UITableViewCell的setSelected方法中的animateWithDuration无效

Question

我正在尝试一个简单的动画来选择/取消选择UITableViewCell，如下所示：

- (void)setSelected:(BOOL)selected animated:(BOOL)animated {

    [UIView animateWithDuration: 0.5 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{

        tabConstraint.constant = selected ? 40 : 20;

    } completion:nil];
}

动画块内的代码将被调用，但它不是动画。一切都很好，但根本没有任何动画。我怎样才能让细胞选择动画？

Answer 1

每次更新autolayout约束时，都必须调用layoutIfNeeded，

- (void)setSelected:(BOOL)selected animated:(BOOL)animated {


    [UIView animateWithDuration: 0.5 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{

        tabConstraint.constant = selected ? 40 : 20;
        [self layoutIfNeeded];

    } completion:nil];
}

Answer 2

您需要在layoutIfNeeded区块中致电animations。有关详细信息，请查看此问题的已接受答案：How do I animate constraint changes?

Answer 3

你需要在动画块中调用layoutIfNeeded()： - ）

- (void)setSelected:(BOOL)selected animated:(BOOL)animated {

    tabConstraint.constant = selected ? 40 : 20;
    [UIView animateWithDuration: 0.5 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
        whateverTabYouHaveHere.layoutIfNeeded()
    } completion:nil];
}