我在UICollectionView中有一个基本的网格.这是一个简单的2列,使用UICollectionViewDelegateFlowLayout的多行布局.选择单元格后,我想对背景变暗,将单元格浮动到屏幕中心,然后根据所选单元格创建一个工作流程.我对UICollectionViews来说相当新鲜,我不知道最好的办法.
UICollectionView的自定义布局是否在选择单元格时有效？
或者有一种我可以为所选单元格动画而不必创建新布局的方式
如果有人能让我走正确的方向,我想我会很好的研究如何执行它.
解决方法
在尝试了几个(而且很奇怪的)解决方案之后,我通过编写自己的UICollectionView布局解决了这个问题.我尝试过的以前的解决方案
>在UICollectionView顶部添加一个自定义UIView,并尝试通过覆盖原始单元格进行移动,使背景变暗,并使新的UIView动画化
>在不创建全新布局的情况下动画化单元格
我试图避免它,但是在我编码之后,它比我原来想象的痛苦要少得多.
这是我的代码,任何有兴趣的人：
.H：
@interface FMStackedLayout : UICollectionViewLayout @property(nonatomic,assign) CGPoint center; @property(nonatomic,assign) NSInteger cellCount; -(id)initWithSelectedCellIndexPath:(NSIndexPath *)indexPath; @end
.M：
#define ITEM_WIDTH 128.0f
#define ITEM_HEIGHT 180.0f
static NSUInteger const RotationCount = 32;
static NSUInteger const RotationStride = 3;
static NSUInteger const PhotoCellBaseZIndex = 100;
@interface FMStackedLayout ()
@property(strong,nonatomic) NSArray *rotations;
@property(strong,nonatomic) NSIndexPath *selectedindexPath;
@end
@implementation FMStackedLayout
#pragma mark - Lifecycle
-(id)initWithSelectedCellIndexPath:(NSIndexPath *)indexPath{
self = [super init];
if (self) {
self.selectedindexPath = indexPath;
[self setup];
}
return self;
}
-(id)initWithCoder:(NSCoder *)aDecoder{
self = [super init];
if (self){
[self setup];
}
return self;
}
-(void)setup{
NSMutableArray *rotations = [NSMutableArray arrayWithCapacity:RotationCount];
CGFloat percentage = 0.0f;
for (NSUInteger i = 0; i < RotationCount; i++) {
// Ensure that each angle is different enough to be seen
CGFloat newPercentage = 0.0f;
do {
newPercentage = ((CGFloat)(arc4random() % 220) - 110) * 0.0001f;
} while (fabsf(percentage - newPercentage) < 0.006);
percentage = newPercentage;
CGFloat angle = 2 * M_PI * (1.0f + percentage);
CATransform3D transform = CATransform3DMakeRotation(angle,0.0f,1.0f);
[rotations addobject:[NSValue valueWithCATransform3D:transform]];
}
self.rotations = rotations;
}
#pragma mark - Layout
-(void)prepareLayout{
[super prepareLayout];
CGSize size = self.collectionView.frame.size;
self.cellCount = [self.collectionView numberOfItemsInSection:0];
self.center = CGPointMake(size.width / 2.0,size.height / 2.0);
}
-(CGSize)collectionViewContentSize{
return self.collectionView.frame.size;
}
-(UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath{
UICollectionViewLayoutAttributes *attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
attributes.size = CGSizeMake(ITEM_WIDTH,ITEM_HEIGHT);
attributes.center = self.center;
if (indexPath.item == self.selectedindexPath.item) {
attributes.zIndex = 100;
}else{
attributes.transform3D = [self transformForPersonViewAtIndex:indexPath];
}
return attributes;
}
-(NSArray *)layoutAttributesForElementsInRect:(CGRect)rect{
NSMutableArray *attributes = [NSMutableArray array];
for (NSInteger i = 0; i < self.cellCount; i++) {
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i
inSection:0];
[attributes addobject:[self layoutAttributesForItemAtIndexPath:indexPath]];
}
return attributes;
}
#pragma mark - Private
-(CATransform3D)transformForPersonViewAtIndex:(NSIndexPath *)indexPath{
NSInteger offset = (indexPath.section * RotationStride + indexPath.item);
return [self.rotations[offset % RotationCount] CATransform3DValue];
}
@end
然后,在你的UICollectionView上,你打电话
MyLayout *stackedLayout = [[MyLayout alloc] initWithSelectedCellIndexPath:indexPath];
[stackedLayout invalidateLayout];
[self.collectionView setCollectionViewLayout:stackedLayout
animated:YES];
单元格之间的动画将由自定义布局处理.