Для этой цели я создал категорию для UIView
и внедрил совершенно другую концепцию: visibility
. Основное отличие моего решения заключается в том, что вы можете вызвать [view setVisible:NO animated:YES]
и сразу после этого синхронно проверить [view visible]
и получить правильный результат. Это довольно просто, но очень полезно.
Кроме того, разрешено избегать использования «отрицательной логической логики» (см. Code Complete, стр. 269, Использовать положительные имена переменных boolean для более информация).
UIView+Visibility.swift
import UIKit
private let UIViewVisibilityShowAnimationKey = "UIViewVisibilityShowAnimationKey"
private let UIViewVisibilityHideAnimationKey = "UIViewVisibilityHideAnimationKey"
private class UIViewAnimationDelegate: NSObject {
weak var view: UIView?
dynamic override func animationDidStop(animation: CAAnimation, finished: Bool) {
guard let view = self.view where finished else {
return
}
view.hidden = !view.visible
view.removeVisibilityAnimations()
}
}
extension UIView {
private func removeVisibilityAnimations() {
self.layer.removeAnimationForKey(UIViewVisibilityShowAnimationKey)
self.layer.removeAnimationForKey(UIViewVisibilityHideAnimationKey)
}
var visible: Bool {
get {
return !self.hidden && self.layer.animationForKey(UIViewVisibilityHideAnimationKey) == nil
}
set {
let visible = newValue
guard self.visible != visible else {
return
}
let animated = UIView.areAnimationsEnabled()
self.removeVisibilityAnimations()
guard animated else {
self.hidden = !visible
return
}
self.hidden = false
let delegate = UIViewAnimationDelegate()
delegate.view = self
let animation = CABasicAnimation(keyPath: "opacity")
animation.fromValue = visible ? 0.0 : 1.0
animation.toValue = visible ? 1.0 : 0.0
animation.fillMode = kCAFillModeForwards
animation.removedOnCompletion = false
animation.delegate = delegate
self.layer.addAnimation(animation, forKey: visible ? UIViewVisibilityShowAnimationKey : UIViewVisibilityHideAnimationKey)
}
}
func setVisible(visible: Bool, animated: Bool) {
let wereAnimationsEnabled = UIView.areAnimationsEnabled()
if wereAnimationsEnabled != animated {
UIView.setAnimationsEnabled(animated)
defer { UIView.setAnimationsEnabled(!animated) }
}
self.visible = visible
}
}
UIView+Visibility.h
#import
@interface UIView (Visibility)
- (BOOL)visible;
- (void)setVisible:(BOOL)visible;
- (void)setVisible:(BOOL)visible animated:(BOOL)animated;
@end
UIView+Visibility.m
#import "UIView+Visibility.h"
NSString *const UIViewVisibilityAnimationKeyShow = @"UIViewVisibilityAnimationKeyShow";
NSString *const UIViewVisibilityAnimationKeyHide = @"UIViewVisibilityAnimationKeyHide";
@implementation UIView (Visibility)
- (BOOL)visible
{
if (self.hidden || [self.layer animationForKey:UIViewVisibilityAnimationKeyHide]) {
return NO;
}
return YES;
}
- (void)setVisible:(BOOL)visible
{
[self setVisible:visible animated:NO];
}
- (void)setVisible:(BOOL)visible animated:(BOOL)animated
{
if (self.visible == visible) {
return;
}
[self.layer removeAnimationForKey:UIViewVisibilityAnimationKeyShow];
[self.layer removeAnimationForKey:UIViewVisibilityAnimationKeyHide];
if (!animated) {
self.alpha = 1.f;
self.hidden = !visible;
return;
}
self.hidden = NO;
CGFloat fromAlpha = visible ? 0.f : 1.f;
CGFloat toAlpha = visible ? 1.f : 0.f;
NSString *animationKey = visible ? UIViewVisibilityAnimationKeyShow : UIViewVisibilityAnimationKeyHide;
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
animation.duration = 0.25;
animation.fromValue = @(fromAlpha);
animation.toValue = @(toAlpha);
animation.delegate = self;
animation.removedOnCompletion = NO;
animation.fillMode = kCAFillModeForwards;
[self.layer addAnimation:animation forKey:animationKey];
}
#pragma mark - CAAnimationDelegate
- (void)animationDidStop:(CAAnimation *)animation finished:(BOOL)finished
{
if ([[self.layer animationForKey:UIViewVisibilityAnimationKeyHide] isEqual:animation]) {
self.hidden = YES;
}
}
@end