DreamingInBinary · August 14, 2018 20:10 · Aug 14, 2018
diff --git a/UIView+BFRShimmering.m b/UIView+BFRShimmering.m
@@ -0,0 +1,115 @@
+//
+//  UIView+BFRShimmer.h
+//  BFRUtils
+//
+//  Created by Jordan Morgan on 8/14/18.
+//  Copyright © 2018 Buffer. All rights reserved.
+//
+
+#import <UIKit/UIKit.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface UIView (BFRShimmer)
+
+@property (strong, nonatomic, readonly, nonnull) CAGradientLayer *gradient;
+@property (strong, nonatomic, readonly, nonnull) CABasicAnimation *shimmerAnimation;
+
+- (void)startShimmering;
+- (void)startShimmeringWithRepitions:(NSInteger)reps;
+- (void)endShimmering;
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+
+//
+//  UIView+BFRShimmer.m
+//  BFRUtils
+//
+//  Created by Jordan Morgan on 8/14/18.
+//  Copyright © 2018 Buffer. All rights reserved.
+//
+
+#import "UIView+BFRShimmer.h"
+#import <objc/runtime.h>
+
+static NSString * const BFR_SHIMMER_KEY = @"bfr.Shimmering.animationKey";
+
+@implementation UIView (BFRShimmer)
+
+#pragma mark - Dynamic Properties
+
+static const void *GradientKey = &GradientKey;
+static const void *AnimationKey = &AnimationKey;
+
+- (CAGradientLayer *)gradient {
+    CAGradientLayer *returnVal = objc_getAssociatedObject(self, GradientKey);
+
+    if (!returnVal) {
+        returnVal = [CAGradientLayer new];
+        objc_setAssociatedObject(self, GradientKey, returnVal, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+    }
+
+    return returnVal;
+}
+
+- (CABasicAnimation *)shimmerAnimation {
+    CABasicAnimation *returnVal = objc_getAssociatedObject(self, AnimationKey);
+
+    if (!returnVal) {
+        returnVal = [CABasicAnimation animationWithKeyPath:@"position"];
+        objc_setAssociatedObject(self, AnimationKey, returnVal, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+    }
+
+    return returnVal;
+}
+
+#pragma mark - Public API
+
+- (void)startShimmeringWithRepitions:(NSInteger)reps {
+    [CATransaction begin];
+    [CATransaction setCompletionBlock:^{
+        [self endShimmering];
+    }];
+
+    UIColor *lightColor = [[UIColor whiteColor] colorWithAlphaComponent:0.1];
+    UIColor *darkColor = [[UIColor blackColor] colorWithAlphaComponent:1.0];
+
+    CGFloat length = CGRectGetWidth(self.layer.bounds);
+    CGFloat extraDistance = length + 1.0f * 0.4f;
+    CGFloat fullShimmerLength = length * 3.0f + extraDistance;
+    CGFloat travelDistance = length * 2.0f + extraDistance;
+    CGFloat highlightOutsideLength = 0.0 / 2.0;
+    CGFloat startPoint = (length + extraDistance) / fullShimmerLength;
+    CGFloat endPoint = travelDistance / fullShimmerLength;
+
+    self.gradient.bounds = CGRectMake(0.0, 0.0, fullShimmerLength, CGRectGetHeight(self.layer.bounds));
+    self.gradient.position = CGPointMake(-travelDistance, 0.0);
+    self.gradient.anchorPoint = CGPointZero;
+    self.gradient.startPoint = CGPointMake(startPoint, 0.0);
+    self.gradient.endPoint = CGPointMake(endPoint, 0.0);
+    self.gradient.locations = @[@(highlightOutsideLength), @(0.5), @(1.0 - highlightOutsideLength)];
+    self.gradient.colors = @[(id)darkColor.CGColor, (id)lightColor.CGColor, (id)darkColor.CGColor];
+
+    self.shimmerAnimation.duration = 1.0;
+    self.shimmerAnimation.repeatCount = reps > 0 ? reps : INFINITY;
+    self.shimmerAnimation.toValue = [NSValue valueWithCGPoint:CGPointZero];
+
+    [self.gradient addAnimation:self.shimmerAnimation forKey:BFR_SHIMMER_KEY];
+    self.layer.mask = self.gradient;
+
+    [CATransaction commit];
+}
+- (void)startShimmering {
+    [self startShimmeringWithRepitions:0];
+}
+
+- (void)endShimmering {
+    [self.layer.mask removeAnimationForKey:BFR_SHIMMER_KEY];
+    self.layer.mask = nil;
+    [self.layer setNeedsDisplay];
+}
+
+@end