Autolayout停止UITapGestureRecognizer？

Question

我设置了一个UIImageView来接受点击手势，点击按钮将隐藏起来，并在相同的位置显示一个UIActivityIndicatorView。逻辑很简单。但我有两个问题：

• 我需要添加[fb setTranslatesAutoresizingMaskIntoConstraints:NO];或[loading setTranslatesAutoresizingMaskIntoConstraints:NO];来避免约束冲突。为了安全起见，我加了两个。UIImageView和UIActivityIndicatorView似乎都有自己的内置约束： ""，""，"；8d68700.midX == + 18.5>"，“”。
• 我必须对[fb setTranslatesAutoresizingMaskIntoConstraints:NO];或[loading setTranslatesAutoresizingMaskIntoConstraints:NO];这一行进行评论。否则，UITapGestureRecognizer不再工作了，为什么？

代码：

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Do any additional setup after loading the view.

    // setup the loading activity indicator;
    loading = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
    [self.view addSubview:loading];
    loading.hidden = YES;

    // setup the fb button
    fb = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"facebook.png"]];
    fb.userInteractionEnabled = YES;

    UITapGestureRecognizer* tap = [[UITapGestureRecognizer alloc] init];
    [tap addTarget:self action:@selector(login:)];
    [fb addGestureRecognizer:tap];

    [self.view addSubview:fb];
    fb.hidden = YES;

    NSLayoutConstraint *c;
    c = [NSLayoutConstraint constraintWithItem:fb
                                     attribute:NSLayoutAttributeCenterX
                                     relatedBy:NSLayoutRelationEqual
                                        toItem:self.view
                                     attribute:NSLayoutAttributeCenterX
                                    multiplier:1
                                      constant:0];
    [self.view addConstraint:c];
    c = [NSLayoutConstraint constraintWithItem:fb
                                     attribute:NSLayoutAttributeCenterY
                                     relatedBy:NSLayoutRelationEqual
                                        toItem:self.view
                                     attribute:NSLayoutAttributeCenterY
                                    multiplier:1
                                      constant:0];
    [self.view addConstraint:c];

    c = [NSLayoutConstraint constraintWithItem:loading
                                     attribute:NSLayoutAttributeCenterX
                                     relatedBy:NSLayoutRelationEqual
                                        toItem:self.view
                                     attribute:NSLayoutAttributeCenterX
                                    multiplier:1
                                      constant:0];
    [self.view addConstraint:c];
    c = [NSLayoutConstraint constraintWithItem:loading
                                     attribute:NSLayoutAttributeCenterY
                                     relatedBy:NSLayoutRelationEqual
                                        toItem:self.view
                                     attribute:NSLayoutAttributeCenterY
                                    multiplier:1
                                      constant:0];
    [self.view addConstraint:c];

    [fb setTranslatesAutoresizingMaskIntoConstraints:NO];
    [loading setTranslatesAutoresizingMaskIntoConstraints:NO];
    [self.view setTranslatesAutoresizingMaskIntoConstraints:NO];
}

Answer 1

您需要调用setTranslatesAutoresizingMaskIntoConstraints:NO，因为自动调整掩码被转换为与自动收费系统冲突的约束。您通常不能使用自动调整掩码约束将自动布局约束添加到视图中，否则将进入不兼容的约束。

在您的情况下，主要问题是无法确定这些问题的宽度和高度。您还需要添加宽度和高度约束。如果自动布局系统无法计算，则无法使用中心约束来确定布局。