iphone - 两个 View ，一个在纵向下方，横向并排使用布局约束

Question

假设我有两个 TextView 。在纵向模式下，我希望这些在另一个下面 &在横向模式下，我希望它们并排放置

是否可以使用自动布局在 Storyboard中使用布局约束来做到这一点？如果是，那么如何？如果没有，那么实现这一目标的其他更好的解决方案是什么。

ios6是我的目标版本

Answer 1

下面是您可以在代码中实现的方式。

基本上你需要:

a) 在 UIViewController 的 updateViewConstraints 中为给定方向配置适当的 NSLayoutConstraint。

b) 在界面旋转时调用[self.view setNeedsUpdateConstraints]。

下面是一个 ViewController 实现和一个带有辅助方法的 UIView 类别。

@interface ConstraintsViewController ()

@property (nonatomic, weak) IBOutlet UIView  *upperOrLeftView, *lowerOrRightView;

@end


@implementation ConstraintsViewController

-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
    [super willAnimateRotationToInterfaceOrientation:toInterfaceOrientation duration:duration];
    [self.view setNeedsUpdateConstraints];
}

-(void)updateViewConstraints {
    [super updateViewConstraints];

    [self.view removeConstraintsRelatingToItems:@[self.upperOrLeftView,self.lowerOrRightView]];

    if(UIInterfaceOrientationIsPortrait(self.interfaceOrientation)) {
        [self.view constrainSubview:self.upperOrLeftView usingEdgeInsets:UIEdgeInsetsMake(0, 0, -1, 0)];
        [self.view constrainSubview:self.lowerOrRightView usingEdgeInsets:UIEdgeInsetsMake(-1, 0, 0, 0)];
        [self.view constrainSubviewsTopToBottom:@[self.upperOrLeftView, self.lowerOrRightView]];
    }
    else {
        [self.view constrainSubview:self.upperOrLeftView usingEdgeInsets:UIEdgeInsetsMake(0, 0, 0, -1)];
        [self.view constrainSubview:self.lowerOrRightView usingEdgeInsets:UIEdgeInsetsMake(0, -1, 0, 0)];
        [self.view constrainSubviewsLeftToRight:@[self.upperOrLeftView, self.lowerOrRightView]];
    }
}

@end

放在UIView+Constraints.h中

@interface UIView (Constraints)

-(void)removeConstraintsRelatingToItems:(NSArray*)items;

-(void)constrainSubview:(UIView*)subview usingEdgeInsets:(UIEdgeInsets)insets;

-(void)constrainSubviewsLeftToRight:(NSArray*)subviews;

-(void)constrainSubviewsTopToBottom:(NSArray*)subviews;

@end

这是UIView+Constraints.m

@implementation UIView (Constraints)

-(void)removeConstraintsRelatingToItems:(NSArray *)items {
    for(NSLayoutConstraint *constraint in self.constraints) {
        if([items containsObject:constraint.firstItem] || [items containsObject:constraint.secondItem]) {
            [self removeConstraint:constraint];
        }
    }
}

/** Set up constraints to flow the subviews from top to bottom and with equal heights */
-(void)constrainSubviewsTopToBottom:(NSArray*)subviews {
    if(subviews.count > 1) {
        UIView *anchorView = subviews[0];
        for(int i = 1; i < subviews.count; i++) {
            UIView *view = subviews[i];
            NSLayoutConstraint *heightConstraint = [NSLayoutConstraint constraintWithItem:anchorView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:view attribute:NSLayoutAttributeHeight multiplier:1.0 constant:0.0];
            NSLayoutConstraint *edgesConstraint = [NSLayoutConstraint constraintWithItem:anchorView attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:view attribute:NSLayoutAttributeTop multiplier:1.0 constant:0.0];
            [self addConstraints:@[heightConstraint, edgesConstraint]];
            anchorView = view;
        }
    }
}

/** Set up constraints to flow the subviews from left to right and with equal widths */
-(void)constrainSubviewsLeftToRight:(NSArray*)subviews {
    if(subviews.count > 1) {
        UIView *anchorView = subviews[0];
        for(int i = 1; i < subviews.count; i++) {
            UIView *view = subviews[i];
            NSLayoutConstraint *widthConstraint = [NSLayoutConstraint constraintWithItem:anchorView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:view attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0];
            NSLayoutConstraint *edgesConstraint = [NSLayoutConstraint constraintWithItem:anchorView attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:view attribute:NSLayoutAttributeLeft multiplier:1.0 constant:0.0];
            [self addConstraints:@[widthConstraint, edgesConstraint]];
            anchorView = view;
        }
    }
}

/**
 Set up constraints to anchor the various edges of the subview to it's superview (this view) using the provided insets.
 Any inset set to < 0.0 means that edge is ignored;
 */
-(void)constrainSubview:(UIView*)subview usingEdgeInsets:(UIEdgeInsets)insets {
    if(insets.top >= 0.0) {
        [self addConstraint:[NSLayoutConstraint constraintWithItem:subview attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeTop multiplier:1.0 constant:insets.top]];
    }

    if(insets.right >= 0.0) {
        [self addConstraint:[NSLayoutConstraint constraintWithItem:subview attribute:NSLayoutAttributeRight relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeRight multiplier:1.0 constant:-insets.right]];
    }

    if(insets.bottom >= 0.0) {
        [self addConstraint:[NSLayoutConstraint constraintWithItem:subview attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeBottom multiplier:1.0 constant:-insets.bottom]];
    }

    if(insets.left >= 0.0) {
        [self addConstraint:[NSLayoutConstraint constraintWithItem:subview attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeLeft multiplier:1.0 constant:insets.left]];
    }
}

@end