Janic Duplessis 6c434f9404 Native Animated - Support decay on iOS
Summary:
This is one of the last feature that is missing from native animated, it was already supported on Android and this implementation is based on it.

**Test plan**
Test that the existing decay animation example now works on iOS
Run unit tests
Closes https://github.com/facebook/react-native/pull/13368

Differential Revision: D4938061

Pulled By: javache

fbshipit-source-id: 36b57b1029a542e9daf21e048a06d3b3347e9659
2017-04-24 04:31:43 -07:00

125 lines
3.2 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 "RCTDecayAnimation.h"
#import <UIKit/UIKit.h>
#import <React/RCTConvert.h>
#import "RCTValueAnimatedNode.h"
@interface RCTDecayAnimation ()
@property (nonatomic, strong) NSNumber *animationId;
@property (nonatomic, strong) RCTValueAnimatedNode *valueNode;
@property (nonatomic, assign) BOOL animationHasBegun;
@property (nonatomic, assign) BOOL animationHasFinished;
@end
@implementation RCTDecayAnimation
{
CGFloat _velocity;
CGFloat _deceleration;
NSTimeInterval _frameStartTime;
CGFloat _fromValue;
CGFloat _lastValue;
NSInteger _iterations;
NSInteger _currentLoop;
RCTResponseSenderBlock _callback;
}
- (instancetype)initWithId:(NSNumber *)animationId
config:(NSDictionary *)config
forNode:(RCTValueAnimatedNode *)valueNode
callBack:(nullable RCTResponseSenderBlock)callback;
{
if ((self = [super init])) {
NSNumber *iterations = [RCTConvert NSNumber:config[@"iterations"]] ?: @1;
_animationId = animationId;
_fromValue = 0;
_lastValue = 0;
_valueNode = valueNode;
_callback = [callback copy];
_velocity = [RCTConvert CGFloat:config[@"velocity"]];
_deceleration = [RCTConvert CGFloat:config[@"deceleration"]];
_iterations = iterations.integerValue;
_currentLoop = 1;
_animationHasFinished = iterations.integerValue == 0;
}
return self;
}
RCT_NOT_IMPLEMENTED(- (instancetype)init)
- (void)startAnimation
{
_frameStartTime = -1;
_animationHasBegun = YES;
}
- (void)stopAnimation
{
_valueNode = nil;
if (_callback) {
_callback(@[@{
@"finished": @(_animationHasFinished)
}]);
}
}
- (void)stepAnimationWithTime:(NSTimeInterval)currentTime
{
if (!_animationHasBegun || _animationHasFinished) {
// Animation has not begun or animation has already finished.
return;
}
if (_frameStartTime == -1) {
// Since this is the first animation step, consider the start to be on the previous frame.
_frameStartTime = currentTime - RCTSingleFrameInterval;
if (_fromValue == _lastValue) {
// First iteration, assign _fromValue based on _valueNode.
_fromValue = _valueNode.value;
} else {
// Not the first iteration, reset _valueNode based on _fromValue.
[self updateValue:_fromValue];
}
_lastValue = _valueNode.value;
}
CGFloat value = _fromValue +
(_velocity / (1 - _deceleration)) *
(1 - exp(-(1 - _deceleration) * (currentTime - _frameStartTime) * 1000.0));
[self updateValue:value];
if (fabs(_lastValue - value) < 0.1) {
if (_iterations == -1 || _currentLoop < _iterations) {
// Set _frameStartTime to -1 to reset instance variables on the next runAnimationStep.
_frameStartTime = -1;
_currentLoop++;
} else {
_animationHasFinished = true;
return;
}
}
_lastValue = value;
}
- (void)updateValue:(CGFloat)outputValue
{
_valueNode.value = outputValue;
[_valueNode setNeedsUpdate];
}
@end