我目前正在研究新 UICollectionView 的一些演示项目。
大多数演示都会重写子类中的 layoutAttributesForItemAtIndexPath 。但在该示例之一中从未调用该方法。
从Apple文档中我知道我必须重写layoutAttributesForItemAtIndexPath
我不知道在什么情况下调用这个方法。
这个方法只是针对特殊情况吗？
最佳答案
也许你可以在Apple文档中找到，子类必须重写layoutAttributesForElementsInRect和layoutAttributesForItemAtIndexPath 读这个:
layoutAttributesForElementsInRect:
Returns the layout attributes for all of the cells and views in the specified rectangle.
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
Parameters
rect
The rectangle (specified in the collection view’s coordinate system) containing the target views.
Return Value
An array of UICollectionViewLayoutAttributes objects representing the layout information for the cells and views. The default implementation returns nil.
Discussion
Subclasses must override this method and use it to return layout information for all items whose view intersects the specified rectangle. Your implementation should return attributes for all visual elements, including cells, supplementary views, and decoration views.
When creating the layout attributes, always create an attributes object that represents the correct element type (cell, supplementary, or decoration). The collection view differentiates between attributes for each type and uses that information to make decisions about which views to create and how to manage them.
Availability
Available in iOS 6.0 and later.
Declared In
UICollectionViewLayout.h
关于ios6 - layoutAttributesForItemAtIndexPath - 何时调用？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13202207/