ios - 使用自动布局设置此 UI

Question

我正在尝试使用自动布局设置一个 View ，以便在 View 改变大小时它可以很好地动画...

场景是...

我有一个 UIView 和一个名为 animView 的 subview 。 animView 在 View 框架之外开始。随着 View 的增长(变高)，animView 以相同的速率向下移动。当 animView 距 View 顶部 10 点(即 @"V:|-10-[animView]")时，它会停止并“固定”到该点。

即像这样的……

Answer 1

这个有效(Dropbox share for the project):

诀窍是使用不可见的 UIView 作为间隔对象。你称之为 animView 的 View 是这样设置的。因为我在 IB 中部分设置了它，它仍然会引发一些问题，但你会看到它按你想要的方式工作。

@implementation AnimView {

    UIView * _innerBox;
    UIView * _spacer;
}

然后从initWithCoder: 或initWithFrame: 调用方法- setUpEverything。

- (void) setUpEverything {


    // Because I set this up in IB with AutoLayout off, I think it 
    // still needs this. Won't work without it
    self.translatesAutoresizingMaskIntoConstraints = YES;

    // Otherwise you will see the box outside of animView
    self.clipsToBounds = YES;

    _innerBox = [[UIView alloc] init];
    _innerBox.backgroundColor = [UIColor blackColor];
    _spacer = [[UIView alloc] init];
    _spacer.backgroundColor = [UIColor clearColor]; 
    _innerBox.translatesAutoresizingMaskIntoConstraints = NO;
    _spacer.translatesAutoresizingMaskIntoConstraints = NO;
    [self addSubview:_innerBox];
    [self addSubview:_spacer];

    // Give _innerBox and _spacer some dimensions to prevent ambiguity

    NSLayoutConstraint *i02 = [NSLayoutConstraint constraintWithItem:_innerBox attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1.0f constant:50.0f];
    NSLayoutConstraint *i03 = [NSLayoutConstraint constraintWithItem:_innerBox attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1.0f constant:50.0f];
    NSLayoutConstraint *s02 = [NSLayoutConstraint constraintWithItem:_spacer attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:0 multiplier:1.0f constant:50.0f];

    // Center both views
    NSLayoutConstraint *i05 = [NSLayoutConstraint constraintWithItem:_innerBox attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterX multiplier:1.0f constant:0.0f];
    NSLayoutConstraint *s04 = [NSLayoutConstraint constraintWithItem:_spacer attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterX multiplier:1.0f constant:0.0f];

    // Set the top of _innerBox 10.0 points from the top of the superview with a low priority
    NSLayoutConstraint *i01 = [NSLayoutConstraint constraintWithItem:_innerBox attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeTop multiplier:1.0f constant:10.0f];
    i01.priority = 250;

    // Pin the spacer to the bottom of _innerBox;
    NSLayoutConstraint *i04 = [NSLayoutConstraint constraintWithItem:_innerBox attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:_spacer attribute:NSLayoutAttributeTop multiplier:1.0f constant:0.0f];

    // Pin the spacer's bottom to the bottom of the superview
    NSLayoutConstraint *s01 = [NSLayoutConstraint constraintWithItem:_spacer attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeBottom multiplier:1.0f constant:0.0f];

    // Stretch the spacer out as needed
    NSLayoutConstraint *s03 = [NSLayoutConstraint constraintWithItem:_spacer attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationGreaterThanOrEqual toItem:nil attribute:0 multiplier:1.0f constant:80.0f];


    [self addConstraints:@[i01,i02,i03,i04,i05,s01,s02,s03,s04]];

}