Ios 当对象不可见时更改布局

我在屏幕上有4个对象：（UIView或UIButton）

在某些情况下，我需要隐藏其中一个或多个，这将导致：

A   C D 

或者这个：

A     D

在iOS 5中（不能使用

自动布局

）（除了使用大量的ifs并以编程方式设置位置之外）是否有办法修剪空间并强制上面的示例如下所示：

A C D
 A D

---

我使用KVO实现了这一点。
步骤1:注册

ViewController

作为所有视图中隐藏属性更改的观察者

[_view1 addObserver:self forKeyPath:@"hidden" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];
[_view2 addObserver:self forKeyPath:@"hidden" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];
[_view3 addObserver:self forKeyPath:@"hidden" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];
[_view4 addObserver:self forKeyPath:@"hidden" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:NULL];

步骤2:在

ViewController

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
  if(![object isEqual:[viewArray lastObject]]){
    UIView *viewToHide = (UIView *)object;
    CGRect newFrame = viewToHide.frame;
    CGRect oldFrame;
    int indexOfObject = [viewArray indexOfObject:object];
    for(int i = indexOfObject + 1; i < viewArray.count; i++){
      UIView *viewToChange = [viewArray objectAtIndex:i];
      if(viewToChange.hidden){
        continue;
      }
      else{
      oldFrame = viewToChange.frame;
      viewToChange.frame = newFrame;
      [viewArray replaceObjectAtIndex:i withObject:viewToChange];
      newFrame = oldFrame;
      }
    }
  }
}

---

我想没有简单的办法。您需要编写代码来更改帧或变换。幸运的是，我只有1-4个对象要显示。如果我需要显示和隐藏大约10个对象，该怎么办？这是很多ifs。使用键值观察（KVO）。当一个视图被隐藏时，您将得到消息，因此您可以改变其他视图。在那种情况下，你不需要太多的“如果”。

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
  if(![object isEqual:[viewArray lastObject]]){
    UIView *viewToHide = (UIView *)object;
    CGRect newFrame = viewToHide.frame;
    CGRect oldFrame;
    int indexOfObject = [viewArray indexOfObject:object];
    for(int i = indexOfObject + 1; i < viewArray.count; i++){
      UIView *viewToChange = [viewArray objectAtIndex:i];
      if(viewToChange.hidden){
        continue;
      }
      else{
      oldFrame = viewToChange.frame;
      viewToChange.frame = newFrame;
      [viewArray replaceObjectAtIndex:i withObject:viewToChange];
      newFrame = oldFrame;
      }
    }
  }
}

- (IBAction)viewTapped :(UIGestureRecognizer *)recogniser{
  CGPoint touchPoint = [recogniser locationInView:self.view];
  UIView *touchView = [self.view hitTest:touchPoint withEvent:nil];
  if([touchView isKindOfClass:[UIView class]]){
    touchView.hidden = YES;
  }
}