需要有关以编程方式创建自动布局约束的帮助

Question

这是我第一次尝试以编程方式创建 auto layouts constraints，这是我的代码

- (void)viewDidLoad {
    [super viewDidLoad];

    UIView *view1 = [[UIView alloc]init];
    view1.backgroundColor = [UIColor lightGrayColor];
    [self.view addSubview:view1];
    [view1 setTranslatesAutoresizingMaskIntoConstraints:NO];

    NSDictionary *views = NSDictionaryOfVariableBindings(view1);

    NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"|-[view1]-|" options:NSLayoutFormatDirectionLeadingToTrailing metrics:nil views:views];

    NSArray *verticalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-[view1]-|" options:0 metrics:nil views:views];

    [view1 addConstraints:constraints];

    [view1 addConstraints:verticalConstraints];
}

这就是我在代码中尝试做的事情。

我遇到了这个巨大的错误

2015-12-16 12:13:59.254 test5b[1138:430691] The view hierarchy is not prepared for the constraint: When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled. Break on -[UIView(UIConstraintBasedLayout) _viewHierarchyUnpreparedForConstraint:] to debug. 2015-12-16 12:13:59.259 test5b[1138:430691] View hierarchy unprepared for constraint. Constraint: Container hierarchy: > View not found in container hierarchy: > That view's superview: ; layer = > 2015-12-16 12:13:59.260 test5b[1138:430691] * Terminating app due to uncaught exception 'NSGenericException', reason: 'Unable to install constraint on view. Does the constraint reference something from outside the subtree of the view? That's illegal. constraint: view:>' * First throw call stack: (0x1829f4f5c 0x1975e7f80 0x1829f4ea4 0x183890ef4 0x18804c620 0x18804c428 0x18804c2d0 0x18804c194 0x188056504 0x183890aa0 0x18805330c 0x188056420 0x1000d65f0 0x187f63a0c 0x187fd2fcc 0x187fd2f68 0x1881f494c 0x188200de4 0x1829ac48c 0x1829abdc4 0x1829a9d28 0x1828d8dc0 0x18da2c088 0x187fb2f60 0x1000d6ab8 0x197e128b8) libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

Answer 1

向 self.view 添加约束。替换以下内容：

[view1 addConstraints:constraints];
[view1 addConstraints:verticalConstraints];

与

[self.view addConstraints:constraints];
[self.view addConstraints:verticalConstraints];