Example[16070:269647] the behavior of the UICollectionViewFlowLayout is not defined because:

Example[16070:269647] the item width must be less than the width of the UICollectionView minus the section insets left and right values, minus the content insets left and right Example[16070:269647] The relevant UICollectionViewFlowLayout instance is , and it is attached to ; animations = { position=; bounds.origin=; bounds.size=; }; layer = ; contentOffset: {0, 0}; contentSize: {1024, 770}> collection view layout: .

Example[16070:269647] Make a symbolic breakpoint at UICollectionViewFlowLayoutBreakForInvalidSizes to catch this in the debugger.

UICollectionView报错如上
解决方法：

-(void)layoutSubviews {
   [super layoutSubviews];
    self.collectionView.bounds = CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height -20);
 }