今天继续看了下CircleLayout布局。
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| - (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)path
{
UICollectionViewLayoutAttributes* attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:path];
attributes.size = CGSizeMake(ITEM_SIZE, ITEM_SIZE);
attributes.center = CGPointMake(_center.x + _radius * cosf(2 * path.item * M_PI / _cellCount),
_center.y + _radius * sinf(2 * path.item * M_PI / _cellCount));
return attributes;
}
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用三角函数计算求得当前item在圆环上得位置。
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| - (UICollectionViewLayoutAttributes *)initialLayoutAttributesForInsertedItemAtIndexPath:(NSIndexPath *)itemIndexPath
{
UICollectionViewLayoutAttributes* attributes = [self layoutAttributesForItemAtIndexPath:itemIndexPath];
attributes.alpha = 0.0;
attributes.center = CGPointMake(_center.x, _center.y);
return attributes;
}
- (UICollectionViewLayoutAttributes *)finalLayoutAttributesForDeletedItemAtIndexPath:(NSIndexPath *)itemIndexPath
{
UICollectionViewLayoutAttributes* attributes = [self layoutAttributesForItemAtIndexPath:itemIndexPath];
attributes.alpha = 0.0;
attributes.center = CGPointMake(_center.x, _center.y);
attributes.transform3D = CATransform3DMakeScale(0.1, 0.1, 1.0);
return attributes;
}
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| - (void)performBatchUpdates:(void (^)(void))updates completion:(void (^)(BOOL finished))completion;该方法调用的时候会触发上边两个动画方法
注意，现在这两个动画方法已经改掉了api名称，由下边两个替代
- (UICollectionViewLayoutAttributes *)initialLayoutAttributesForAppearingItemAtIndexPath:(NSIndexPath *)itemIndexPath{
}
- (UICollectionViewLayoutAttributes *)finalLayoutAttributesForDisappearingItemAtIndexPath:(NSIndexPath *)itemIndexPath{
}
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原文链接 http://www.onevcat.com/2012/08/advanced-collection-view/