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AppSwitchScrollStopper
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// UIWindow+AppSwitchScrollStopper.h | |
// Created by Tim Johnsen on 3/27/16. | |
#import <UIKit/UIKit.h> | |
@interface UIWindow (AppSwitchScrollStopper) | |
/// Call this early on in your app's lifecycle to avoid | |
/// scroll-related flashing when your app resumes from the background | |
- (void)installAppSwitchScrollStopper; | |
@end |
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// UIWindow+AppSwitchScrollStopper.m | |
// Created by Tim Johnsen on 3/27/16. | |
#import "UIWindow+AppSwitchScrollStopper.h" | |
@interface UIView (AppSwitchScrollStopper) | |
- (void)recursiveStopScrolling; | |
@end | |
@implementation UIView (AppSwitchScrollStopper) | |
- (void)recursiveStopScrolling | |
{ | |
if ([self isKindOfClass:[UIScrollView class]]) { | |
UIScrollView *scrollView = (UIScrollView *)self; | |
// Stop the scrolling (http://stackoverflow.com/a/3421387/3943258) | |
[scrollView setContentOffset:scrollView.contentOffset animated:NO]; | |
// Stop the scroll indicators from being captured | |
if (scrollView.showsHorizontalScrollIndicator) { | |
scrollView.showsHorizontalScrollIndicator = NO; | |
scrollView.showsHorizontalScrollIndicator = YES; | |
} | |
if (scrollView.showsVerticalScrollIndicator) { | |
scrollView.showsVerticalScrollIndicator = NO; | |
scrollView.showsVerticalScrollIndicator = YES; | |
} | |
} | |
for (UIView *view in self.subviews) { | |
[view recursiveStopScrolling]; | |
} | |
} | |
@end | |
@implementation UIWindow (AppSwitchScrollStopper) | |
+ (void)load | |
{ | |
void (^stopScrollingBlock)(NSNotification *_Nonnull notification) = ^(NSNotification *_Nonnull notification) { | |
for (UIWindow *window in [self windowsToStopScrolling]) { | |
[window recursiveStopScrolling]; | |
} | |
}; | |
[[NSNotificationCenter defaultCenter] addObserverForName:UIApplicationDidEnterBackgroundNotification object:nil queue:[NSOperationQueue mainQueue] usingBlock:stopScrollingBlock]; | |
// Works in iOS extensions too! | |
if (&NSExtensionHostDidEnterBackgroundNotification) { | |
[[NSNotificationCenter defaultCenter] addObserverForName:NSExtensionHostDidEnterBackgroundNotification object:nil queue:[NSOperationQueue mainQueue] usingBlock:stopScrollingBlock]; | |
} | |
} | |
+ (NSMutableSet<UIWindow *> *)windowsToStopScrolling | |
{ | |
static NSMutableSet<UIWindow *> *windowsToStopScrolling = nil; | |
static dispatch_once_t onceToken; | |
dispatch_once(&onceToken, ^{ | |
windowsToStopScrolling = [NSMutableSet new]; | |
}); | |
return windowsToStopScrolling; | |
} | |
- (void)installAppSwitchScrollStopper | |
{ | |
[[[self class] windowsToStopScrolling] addObject:self]; | |
} | |
@end |
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