我已经阅读了几个帖子(比如
https://stackoverflow.com/a/5340339/1084822和
https://stackoverflow.com/a/15582466/1084822),用动画来调整UIView的大小,我们不能为框架设置动画,我们必须使用bounds.size,bounds.origin和position的混合.
我有一个自定义布局的UICollectionView.删除单元格时,将刷新布局,并且每个单元格都通过prepareLayout和layoutAttributesForElementsInRect：方法获取其新帧.然后,调用finalizeCollectionViewUpdates方法(我们可以编辑动画),最后单元格移动并调整大小.
我通过细胞动画的试验和错误做了很多探索,这是我发现的：
默认情况下,> 3个动画设置为我的可见单元格,即position,bounds.origin和bounds.size
>当我更改这些动画的from / to值时,只会影响单元格的POSITION,而不会影响它的SIZE
详细结果
默认值
当我坚持使用动画的默认值并使用这些日志检查它们的值时,
- (void)finalizeCollectionViewUpdates {
for(UICollectionViewCell* cell in [self.collectionView visibleCells]) {
NSLog(@"cell: %@",cell);
for(NSString* key in cell.layer.animationKeys) {
CABasicAnimation* animation = (CABasicAnimation*)[cell.layer animationForKey:key];
NSLog(@"animation %@: from %@ to %@",key,animation.fromValue,animation.toValue);
}
}
}
我为缩小的单元格得到了这个(它的框架代表它的最终状态)：
cell: <PlayQueueSongCell: 0x7fbf1bc8ebe0; baseClass = UICollectionViewCell; frame = (53.3333 80; 480 480); opaque = NO; animations = { position=<CABasicAnimation: 0x7fbf1bf54e20>; bounds.origin=<CABasicAnimation: 0x7fbf1bf556b0>; bounds.size=<CABasicAnimation: 0x7fbf1bf557a0>; }; layer = <CALayer: 0x7fbf1bc8e9f0>>
animation position: from NSPoint: {666.66666666666674,0} to NSPoint: {0,0}
animation bounds.origin: from NSPoint: {0,0}
animation bounds.size: from NSSize: {160,160} to NSSize: {0,0}
这对于消费单元(它的框架代表其最终状态)：
cell: <PlayQueueSongCell: 0x7fbf1bd6cd00; baseClass = UICollectionViewCell; frame = (640 0; 640 640); opaque = NO; animations = { position=<CABasicAnimation: 0x7fbf1bf55b70>; bounds.origin=<CABasicAnimation: 0x7fbf1bf55e20>; bounds.size=<CABasicAnimation: 0x7fbf1bf55f10>; }; layer = <CALayer: 0x7fbf1bd73200>>
animation position: from NSPoint: {666.66666666666652,0}
animation bounds.size: from NSSize: {-160,-160} to NSSize: {0,0}
以慢动作查看结果：
没有bounds.size动画
- (void)finalizeCollectionViewUpdates {
for(UICollectionViewCell* cell in [self.collectionView visibleCells]) {
for(NSString* key in cell.layer.animationKeys) {
[cell.layer removeAnimationForKey:@"bounds.size"];
}
}
}
我可以看到只有细胞的位置受到影响… 
bounds.size动画从(0,0)到(1000,1000)
当我将bounds.size的值更改为(0,0) – > (1000,1000)这个代码块：
- (void)finalizeCollectionViewUpdates {
for(UICollectionViewCell* cell in [self.collectionView visibleCells]) {
for(NSString* key in cell.layer.animationKeys) {
[cell.layer removeAnimationForKey:@"bounds.size"];
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"bounds.size"];
[animation setFromValue:[NSValue valueWithCGSize:CGSizeZero]];
[animation setToValue:[NSValue valueWithCGSize:CGSizeMake(1000,1000)]];
[animation setDuration:0.3];
[cell.layer addAnimation:animation forKey:@"bounds.size"];
}
}
}
我仍然可以看到只有细胞的位置受到影响… 
题
由于单元格在动画开始之前获取其新帧并且bounds.size不会影响单元格的大小,因此我无法找到一种方法来平滑地更改其大小.
每个人都在谈论的bounds.size和frame.size之间的相关性是什么？如何设置单元格大小的动画？
解决方法
我找到的解决方案是首先删除bounds.size动画,因为它以不需要的方式移动单元格.然后,我创建一个transform.scale动画,该动画以一个模拟其先前大小的值开始,并以值1停止.
if([cell.layer animationForKey:@"bounds.size"]) {
[cell.layer removeAnimationForKey:@"bounds.size"];
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
animation.duration = 0.3;
if(CGSizeEqualToSize(cell.frame.size,self.itemSize)) { //shrinking cell
animation.fromValue = @1.333;
animation.toValue = @1;
} else { //expending cell
animation.fromValue = @0.75;
animation.toValue = @1;
}
[cell.layer addAnimation:animation forKey:@"transform.scale"];
}
