ios - 选择文本字段时使 UICollectioView 滚动

Question

我有一个 UICollectionView。在其中一个项目的内部，我有 UITextField，问题是:当 keyboard 向上 textfield 被 隐藏时键盘 并且用户看不到他当前正在写的内容...

我试试下面的代码:

-(void)textFieldDidBeginEditing:(UITextField *)textField {

    UICollectionViewCell *cell;

    if (floor(NSFoundationVersionNumber) <= NSFoundationVersionNumber_iOS_6_1) {
        cell = (UICollectionViewCell *) textField.superview.superview;
    } else {
        cell = (UICollectionViewCell *) textField.superview.superview.superview;
    }

    [self.collectionView scrollToItemAtIndexPath:[self.collectionView indexPathForCell:cell] atScrollPosition:UICollectionViewScrollPositionTop animated:YES];

}

但应用程序崩溃并出现此错误:

2015-05-20 18:40:18.431 MyAPP[1154:111390] -[UICollectionView _layoutAttributes]: unrecognized selector sent to instance 0x1511a200
2015-05-20 18:40:18.432 MyAPP[1154:111390] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UICollectionView _layoutAttributes]: unrecognized selector sent to instance 0x1511a200'
*** First throw call stack:
(0x278b55a7 0x3549bc77 0x278baa6d 0x278b8949 0x277e9b68 0x2af7c3cd 0x122033 0x2aead5bd 0x2ae32279 0x2ae3257b 0x2aeac0b7 0x120b99 0x2afbdb39 0x2afbd843 0x2af37b61 0x2af37b61 0x2adaef67 0x2ade3ddd 0x2ade36ad 0x2adb9fbd 0x2b02dbb5 0x2adb8a07 0x2787c237 0x2787b64b 0x27879cc9 0x277c6b51 0x277c6963 0x2ed051a9 0x2ae18c91 0xa6fff 0x35a44aaf)
libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

也许在“superview.superview...”调用中找不到单元格对象？我会用这个:

UICollectionViewCell *cell;
UIView *superview = textField.superview;

while (superview) {
    if([superview isKindOfClass:[UICollectionViewCell class]]) {
        cell = (UICollectionViewCell *)superview;
        break;
    }
    superview = superview.superview;
}

if(cell == nil) {
    NSLog(@"Error...");
} else {
    [self.collectionView scrollToItemAtIndexPath:[_collectionView indexPathForCell:cell] atScrollPosition:UICollectionViewScrollPositionTop animated:YES];
}