ios - objective-C : animating height constraint change not working

Question

我有两个代码块，一个有效，第二个没有。首先添加一个 View ，将其高度限制为 0，然后在动画 block 中取消此约束，使其长大。完美运行。第二个应该重新激活 0 height constraint使其高度收缩回 0 然后将其删除，但它会立即被删除。这是代码:

self.pickupAddressViewModel.infoViewBlock = ^(MandatoryPickupView * _Nonnull pickupView) {
        if (weakSelf.mandatoryPickupView) {
            return;
        }
        weakSelf.mandatoryPickupView = pickupView;
        [weakSelf.view addSubview:pickupView];

        CGFloat gap = weakSelf.orderButton.originY;
        [[pickupView.bottomAnchor constraintEqualToAnchor:weakSelf.view.bottomAnchor constant:-gap] setActive:YES];
        [[pickupView.leadingAnchor constraintEqualToAnchor:weakSelf.view.leadingAnchor
                                                  constant:16.0] setActive:YES];
        [[pickupView.trailingAnchor constraintEqualToAnchor:weakSelf.view.trailingAnchor
                                                   constant:-16.0] setActive:YES];
        weakSelf.mandatoryPickupViewHeight = [pickupView.heightAnchor constraintEqualToConstant:0];
        [weakSelf.mandatoryPickupViewHeight setActive:YES];

        [weakSelf.view layoutIfNeeded];
        [UIView animateWithDuration:0.5 animations:^{
            [weakSelf.mandatoryPickupViewHeight setActive:NO];
            [weakSelf.view layoutIfNeeded];
        }];
    };
    self.pickupAddressViewModel.closeViewBlock = ^{
        if (!weakSelf.mandatoryPickupView) {
            return;
        }
        [weakSelf.view layoutIfNeeded];
        [UIView animateWithDuration:10.5
                         animations:^{
                             [weakSelf.mandatoryPickupViewHeight setActive:YES];
                             [weakSelf.view layoutIfNeeded];
                         } completion:^(BOOL finished) {
                             [weakSelf.mandatoryPickupView removeFromSuperview];
                             weakSelf.mandatoryPickupView = nil;
                             weakSelf.mandatoryPickupViewHeight = nil;
                         }];
    };

这一切都发生在主线程上。

我尝试将框架的高度设置为 0，但也没有用

weakSelf.mandatoryPickupViewHeight是一个强大的属性，当我第二次激活时它不是零。

有什么建议么？谢谢!

Answer 1

当您为动画使用自动布局时，您可以按以下方式进行操作:

确保完成自动布局:

self.view.layoutIfNeeded()

然后在动画 block 之前更改约束。例如:

someConstraint.constant = 0

然后在更改约束后，告诉自动布局约束已更改:

self.view.setNeedsLayout()

然后您只需调用 layoutIfNeeded() 添加一个动画 block :

UIView.animate(withDuration: 1, animations: {
    self.view.layoutIfNeeded()
})

请注意，您没有停用约束 - 它必须始终处于事件状态。

我想在你的代码中问题出在:

    [UIView animateWithDuration:0.5 animations:^{
        [weakSelf.mandatoryPickupViewHeight setActive:NO];
        [weakSelf.view layoutIfNeeded];
    }];

尝试将其更改为

    [weakSelf.mandatoryPickupViewHeight setActive:NO];
    [weakSelf.view setNeedsLayout];
    [UIView animateWithDuration:0.5 animations:^{
        [weakSelf.view layoutIfNeeded];
    }];

虽然你在做什么似乎有点模糊。如果约束被禁用，您确定自动布局有足够的约束来计算正确的高度吗？如果是，你确定mandatoryPickupViewHeight约束是不是和那些冲突？