react-native/React/Views/RCTScrollView.h
rxb dcf245a9a2 Definable distance pagination for ScrollView
Summary: This is an enhancement for ScrollView that adds the ability to paginate based on a width other than the width of the ScrollView itself. This is a fairly common pattern used on apps like Facebook, App Store, and Twitter to scroll through a horizontal set of cards or icons:

![img_8726 2](https://cloud.githubusercontent.com/assets/451050/8017899/39f9f47c-0bd2-11e5-9c1d-889452f20cf7.PNG) ![img_8727 2](https://cloud.githubusercontent.com/assets/451050/8017898/39f962dc-0bd2-11e5-98b4-461ac0f7f21b.PNG)  ![img_8728 2](https://cloud.githubusercontent.com/assets/451050/8017900/39fd91a4-0bd2-11e5-8786-4cf0316295a0.PNG)

After trying to accomplish this only with JS, it appears that attempting to take over an in-progress native scroll animation with JS is always going to result in some amount of jankiness and jumping.

This pull request uses `scrollViewWillEndDragging` in RCTScrollView.m to adjust `targetContentOffset` based on two new optional props added to ScrollView. `snapToInterval` sets the multiple that the
Closes https://github.com/facebook/react-native/pull/1532

Reviewed By: @​svcscm, @​trunkagent

Differential Revision: D2443701

Pulled By: @vjeux
2015-09-23 11:47:25 -07:00

65 lines
2.2 KiB
Objective-C

/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*/
#import <UIKit/UIScrollView.h>
#import "RCTAutoInsetsProtocol.h"
#import "RCTEventDispatcher.h"
#import "RCTScrollableProtocol.h"
#import "RCTView.h"
@protocol UIScrollViewDelegate;
@interface RCTScrollView : RCTView <UIScrollViewDelegate, RCTScrollableProtocol, RCTAutoInsetsProtocol>
- (instancetype)initWithEventDispatcher:(RCTEventDispatcher *)eventDispatcher NS_DESIGNATED_INITIALIZER;
/**
* The `RCTScrollView` may have at most one single subview. This will ensure
* that the scroll view's `contentSize` will be efficiently set to the size of
* the single subview's frame. That frame size will be determined somewhat
* efficiently since it will have already been computed by the off-main-thread
* layout system.
*/
@property (nonatomic, readonly) UIView *contentView;
/**
* If the `contentSize` is not specified (or is specified as {0, 0}, then the
* `contentSize` will automatically be determined by the size of the subview.
*/
@property (nonatomic, assign) CGSize contentSize;
/**
* The underlying scrollView (TODO: can we remove this?)
*/
@property (nonatomic, readonly) UIScrollView *scrollView;
@property (nonatomic, assign) UIEdgeInsets contentInset;
@property (nonatomic, assign) BOOL automaticallyAdjustContentInsets;
@property (nonatomic, assign) NSTimeInterval scrollEventThrottle;
@property (nonatomic, assign) BOOL centerContent;
@property (nonatomic, assign) int snapToInterval;
@property (nonatomic, copy) NSString *snapToAlignment;
@property (nonatomic, copy) NSIndexSet *stickyHeaderIndices;
@end
@interface RCTEventDispatcher (RCTScrollView)
/**
* Send a scroll event.
* (You can send a fake scroll event by passing nil for scrollView).
*/
- (void)sendScrollEventWithType:(RCTScrollEventType)type
reactTag:(NSNumber *)reactTag
scrollView:(UIScrollView *)scrollView
userData:(NSDictionary *)userData;
@end