在iOS6上，下面这段代码可以把手势识别注册上，一切工作正常。可是到了iOS7下则不生效，有哪里做的不对吗？

@implementation YFJLeftSwipeDeleteTableView

- (id)initWithFrame:(CGRect)frame style:(UITableViewStyle)style
{
    self = [super initWithFrame:frame style:style];
    if (self) {
        _leftGestureRecognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swiped:)];
        _leftGestureRecognizer.direction = UISwipeGestureRecognizerDirectionLeft;
        _leftGestureRecognizer.delegate = self;
        [self addGestureRecognizer:_leftGestureRecognizer];

        _rightGestureRecognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swiped:)];
        _rightGestureRecognizer.delegate = self;
        _rightGestureRecognizer.direction = UISwipeGestureRecognizerDirectionRight;
        [self addGestureRecognizer:_rightGestureRecognizer];

        _tapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)];
        _tapGestureRecognizer.delegate = self;
        // Don't add this yet

        _deleteButton = [UIButton buttonWithType:UIButtonTypeCustom];
        _deleteButton.frame = CGRectMake(screenWidth(), 0, kDeleteButtonWidth, kDeleteButtonHeight);
        _deleteButton.backgroundColor = [UIColor redColor];
        _deleteButton.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin;
        [_deleteButton setTitle:@"XXXX" forState:UIControlStateNormal];
        [_deleteButton addTarget:self action:@selector(deleteItem:) forControlEvents:UIControlEventTouchUpInside];
        [self addSubview:_deleteButton];

        [self setAutoresizingMask:UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth];
    }
    return self;
}