在呈现 ViewController 时以编程方式添加自动布局约束

Question

我正在展示一个视图控制器，就像 iPad 上我的主视图控制器的弹出窗口一样，它工作正常。但目前我正在将其 prefferedContentSize 设置为适合屏幕，因此当我旋转大小时不会自动调整大小。我需要弹出视图与主视图控制器中心对齐，纵向和横向宽度为 97%，高度为 90%。所以我现在尝试在我的 popupViewController 上添加自动布局约束，但不确定如何。以下是我到目前为止尝试过的代码。这给了我一个“NSInternalInconsistencyException”错误

#import "ViewController.h"

@interface ViewController ()
{
    PopUpViewController *popUpController;

}
@end


- (IBAction)showPopUp:(UIButton *)sender {

    popUpController =  [[PopUpViewController alloc]initWithNibName:@"PopUpViewController" bundle:nil];

    popUpController.view.center = self.view.center;
    popUpController.view.layer.cornerRadius =  8.0f;
    popUpController.view.layer.masksToBounds = YES;
    popUpController.view.layer.borderWidth = 1.0f;
    popUpController.view.layer.borderColor = [UIColor blueColor].CGColor;


    popUpController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
    popUpController.modalPresentationStyle =  UIModalPresentationFormSheet;

//    CGPoint frameSize = CGPointMake([[UIScreen mainScreen] bounds].size.width*0.97f, [[UIScreen mainScreen] bounds].size.height*0.9f);
//    popUpController.preferredContentSize = CGSizeMake(frameSize.x, frameSize.y);
    [self addConstraint];
    [self.navigationController presentViewController:popUpController animated:YES completion:nil];


}


-(void)addConstraint
{
    // Width constraint, half of parent view width
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:popUpController.view.superview
                                                          attribute:NSLayoutAttributeWidth
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeWidth
                                                         multiplier:0.97
                                                           constant:0]];

    // Height constraint, half of parent view height
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:popUpController.view.superview
                                                          attribute:NSLayoutAttributeHeight
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeHeight
                                                         multiplier:0.9
                                                           constant:0]];

    // Center horizontally
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:popUpController.view.superview
                                                          attribute:NSLayoutAttributeCenterX
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeCenterX
                                                         multiplier:1.0
                                                           constant:0.0]];

    // Center vertically
    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:popUpController.view.superview
                                                          attribute:NSLayoutAttributeCenterY
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeCenterY
                                                         multiplier:1.0
                                                           constant:0.0]];
}

Answer 1

在您的故事板中，将您的约束链接到控制器属性。然后，更改您的约束值：self.myConstraint.constant = 0;。 此外，在更改约束值后，在视图上调用 layoutIfNeeded，在 UIAnimation 中执行此操作。

管理约束的最简单方法。