问题描述

我有一个自定义流布局，当单元格从 CollectionView 插入和删除时，它使用以下两个函数调整它们的属性，但我无法弄清楚如何调整默认动画持续时间.

I have a custom flow layout which is adjusting the attributes for cells when they are being inserted and deleted from the CollectionView with the following two functions, but I'm unable to figure out how you would adjust the default animation duration.

- (UICollectionViewLayoutAttributes *)initialLayoutAttributesForAppearingItemAtIndexPath:(NSIndexPath *)itemIndexPath {
    UICollectionViewLayoutAttributes* attributes = [self layoutAttributesForItemAtIndexPath:itemIndexPath];

    // Assign the new layout attributes
    attributes.transform3D = CATransform3DMakeScale(0.5, 0.5, 0.5);
    attributes.alpha = 0;

    return attributes;
}

- (UICollectionViewLayoutAttributes *)finalLayoutAttributesForDisappearingItemAtIndexPath:(NSIndexPath *)itemIndexPath {

    UICollectionViewLayoutAttributes* attributes = [self layoutAttributesForItemAtIndexPath:itemIndexPath];

    // Assign the new layout attributes
    attributes.transform3D = CATransform3DMakeScale(0.5, 0.5, 0.5);
    attributes.alpha = 0;

    return attributes;
}

推荐答案

解决 gavrix 回答中提出的问题您可以使用新属性 CABasicAnimation *transformAnimation 子类化 UICollectionViewLayoutAttributes，然后创建具有合适持续时间的自定义转换并将其分配给 initialLayoutAttributesForAppearingItemAtIndexPath 中的属性，然后在 UICollectionViewCell 中根据需要应用属性:

To solve problem without hack that was proposed in the answer by gavrix you could subclass UICollectionViewLayoutAttributes with new property CABasicAnimation *transformAnimation, than create custom transformation with a suitable duration and assign it to attributes in initialLayoutAttributesForAppearingItemAtIndexPath, then in UICollectionViewCell apply the attributes as needed:

@interface AnimationCollectionViewLayoutAttributes : UICollectionViewLayoutAttributes
@property (nonatomic, strong)  CABasicAnimation *transformAnimation;
@end

@implementation AnimationCollectionViewLayoutAttributes
- (id)copyWithZone:(NSZone *)zone
{
    AnimationCollectionViewLayoutAttributes *attributes = [super copyWithZone:zone];
    attributes.transformAnimation = _transformAnimation;
    return attributes;
}

- (BOOL)isEqual:(id)other {
    if (other == self) {
        return YES;
    }
    if (!other || ![[other class] isEqual:[self class]]) {
        return NO;
    }
    if ([(( AnimationCollectionViewLayoutAttributes *) other) transformAnimation] != [self transformAnimation]) {
        return NO;
    }

    return YES;
}
@end

在布局类中

- (UICollectionViewLayoutAttributes *)initialLayoutAttributesForAppearingItemAtIndexPath:(NSIndexPath *)itemIndexPath {
    AnimationCollectionViewLayoutAttributes* attributes = (AnimationCollectionViewLayoutAttributes* )[super initialLayoutAttributesForAppearingItemAtIndexPath:itemIndexPath];

    CABasicAnimation *transformAnimation = [CABasicAnimation animationWithKeyPath:@"transform"];
    transformAnimation.duration = 1.0f;
    CGFloat height = [self collectionViewContentSize].height;

    transformAnimation.fromValue = [NSValue valueWithCATransform3D:CATransform3DMakeTranslation(0, 2*height, height)];
    transformAnimation.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeTranslation(0, attributes.bounds.origin.y, 0)];
    transformAnimation.removedOnCompletion = NO;
    transformAnimation.fillMode = kCAFillModeForwards;
    attributes.transformAnimation = transformAnimation;
    return attributes;
}

+ (Class)layoutAttributesClass { 
    return [AnimationCollectionViewLayoutAttributes class]; 
}

然后在 UICollectionViewCell 中应用属性

then in UICollectionViewCell apply the attributes

- (void) applyLayoutAttributes:(AnimationCollectionViewLayoutAttributes *)layoutAttributes
{
    [[self layer] addAnimation:layoutAttributes.transformAnimation forKey:@"transform"];
}

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