;
               linearLayoutManager.scrollToPositionWithOffset(val,20);
               EventBus.getDefault().post(new MonthChange(localDate,0));
               month=localDate.getDayOfMonth();
               lastdate=localDate;
           }
           else {
               calendarView.setCurrentmonth(new LocalDate());
               expandedfirst=val;
               topspace=20;
               linearLayoutManager.scrollToPositionWithOffset(val,20);
               EventBus.getDefault().post(new MonthChange(localDate,0));
               month=localDate.getDayOfMonth();
               lastdate=localDate;

           }


        }

    }
    return super.onOptionsItemSelected(item);

}
 

private void initLocalRecycler() {
    mLocalSongsList = new ArrayList<>();
    layoutManager = new LinearLayoutManager(getActivity());
    mLocalSongsList.clear();
    mLocalSongsList.addAll(LitePal.findAll(LocalSong.class));
    if (mLocalSongsList.size() == 0) {
        mRecycler.setVisibility(View.GONE);
        mEmptyViewLinear.setVisibility(View.VISIBLE);
    } else {
        mEmptyViewLinear.setVisibility(View.GONE);
        mRecycler.setVisibility(View.VISIBLE);
        mRecycler.setLayoutManager(layoutManager);
        //令recyclerView定位到当前播放的位置
        songAdapter = new SongAdapter(mActivity, mLocalSongsList);
        mRecycler.setAdapter(songAdapter);
        if (FileUtil.getSong() != null) {
            layoutManager.scrollToPositionWithOffset(FileUtil.getSong().getPosition() - 4, mRecycler.getHeight());
        }
        songAdapter.setOnItemClickListener(position -> {
            //将点击的序列化到本地
            LocalSong mp3Info = mLocalSongsList.get(position);
            Song song = new Song();
            song.setSongName(mp3Info.getName());
            song.setSinger(mp3Info.getSinger());
            song.setUrl(mp3Info.getUrl());
            song.setDuration(mp3Info.getDuration());
            song.setPosition(position);
            song.setOnline(false);
            song.setSongId(mp3Info.getSongId());
            song.setListType(Constant.LIST_TYPE_LOCAL);
            FileUtil.saveSong(song);
            mPlayStatusBinder.play(Constant.LIST_TYPE_LOCAL);
        });

    }
}
 

@Override
public void onLeftItemSelected(int position, ModelDishMenu menu) {
    int sum = 0;
    for (int i = 0; i < position; i++) {
        sum += mModelDishMenuList.get(i).getModelDishList().size() + 1;
    }
    LinearLayoutManager layoutManager = (LinearLayoutManager) mRightMenu.getLayoutManager();
    layoutManager.scrollToPositionWithOffset(sum, 0);
    leftClickType = true;
}
 

/**
 * Maps the touch (from 0..1) to the adapter position that should be visible.
 */
@Override
public String scrollToPositionAtProgress(float touchFraction) {
    // Skip early if widgets are not bound.
    if (mWidgets == null) {
        return "";
    }

    // Skip early if there are no widgets.
    int rowCount = mWidgets.getPackageSize();
    if (rowCount == 0) {
        return "";
    }

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

    getCurScrollState(mScrollPosState);
    float pos = rowCount * touchFraction;
    int availableScrollHeight = getAvailableScrollHeight(rowCount, mScrollPosState.rowHeight);
    LinearLayoutManager layoutManager = ((LinearLayoutManager) getLayoutManager());
    layoutManager.scrollToPositionWithOffset(0, (int) -(availableScrollHeight * touchFraction));

    int posInt = (int) ((touchFraction == 1)? pos -1 : pos);
    PackageItemInfo p = mWidgets.getPackageItemInfo(posInt);
    return p.titleSectionName;
}
 

public static void scrollToPosition(RecyclerView recyclerView, int position) {
    LinearLayoutManager lm = (LinearLayoutManager) recyclerView.getLayoutManager();
    int recyclerWidth = recyclerView.getWidth();


    View itemView = lm.findViewByPosition(position);
    if (itemView != null) {
        int viewWidth = itemView.getWidth();
        lm.scrollToPositionWithOffset(position, -(recyclerWidth - viewWidth) / 2);
    }
}
 

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.getWindow().setBackgroundDrawableResource(android.R.color.transparent);
    setContentView(R.layout.activity_recycler);
    setSupportActionBar((Toolbar) findViewById(R.id.toolbar));
    mRvPostLister = (RecyclerView) findViewById(R.id.rv_post_list);
    final LinearLayoutManager manager = new LinearLayoutManager(this);
    mRvPostLister.setLayoutManager(manager);
    mPostList = new ArrayList<>();
    for (int i = 0; i < 29; i++) {
        List<UserViewInfo> imgUrls = new ArrayList<>();
        UserViewInfo userViewInfo;
        Random ss=new Random();

        for (int j = 0; j <ss.nextInt(9); j++) {
            userViewInfo=new UserViewInfo(     ImageUrlConfig.getUrls().get(j));
            imgUrls.add(userViewInfo);
        }
        Post post = new Post("Am I handsome? Am I handsome? Am I handsome?", imgUrls);
        mPostList.add(post);
    }

    mNineImageAdapter = new PostAdapter(this, mPostList, NineGridImageView.STYLE_GRID);
    mRvPostLister.setAdapter(mNineImageAdapter);
    manager.scrollToPositionWithOffset(5, 0);
    mRvPostLister.post(new Runnable() {
        @Override
        public void run() {
            View view = manager.findViewByPosition(1);
            if (view != null) System.out.println(view.getMeasuredHeight());
        }
    });
}
 

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

    mPlayingQueueAdapter = new PlayingQueueAdapter(
            (AppCompatActivity) getActivity(),
            MusicPlayerRemote.getPlayingQueue(),
            MusicPlayerRemote.getPosition(),
            R.layout.item_list,
            false,
            null);
    mWrappedAdapter = mRecyclerViewDragDropManager.createWrappedAdapter(mPlayingQueueAdapter);

    mLayoutManager = new LinearLayoutManager(getContext());

    mRecyclerView.setLayoutManager(mLayoutManager);
    mRecyclerView.setAdapter(mWrappedAdapter);
    mRecyclerView.setItemAnimator(animator);

    mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
               /* if (recyclerView.canScrollVertically(RecyclerView.NO_POSITION)) {
                    mAppBarLayout.setElevation(5f);
                } else {
                    mAppBarLayout.setElevation(0f);
                }*/
            }
        }
    });

    mRecyclerViewDragDropManager.attachRecyclerView(mRecyclerView);
    mLayoutManager.scrollToPositionWithOffset(MusicPlayerRemote.getPosition() + 1, 0);
}
 

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.getWindow().setBackgroundDrawableResource(android.R.color.transparent);
    setContentView(R.layout.activity_recycler);
    setSupportActionBar((Toolbar) findViewById(R.id.toolbar));

    mRvPostLister = (RecyclerView) findViewById(R.id.rv_post_list);
    final LinearLayoutManager manager = new LinearLayoutManager(this);
    mRvPostLister.setLayoutManager(manager);

    mPostList = new ArrayList<>();
    for (int i = 0; i < 18; i++) {
        List<String> imgUrls = new ArrayList<>();
        imgUrls.addAll(Arrays.asList(IMG_URL_LIST).subList(0, i % 9));
        Post post = new Post("Am I handsome? Am I handsome? Am I handsome?", imgUrls);
        mPostList.add(post);
    }

    mNineImageAdapter = new PostAdapter(this, mPostList, NineGridImageView.STYLE_GRID);
    mRvPostLister.setAdapter(mNineImageAdapter);

    manager.scrollToPositionWithOffset(5, 0);
    mRvPostLister.post(new Runnable() {
        @Override
        public void run() {
            View view = manager.findViewByPosition(1);
            if (view != null) System.out.println(view.getMeasuredHeight());
        }
    });
}
 

/**
 * Maps the touch (from 0..1) to the adapter position that should be visible.
 */
@Override
public String scrollToPositionAtProgress(float touchFraction) {
    int rowCount = mApps.getNumAppRows();
    if (rowCount == 0) {
        return "";
    }

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

    // Find the fastscroll section that maps to this touch fraction
    List<AlphabeticalAppsList.FastScrollSectionInfo> fastScrollSections =
            mApps.getFastScrollerSections();
    AlphabeticalAppsList.FastScrollSectionInfo lastInfo = fastScrollSections.get(0);
    if (mScrollBarMode == FAST_SCROLL_BAR_MODE_DISTRIBUTE_BY_ROW) {
        for (int i = 1; i < fastScrollSections.size(); i++) {
            AlphabeticalAppsList.FastScrollSectionInfo info = fastScrollSections.get(i);
            if (info.touchFraction > touchFraction) {
                break;
            }
            lastInfo = info;
        }
    } else if (mScrollBarMode == FAST_SCROLL_BAR_MODE_DISTRIBUTE_BY_SECTIONS){
        lastInfo = fastScrollSections.get((int) (touchFraction * (fastScrollSections.size() - 1)));
    } else {
        throw new RuntimeException("Unexpected scroll bar mode");
    }

    // Reset the last focused section
    if (mPrevFastScrollFocusedSection != lastInfo.sectionInfo) {
        setSectionFastScrollDimmed(mPrevFastScrollFocusedPosition, true, true);
        clearSectionFocusedItems();
    }

    mPrevFastScrollFocusedPosition = lastInfo.fastScrollToItem.position;
    mPrevFastScrollFocusedSection = lastInfo.sectionInfo;

    getCurScrollState(mScrollPosState);
    if (mFastScrollMode == FAST_SCROLL_MODE_JUMP_TO_FIRST_ICON) {
        smoothSnapToPosition(mPrevFastScrollFocusedPosition, mScrollPosState);

        setSectionFastScrollDimmed(mPrevFastScrollFocusedPosition, false, true);
        setSectionFastScrollFocused(mPrevFastScrollFocusedPosition);
    } else if (mFastScrollMode == FAST_SCROLL_MODE_FREE_SCROLL) {
        // Map the touch position back to the scroll of the recycler view
        int availableScrollHeight = getAvailableScrollHeight(rowCount, mScrollPosState.rowHeight);
        LinearLayoutManager layoutManager = (LinearLayoutManager) getLayoutManager();
        layoutManager.scrollToPositionWithOffset(0, (int) -(availableScrollHeight * touchFraction));

        setSectionFastScrollFocused(mPrevFastScrollFocusedPosition);
    } else {
        throw new RuntimeException("Unexpected fast scroll mode");
    }
    return lastInfo.sectionName;
}
 

/**
 * <p>Maps the touch (from 0..1) to the adapter position that should be visible.</p>
 *
 * <p>Override in each subclass of this base class.</p>
 */
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(scrollPositionState);

  float itemPos = itemCount * touchFraction;

  int availableScrollHeight = getAvailableScrollHeight(rowCount, scrollPositionState.rowHeight);

  //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 / scrollPositionState.rowHeight,
      -(exactItemPos % scrollPositionState.rowHeight));

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

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

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

public void scrollToPosition(int posi, int top) {
    LinearLayoutManager layoutManager = (LinearLayoutManager) mRvScroll.getLayoutManager();
    layoutManager.scrollToPositionWithOffset(posi - 1, top);// -1==>Starting from 0 to calculate
}
 

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

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

		int itemCount = recyclerView.getAdapter().getItemCount();
		float proportion = getValueInRange(0, 1f, y / (float) height);

		float targetPosFloat = getValueInRange(0, 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.getChildPosition(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);
}