当屏幕方向改变时，可以转换先前视图控制器上的视图吗？

我有一种情况viewControllerA pushes viewControllerB到导航堆栈上。当用户旋转屏幕和方向时viewControllerB改变，我想要一个subviewA of viewControllerA来转变和重新定位自己。这可能吗？

我试过发送一个指针subviewA to viewControllerB，但是我对其位置所做的任何事情都会被忽略（当viewControllerB当前在屏幕上）。

我也尝试过重新定位subviewA in viewDidAppear of viewControllerA after viewControllerB从堆栈中弹出，但它看起来很难看，因为它在出现在屏幕上时会快速重新定位。还尝试在中操纵它viewWillAppear但什么也没发生。

我唯一能想到的就是发送viewControllerA的整个self.view to viewControllerB并将其附加为子视图viewControllerB旋转然后操纵它，然后将其移除。但这显然是一个可怕的解决方案。

有没有办法做到这一点？

可以通过以下方式进行约束：当超级视图的边界发生变化时，视图的位置和大小可以自动更改（不检查方向）。如果您以这种方式进行约束，那么无论旋转时视图是否在屏幕上，视图都会在旋转时进行正确的排列。

约束的形式为y = m*x + b其中 y 和 x 是两个视图，m 是乘数，b 是常数。它需要做一些数学计算来找出 m 和 b 的值将为您提供所需的约束。我在 NSLayoutConstraint 上创建了一个类别，允许您直接指定纵向和横向所需的值。你可以像这样使用它，

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.view addConstraint:[NSLayoutConstraint widthConstraintForView:self.rectangle superview:self.view portraitValue:100 landscapeValue:200]];
    [self.view addConstraint:[NSLayoutConstraint heightConstraintForView:self.rectangle superview:self.view portraitValue:150 landscapeValue:80]];
    [self.view addConstraint:[NSLayoutConstraint topConstraintForView:self.rectangle viewAttribute:NSLayoutAttributeTop superview:self.view portraitValue:200 landscapeValue:10]];
    [self.view addConstraint:[NSLayoutConstraint leftConstraintForView:self.rectangle viewAttribute:NSLayoutAttributeLeft superview:self.view portraitValue:100 landscapeValue:100]];
}

如果您在 IB 中设置了任何将被这些约束替换的约束，则可以将它们标记为将在运行时删除的占位符。该类别看起来像这样，

+(NSLayoutConstraint *)heightConstraintForView:(UIView *)subview superview:(UIView *)superview portraitValue:(CGFloat)pValue landscapeValue:(CGFloat)lValue {
    CGFloat multiplier = (pValue - lValue)/(superview.bounds.size.height - superview.bounds.size.width);
    CGFloat constant = pValue - (superview.bounds.size.height * multiplier);
    NSLayoutConstraint *con = [NSLayoutConstraint constraintWithItem:subview attribute:NSLayoutAttributeHeight relatedBy:0 toItem:superview attribute:NSLayoutAttributeHeight multiplier:multiplier constant:constant];
    NSLog(@"height coeffs: %f   %f",multiplier,constant);
    return con;
}

+(NSLayoutConstraint *)widthConstraintForView:(UIView *)subview superview:(UIView *)superview portraitValue:(CGFloat)pValue landscapeValue:(CGFloat)lValue {
    CGFloat multiplier = (pValue - lValue)/(superview.bounds.size.width - superview.bounds.size.height);
    CGFloat constant = pValue - (superview.bounds.size.width * multiplier);
    NSLayoutConstraint *con = [NSLayoutConstraint constraintWithItem:subview attribute:NSLayoutAttributeWidth relatedBy:0 toItem:superview attribute:NSLayoutAttributeWidth multiplier:multiplier constant:constant];
    NSLog(@"width coeffs: %f   %f",multiplier,constant);
    return con;
}


+(NSLayoutConstraint *)leftConstraintForView:(UIView *)subview viewAttribute:(NSLayoutAttribute) att superview:(UIView *)superview portraitValue:(CGFloat)pValue landscapeValue:(CGFloat)lValue {
    CGFloat multiplier = (pValue - lValue)/(superview.bounds.size.width - superview.bounds.size.height);
    CGFloat constant = pValue - (superview.bounds.size.width * multiplier);
    NSLayoutConstraint *con = [NSLayoutConstraint constraintWithItem:subview attribute:att relatedBy:0 toItem:superview attribute:NSLayoutAttributeRight multiplier:multiplier constant:constant];
    NSLog(@"left coeffs: %f   %f",multiplier,constant);
    return con;
}


+(NSLayoutConstraint *)rightConstraintForView:(UIView *)subview viewAttribute:(NSLayoutAttribute) att superview:(UIView *)superview portraitValue:(CGFloat)pValue landscapeValue:(CGFloat)lValue {
    CGFloat multiplier = (superview.bounds.size.width - pValue - superview.bounds.size.height + lValue)/(superview.bounds.size.width - superview.bounds.size.height);
    CGFloat constant = superview.bounds.size.width - pValue - (superview.bounds.size.width * multiplier);
    NSLayoutConstraint *con = [NSLayoutConstraint constraintWithItem:subview attribute:att relatedBy:0 toItem:superview attribute:NSLayoutAttributeRight multiplier:multiplier constant:constant];
     NSLog(@"right coeffs: %f   %f",multiplier,constant);
    return con;
}

+(NSLayoutConstraint *)topConstraintForView:(UIView *)subview viewAttribute:(NSLayoutAttribute) att superview:(UIView *)superview portraitValue:(CGFloat)pValue landscapeValue:(CGFloat)lValue {
    CGFloat multiplier = (pValue - lValue)/(superview.bounds.size.height - superview.bounds.size.width);
    CGFloat constant = pValue - (superview.bounds.size.height * multiplier);
    NSLayoutConstraint *con = [NSLayoutConstraint constraintWithItem:subview attribute:att relatedBy:0 toItem:superview attribute:NSLayoutAttributeBottom multiplier:multiplier constant:constant];
     NSLog(@"top coeffs: %f   %f",multiplier,constant);
    return con;
}


+(NSLayoutConstraint *)bottomConstraintForView:(UIView *)subview viewAttribute:(NSLayoutAttribute) att superview:(UIView *)superview portraitValue:(CGFloat)pValue landscapeValue:(CGFloat)lValue {
    CGFloat multiplier = (superview.bounds.size.height - pValue - superview.bounds.size.width + lValue)/(superview.bounds.size.height - superview.bounds.size.width);
    CGFloat constant = superview.bounds.size.height - pValue - (superview.bounds.size.height * multiplier);
    NSLayoutConstraint *con = [NSLayoutConstraint constraintWithItem:subview attribute:att relatedBy:0 toItem:superview attribute:NSLayoutAttributeBottom multiplier:multiplier constant:constant];
     NSLog(@"bottom coeffs: %f   %f",multiplier,constant);
    return con;
}

我在这里发布了这个示例项目，http://jmp.sh/SYgejs6