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7dd94a6102
Introduce `ASTableView`, a UITableView subclass that uses `ASCellNode` instead of UITableViewCell. Add working range support via `ASRangeController`, which observes the visible range, maintains a working range, and handles most ASDK machinery. ASRangeController is loosely-enough coupled that it should be easily adapted to UICollectionView if that's desired in the future. Notable considerations in the ASRangeController architecture: * There's no sense rewriting UITableView -- the real win comes from using nodes instead of UITableViewCells (easily parallelisable computation, large number of cells vs. few table views, etc.). So, use a UITableView with empty cells, using UITableViewCell's contentView as a host for arbitrary node hierarchies. * Instead of lazy-loading cells the instant they're needed by UITableView, load them in advance. Preload a substantial number of nodes in the direction of scroll, as well as a small buffer in the other direction. * Maintain compatibility with UITableView's API, with one primary change -- consumer code yields configured ASCellNodes, not UITableViewCells. * Don't use -tableView:heightForRowAtIndexPath:. Nodes already compute their preferred sizes and cache results for use at layout-time, so ASTableView uses their calculatedSizes directly. * Corollary: ASTableView is only aware of nodes that have been sized. This means that, if a cell appears onscreen, it has layout data and can display a "realistic placeholder", e.g. by making its subnodes' background colour grey. Other improvements: * Remove dead references and update headers (fixes #7, #20). * Rename `-[ASDisplayNode sizeToFit:]` to `-measure:` and fix `constrainedSizeForCalulatedSize` typo (fixes #15). * Rename `-willAppear` and `-didDisappear` to `-willEnterHierarchy` and `-didExitHierarchy`. Remove `-willDisappear` -- it was redundant, and there was no counterpart `-didAppear`. * Rename `viewLoaded` to `nodeLoaded`.
118 lines
4.1 KiB
Objective-C
118 lines
4.1 KiB
Objective-C
/* Copyright (c) 2014-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*/
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#import <Foundation/Foundation.h>
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#import <AsyncDisplayKit/ASCellNode.h>
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typedef struct {
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// working range buffers, on either side of scroll
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NSInteger trailingBufferScreenfuls;
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NSInteger leadingBufferScreenfuls;
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} ASRangeTuningParameters;
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@protocol ASRangeControllerDelegate;
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/**
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* Working range controller.
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*
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* Used internally by ASTableView and potentially by a future ASCollectionView. Observes the visible range, maintains
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* a working range, and is responsible for handling AsyncDisplayKit machinery (sizing cell nodes, enqueueing and
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* cancelling their asynchronous layout and display, and so on).
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*/
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@interface ASRangeController : NSObject
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/**
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* Notify the receiver that its delegate's data source has been set or changed. This is like -[UITableView reloadData]
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* but drastically more expensive, as it destroys the working range and all cached nodes.
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*/
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- (void)rebuildData;
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/**
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* Notify the receiver that the visible range has been updated.
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*
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* @see -rangeControllerVisibleNodeIndexPaths:
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*/
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- (void)visibleNodeIndexPathsDidChange;
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/**
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* ASTableView is only aware of nodes that have already been sized.
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*
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* Custom ASCellNode implementations are encouraged to have "realistic placeholders", since they can only be onscreen if
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* they have enough data for layout. E.g., try setting all subnodes' background colours to [UIColor lightGrayColor].
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*/
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- (NSInteger)numberOfSizedSections;
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- (NSInteger)numberOfSizedRowsInSection:(NSInteger)section;
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/**
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* Add the sized node for `indexPath` as a subview of `contentView`.
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*/
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- (void)configureContentView:(UIView *)contentView forIndexPath:(NSIndexPath *)indexPath;
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/**
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* Query the sized node at `indexPath` for its calculatedSize.
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*
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* TODO: Currently we disallow direct access to ASCellNode outside ASRangeController since touching the node's view can
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* break async display. We should expose the node anyway, possibly with an assertion guarding against external
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* use of the view property, so ASCellNode can support configuration for UITableViewCell properties (selection
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* style, separator style, etc.) and ASTableView can query that data.
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*/
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- (CGSize)calculatedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath;
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/**
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* Notify the receiver that its data source has been updated to append the specified nodes.
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*/
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- (void)appendNodesWithIndexPaths:(NSArray *)indexPaths;
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/**
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* Delegate and ultimate data source. Must not be nil.
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*/
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@property (nonatomic, weak) id<ASRangeControllerDelegate> delegate;
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/**
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* Tuning parameters for the working range.
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*
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* Defaults to a trailing buffer of one screenful and a leading buffer of two screenfuls.
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*/
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@property (nonatomic, assign) ASRangeTuningParameters tuningParameters;
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@end
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@protocol ASRangeControllerDelegate <NSObject>
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/**
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* @returns an array of index paths corresponding to the nodes currently visible onscreen (i.e., the visible range).
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*/
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- (NSArray *)rangeControllerVisibleNodeIndexPaths:(ASRangeController *)rangeController;
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/**
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* @returns the receiver's viewport size (i.e., the screen space occupied by the visible range).
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*/
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- (CGSize)rangeControllerViewportSize:(ASRangeController *)rangeController;
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/**
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* Forwarded to ASTableView's data source.
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*/
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- (NSInteger)rangeControllerSections:(ASRangeController *)rangeController;
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- (NSInteger)rangeController:(ASRangeController *)rangeController rowsInSection:(NSInteger)section;
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- (ASCellNode *)rangeController:(ASRangeController *)rangeController nodeForIndexPath:(NSIndexPath *)indexPath;
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/**
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* @returns sizing constraints for the node at `indexPath`.
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*/
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- (CGSize)rangeController:(ASRangeController *)rangeController constrainedSizeForNodeAtIndexPath:(NSIndexPath *)indexPath;
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/**
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* Notifies the receiver that the specified nodes have been sized and are ready for display.
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*/
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- (void)rangeController:(ASRangeController *)rangeController didSizeNodesWithIndexPaths:(NSArray *)indexPaths;
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@end
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