如何以编程方式更新约束?

问题描述

我想以编程方式在代码中更新约束.我已将它们添加到情节提要控制器中.我为约束创建IBOutlet并将其连接.我在updateViewConstrains()中添加了值，但是它不起作用:

I want to update constraint programmatically in code. I have added them in storyboard controller. I make IBOutlet for the constraint and connect them. I add values in updateViewConstrains() but it isn't working:

func updateViewConstraints() {
    centerYConstraint.constant = 60

    super.updateViewConstraints()
}

推荐答案

在您的viewController.h文件中创建IBOutlet:

@property (weak, nonatomic) IBOutlet NSLayoutConstraint *nameButtonVerticalConstraint;

现在将其与相关的自动布局约束连接起来:

now connect it with the concerned autolayout constraint :

现在，您可以像这样简单地更改约束:

Now you can simply change the constraint like this :

self.nameButtonVerticalConstraint.constant=25;

如果想要更平滑的过渡，可以将其放在动画块中:

And if you want smoother transitions, you can put it inside an animation block :

[UIView animateWithDuration:1.2 delay:1 options:UIViewAnimationOptionCurveEaseInOut animations:^{
    self.nameButtonVerticalConstraint.constant=50;
    [self.view layoutIfNeeded];
} completion:nil];

以下摘录自此文章

如果由于上述约束的更新而其他约束将受到影响，则还必须调用以下约束:

If other constraints will be affected because of the update to the constraint above, the following must also be called:

[viewForUpdate setNeedsUpdateConstraints];

现在，通过在动画块内调用layoutIfNeeded为您的视图添加动画.

Now, animate yout view by calling layoutIfNeeded inside your animation block.

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