androidx.recyclerview.widget.RecyclerView#post ( )源码实例Demo

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView recyclerView, RecyclerView.State state) {
    if (mCallback == null || !mEnabled) return;

    int adapterPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewAdapterPosition();
    int itemCount = recyclerView.getAdapter().getItemCount();
    // RecyclerView.Adapter getItemCount gives count of values + 1 (PaginationViewHolder)
    int preventionPosition = itemCount - mCallback.getPagePreventionForEnd() - 1;
    if (adapterPosition >= preventionPosition && itemCount > mLastItemCount) {
        mCurrentPage++;
        recyclerView.post(new Runnable() {
            @Override
            public void run() {
                mCallback.onPageRequest(mCurrentPage);
            }
        });
        mLastItemCount = itemCount;
    }
}
 

@Override
public void onScrolled(@NonNull RecyclerView recyclerView, int dx, final int dy) {
    recyclerView.post(() -> {
        if (!canScrollVertically(1) && dy > 0)
            if (getAdapter() instanceof InfiniteAdapter)
                ((InfiniteAdapter) getAdapter()).loadMoreContent();
    });
}
 

@Override
protected boolean attach(RecyclerView recyclerView) {
    if (recyclerView != null) {
        recyclerView.addOnScrollListener(this);
        recyclerView.post(new Runnable() {
            @Override
            public void run() {
                onScroll();
            }
        });
    }

    return true;
}
 

@Override
public void onScrolled(RecyclerView view, int dx, int dy) {

	// no-op if we're loading, or exhausted
	if (loading || loadExhausted) {
		return;
	}

	// If the total item count is zero and the previous isn't, assume the
	// list is invalidated and should be reset back to initial state
	int totalItemCount = layoutManager.getItemCount();
	if (totalItemCount < previousTotalItemCount) {
		this.currentPage = 0;
		this.previousTotalItemCount = totalItemCount;
	} else if (totalItemCount > 0) {

		View lastVisibleItem = layoutManager.getBottommostChildView();
		int lastVisibleItemAdapterPosition = layoutManager.getViewAdapterPosition(lastVisibleItem);

		if ((lastVisibleItemAdapterPosition + visibleThreshold) > totalItemCount) {
			currentPage++;
			loading = true;

			view.post(new Runnable() {
				@Override
				public void run() {
					onLoadMore(currentPage, loadCompleteNotifier);
				}
			});
		}
	}
}
 

private void loadNextItemsIfNeeded(RecyclerView recyclerView) {
    if (!isLoading && !isError) {
        View lastVisibleChild = recyclerView.getChildAt(recyclerView.getChildCount() - 1);
        int lastVisiblePos = recyclerView.getChildAdapterPosition(lastVisibleChild);
        int total = getItemCount();

        if (lastVisiblePos >= total - loadingOffset) {
            // We need to use runnable, since recycler view does not like when we are notifying
            // about changes during scroll callback.
            recyclerView.post(this::loadNextItems);
        }
    }
}
 

private void scrollListToTop(final RecyclerView recyclerView) {
    recyclerView.post(() -> recyclerView.scrollToPosition(0));
}
 

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.activity_card_display_manage);

    Toolbar toolbar = findViewById(R.id.activity_card_display_manage_toolbar);
    toolbar.setNavigationIcon(R.drawable.ic_toolbar_back);
    toolbar.setNavigationOnClickListener(view -> finish());

    List<CardDisplay> displayCards = SettingsOptionManager.getInstance(this).getCardDisplayList();
    cardDisplayAdapter = new CardDisplayAdapter(displayCards, cardDisplay -> {
        setResult(RESULT_OK);
        tagAdapter.insertItem(new CardTag(cardDisplay));
        resetBottomBarVisibility();
    });

    RecyclerView recyclerView = findViewById(R.id.activity_card_display_manage_recyclerView);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    recyclerView.addItemDecoration(new ListDecoration(this));
    recyclerView.setAdapter(cardDisplayAdapter);

    new ItemTouchHelper(
            new CardDisplaySwipeCallback(
                    ItemTouchHelper.UP | ItemTouchHelper.DOWN,
                    ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT
            )
    ).attachToRecyclerView(recyclerView);

    List<CardDisplay> otherCards = new ArrayList<>();
    otherCards.add(CardDisplay.CARD_DAILY_OVERVIEW);
    otherCards.add(CardDisplay.CARD_HOURLY_OVERVIEW);
    otherCards.add(CardDisplay.CARD_AIR_QUALITY);
    otherCards.add(CardDisplay.CARD_ALLERGEN);
    otherCards.add(CardDisplay.CARD_SUNRISE_SUNSET);
    otherCards.add(CardDisplay.CARD_LIFE_DETAILS);
    for (int i = otherCards.size() - 1; i >= 0; i --) {
        for (int j = 0; j < displayCards.size(); j ++) {
            if (otherCards.get(i) == displayCards.get(j)) {
                otherCards.remove(i);
                break;
            }
        }
    }
    List<TagAdapter.Tag> tagList = new ArrayList<>();
    for (CardDisplay card : otherCards) {
        tagList.add(new CardTag(card));
    }
    tagAdapter = new TagAdapter(this, tagList, (checked, oldPosition, newPosition) -> {
        setResult(RESULT_OK);
        CardTag tag = (CardTag) tagAdapter.removeItem(newPosition);
        cardDisplayAdapter.insertItem(tag.card);
        resetBottomBarVisibility();
        return true;
    });

    bottomBar = findViewById(R.id.activity_card_display_manage_bottomBar);
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT_WATCH) {
        bottomBar.setOnApplyWindowInsetsListener((v, insets) -> {
            bottomBar.setPadding(0, 0, 0, insets.getSystemWindowInsetBottom());
            return insets;
        });
    }

    RecyclerView bottomRecyclerView = findViewById(R.id.activity_card_display_manage_bottomRecyclerView);
    bottomRecyclerView.setLayoutManager(
            new LinearLayoutManager(this, RecyclerView.HORIZONTAL, false));
    bottomRecyclerView.addItemDecoration(
            new GridMarginsDecoration(
                    getResources().getDimension(R.dimen.normal_margin), bottomRecyclerView
            )
    );
    bottomRecyclerView.setAdapter(tagAdapter);

    bottomAnimator = null;
    bottomBarVisibility = false;
    bottomRecyclerView.post(this::resetBottomBarVisibility);
}
 

@SuppressLint("InflateParams")
public View createView(int titleTextColor, int backgroundDrawable, int backgroundColor,
                       int dividerBackground, int itemTextColor, int itemBackground,
                       int tintColor, BottomSheetItemClickListener itemClickListener) {

    if (mFromMenu) {
        mItems = createAdapterItems(dividerBackground, titleTextColor,
                itemTextColor, itemBackground, tintColor);
    }

    LayoutInflater layoutInflater = LayoutInflater.from(mContext);

    View sheet = mMode == BottomSheetBuilder.MODE_GRID ?
            layoutInflater.inflate(R.layout.bottomsheetbuilder_sheet_grid, null)
            : layoutInflater.inflate(R.layout.bottomsheetbuilder_sheet_list, null);

    final RecyclerView recyclerView = (RecyclerView) sheet.findViewById(R.id.recyclerView);
    recyclerView.setHasFixedSize(true);

    if (backgroundDrawable != 0) {
        sheet.setBackgroundResource(backgroundDrawable);
    } else {
        if (backgroundColor != 0) {
            sheet.setBackgroundColor(backgroundColor);
        }
    }

    // If we only have one title and it's the first item, set it as fixed
    if (mTitles == 1 && mMode == BottomSheetBuilder.MODE_LIST) {
        BottomSheetItem header = mItems.get(0);
        TextView headerTextView = (TextView) sheet.findViewById(R.id.textView);
        if (header instanceof BottomSheetHeader) {
            headerTextView.setVisibility(View.VISIBLE);
            headerTextView.setText(header.getTitle());
            if (titleTextColor != 0) {
                headerTextView.setTextColor(titleTextColor);
            }
            mItems.remove(0);
        }
    }

    final BottomSheetItemAdapter adapter = new BottomSheetItemAdapter(mItems, mMode,
            itemClickListener);

    if (mMode == BottomSheetBuilder.MODE_LIST) {
        recyclerView.setLayoutManager(new LinearLayoutManager(mContext));
        recyclerView.setAdapter(adapter);
    } else {
        final int columns = mContext.getResources().getInteger(R.integer.bottomsheet_grid_columns);
        GridLayoutManager layoutManager = new GridLayoutManager(mContext, columns);
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.post(new Runnable() {
            @Override
            public void run() {
                float margin = mContext.getResources()
                        .getDimensionPixelSize(R.dimen.bottomsheet_grid_horizontal_margin);
                adapter.setItemWidth((int) ((recyclerView.getWidth() - 2 * margin) / columns));
                recyclerView.setAdapter(adapter);
            }
        });
    }

    return sheet;
}