Objective c 向UIWindow添加子视图时的自动布局

我正在创建需要作为子视图添加到UIWindow的customalertview。我已经为它的子视图正确地设置了约束，但是我不知道何时/如何设置视图本身相对于窗口的约束

我希望alertview的宽度为屏幕宽度的70%。高度已与其子视图相关

-（无效）显示{
UIWindow*window=[[UIApplication sharedApplication]keyWindow]；
[窗口添加子视图：self]；
[self-addConstraint:[NSLayoutConstraint ConstraintWidth:self属性：NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:[UIApplication sharedApplication]。keyWindow属性：NSLayoutAttributeWidth乘数：0.7常量：0]；
[self-addConstraint:[NSLayoutConstraint constraintWithItem:self属性：NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual-toItem:_-messageLabel属性：NSLayoutAttributeBottom乘数：1.0常量：10]；
[self-addConstraint:[NSLayoutConstraint constraintWithItem:self属性：NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:（\u imageView.image？\u imageView:\u titleLabel）属性：NSLayoutAttributeTop乘数：1.0常量：-10]；
}

我做错了什么？我收到以下错误消息：

NSLayoutConstraint:0x181cd7c0 WFSoftAlertView:0x16e384c0.width == 0.7*UIWindow:0x16e7c8c0.width>
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.

---

尝试将您的constraintWithItem从 自己 到

---

self.view

尝试将您的constraintWithItem从

WFSoftAlertView.translatesAutoresizingMaskIntoConstraints=NO;
NSDictionary *views = NSDictionaryOfVariableBindings(WFSoftAlertView);
float width30 = self.view.frame.size.width*.3;
width30 = width30/2; // divided by 2 for padding of its left/rigth
NSString *str =[NSString stringWithFormat:@"%f",width30];
NSDictionary *metrics = @{@"width":str};

[self.view addSubview:WFSoftAlertView];
//add the WFSoftAlertView in center(x) of superview with a padding of "width"
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|-width-[WFSoftAlertView]-width-|" options:NSLayoutFormatAlignAllTop | NSLayoutFormatAlignAllBottom metrics:metrics views:views]]; 

// if you want center(y)
NSLayoutConstraint *centerY = [NSLayoutConstraint
                           constraintWithItem:WFSoftAlertView
                           attribute:NSLayoutAttributeCenterY
                           relatedBy:NSLayoutRelationEqual
                           toItem:self.view
                           attribute:NSLayoutAttributeCenterY
                           multiplier:1.0f
                           constant:0.f];

自己 到 自我观

WFSoftAlertView.translatesAutoresizingMaskIntoConstraints=NO;
NSDictionary *views = NSDictionaryOfVariableBindings(WFSoftAlertView);
float width30 = self.view.frame.size.width*.3;
width30 = width30/2; // divided by 2 for padding of its left/rigth
NSString *str =[NSString stringWithFormat:@"%f",width30];
NSDictionary *metrics = @{@"width":str};

[self.view addSubview:WFSoftAlertView];
//add the WFSoftAlertView in center(x) of superview with a padding of "width"
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|-width-[WFSoftAlertView]-width-|" options:NSLayoutFormatAlignAllTop | NSLayoutFormatAlignAllBottom metrics:metrics views:views]]; 

// if you want center(y)
NSLayoutConstraint *centerY = [NSLayoutConstraint
                           constraintWithItem:WFSoftAlertView
                           attribute:NSLayoutAttributeCenterY
                           relatedBy:NSLayoutRelationEqual
                           toItem:self.view
                           attribute:NSLayoutAttributeCenterY
                           multiplier:1.0f
                           constant:0.f];