Question

我正在创建一个需要作为子视图添加到UIWindow的customalertview。我已经正确设置了它的子视图的约束，但是我很困惑何时/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％。高度已经与它的子视图有关。

- (void)show {
UIWindow *window = [[UIApplication sharedApplication] keyWindow];
[window addSubview:self];

[self addConstraint:[NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:[UIApplication sharedApplication].keyWindow attribute:NSLayoutAttributeWidth multiplier:0.7 constant:0]];         
[self addConstraint:[NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:_messageLabel attribute:NSLayoutAttributeBottom multiplier:1.0 constant:10]];
[self addConstraint:[NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:(_imageView.image ? _imageView : _titleLabel) attribute:NSLayoutAttributeTop multiplier:1.0 constant:-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.

Answer 1

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];

Answer 2

尝试更改constraintWithItem 自至 self.view

将子视图添加到UIWindow时自动执行

2 个答案: