我创建了一个自定义UIView，我使用它来模式显示UIToolbar和UIPickerView。我试图让它变得非常可重用，所以我在代码中创建了所有UI，包括设置约束。
这是我用来设置视图以添加到另一个视图的方法体，然后将控件设置为从底部到视图的动画。
我的视图层次结构如下：
"Owner" view (view to which this view is added):<br>
|-->"Background" view (set to the full size of "Owner", but mainly used as a dimmed background)<br>
|-->"Container" view (view which holds the toolbar and picker)
|--> Toolbar
|--> Picker
这是我用来设置用户界面的代码：
- (void)prepareForView:(UIView *)view {
UIView *containerView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
[containerView setTranslatesAutoresizingMaskIntoConstraints:NO];
self.containerView = containerView;
UIPickerView *picker = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width, 162.0f)];
[picker setTranslatesAutoresizingMaskIntoConstraints:NO];
self.picker = picker;
UIToolbar *toolbar = [[UIToolbar alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width, 44.0f)];
[toolbar setTranslatesAutoresizingMaskIntoConstraints:NO];
UIBarButtonItem *done = ...;
UIBarButtonItem *flexSpace = ...;
UIBarButtonItem *cancel = ...;
toolbar.items = @[done, flexSpace, cancel];
[containerView addSubview:picker];
[containerView addSubview:toolbar];
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|[picker]|" options:NSLayoutFormatAlignAllBaseline metrics:nil views:NSDictionaryOfVariableBindings(picker)]];
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|[toolbar]|" options:NSLayoutFormatAlignAllBaseline metrics:nil views:NSDictionaryOfVariableBindings(toolbar)]];
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[toolbar(==44)][picker(==162)]|" options:NSLayoutFormatAlignAllLeading metrics:nil views:NSDictionaryOfVariableBindings(toolbar, picker)]];
[containerView layoutIfNeeded];
[self addSubview:containerView];
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|[containerView]|" options:NSLayoutFormatAlignAllBaseline metrics:nil views:NSDictionaryOfVariableBindings(containerView)]];
self.containerTop = [NSLayoutConstraint constraintWithItem:containerView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeTop multiplier:1.0f constant:self.frame.size.height];
[self addConstraint:self.containerTop];
[self layoutIfNeeded];
}
基本上，我希望containerView根据其内容（应该是静态的206分）来调整大小。然后，我在其超级视图的顶部和顶部之间设置了一个垂直空间约束（self）。后来，我动画更改，以便工具栏和选择器＆＃34;向上滑动＆＃34;在屏幕上。
这里是动画代码（错误始终在此之前触发）：
// Add the view as a subview
[view addSubview:self];
// Setup view for display (here's what triggers the message)
[self prepareForView:view];
// Animate into view
[UIView animateWithDuration:animated?0.4f:0.0f
animations:^{
self.alpha = 1.0f;
}
completion:^(BOOL finished) {
// Now, slide the container view in from the bottom of the screen
self.containerTop.constant = self.frame.size.height - self.containerView.frame.size.height;
[UIView animateWithDuration:animated?0.4f:0.0f
animations:^{
[self layoutIfNeeded];
}
completion:^(BOOL finished) {
if (postDisplay != nil) {
postDisplay();
}
}
];
}
];
目前正在测试的所有模拟器和设备上正确显示，但我讨厌有警告/错误，我担心这可能 NOT 在某些时候按需要工作。< / p>
以下是显示的实际错误消息（我非常确定每次都是完全相同的错误）：
Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSLayoutConstraint:0x170283430 V:|-(0)-[UIToolbar:0x137590850] (Names: '|':UIView:0x170382b10 )>",
"<NSLayoutConstraint:0x170283480 V:[UIToolbar:0x137590850(44)]>",
"<NSLayoutConstraint:0x174084ba0 V:[UIToolbar:0x137590850]-(0)-[UIPickerView:0x137586100]>",
"<NSLayoutConstraint:0x174081fe0 V:[UIPickerView:0x137586100(162)]>",
"<NSLayoutConstraint:0x17409bbc0 V:[UIPickerView:0x137586100]-(0)-| (Names: '|':UIView:0x170382b10 )>",
"<NSLayoutConstraint:0x174095b80 V:[UIView:0x170382b10(736)]>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x174084ba0 V:[UIToolbar:0x137590850]-(0)-[UIPickerView:0x137586100]>
我不明白所有的约束都是预期的，然后显示的UI就是我想要的。当我在调试器中使用po [self.containerView recursiveDescription]检查视图的布局时，我发现框架正是我认为它们应该是的。我哪里错了？
答案 0 :(得分：4)
＆＃34;容器＆＃34;视图似乎从下面一行的高度为736：
<NSLayoutConstraint:0x174095b80 V:[UIView:0x170382b10(736)]>
您已按如下方式列出了视图：
------ UIView的顶部-------（y = 0）
- 0空间 -
UIToolBar（y = 0到y = 44）
- 0空间 -
UIPickerView（y = 44到y = 206）***
- 0空间 -
------ UIView的底部-----（y = 736）
***这就是冲突所引发的地方。这距离UIView的底部不能有0个空间，所有其他约束都设置了它们的方式，或者UIView的高度不能与所有其他约束一样。
编辑：
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|[containerView]|" options:NSLayoutFormatAlignAllBaseline metrics:nil views:NSDictionaryOfVariableBindings(containerView)]];
当你使用＆＃34; |＆＃34;在约束的visualFormat中，这是父视图。在这一行中你要说父视图在[containerView]的顶部有0个空格，而在[containerView]的底部也有0个空格。这使得容器视图与父级视图的高度相同。
编辑＃2：
请看以下内容。我相信这与你想要完成的事情很接近。
[containerView addSubview:picker];
[containerView addSubview:toolbar];
[self addSubview:containerView];
// Height & Width for containerView
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:[NSString stringWithFormat:@"V:[containerView(%f)]", containerView.frame.size.height] options:nil metrics:nil views:@{@"containerView":containerView}]];
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:[NSString stringWithFormat:@"H:[containerView(%f)]", containerView.frame.size.width] options:nil metrics:nil views:@{@"containerView":containerView}]];
// Height & Width for picker
[picker addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:[NSString stringWithFormat:@"V:[picker(%f)]", picker.frame.size.height] options:nil metrics:nil views:@{@"picker":picker}]];
[picker addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:[NSString stringWithFormat:@"H:[picker(%f)]", picker.frame.size.width] options:nil metrics:nil views:@{@"picker":picker}]];
// Height & Width for toolbar
[toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:[NSString stringWithFormat:@"V:[toolbar(%f)]", toolbar.frame.size.height] options:nil metrics:nil views:@{@"toolbar":toolbar}]];
[toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:[NSString stringWithFormat:@"H:[toolbar(%f)]", toolbar.frame.size.width] options:nil metrics:nil views:@{@"toolbar":toolbar}]];
// Vertical Positioning of picker & toolbar in containerView
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[picker]" options:nil metrics:nil views:@{@"picker":picker}]];
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[toolbar]-0-|" options:nil metrics:nil views:@{@"toolbar":toolbar}]];
// Horizontal Positioning of picker & toolbar in containerView
[containerView addConstraint:[NSLayoutConstraint constraintWithItem:containerView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:picker attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0]];
[containerView addConstraint:[NSLayoutConstraint constraintWithItem:containerView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:toolbar attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0]];
// Center containerView (X/Y) in parent (self)
[self addConstraint:[NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:containerView attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0]];
[self addConstraint:[NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:containerView attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0.0]];
编辑＃3：使用＆＃39;观看＆＃39;和＆＃39;指标＆＃39;字典。
NSDictionary *views = @{@"containerView":containerView, @"picker":picker, @"toolbar":toolbar};
NSDictionary *metrics = @{@"hCV":containerView.frame.size.height,
@"wCV":containerView.frame.size.width,
@"hP":picker.frame.size.height,
@"wP":picker.frame.size.width,
@"hT":toolbar.frame.size.height,
@"wT":toolbar.frame.size.width};
[containerView addSubview:picker];
[containerView addSubview:toolbar];
[self addSubview:containerView];
// Height & Width for containerView
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[containerView(hCV)]" options:0 metrics:metrics views:views]];
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[containerView(wCV)]" options:0 metrics:metrics views:views]];
// Height & Width for picker
[picker addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[picker(hP)]" options:0 metrics:metrics views:views]];
[picker addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[picker(wP)]" options:0 metrics:metrics views:views]];
// Height & Width for toolbar
[toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[toolbar(hT)]" options:0 metrics:metrics views:views]];
[toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[toolbar(wT)]" options:0 metrics:metrics views:views]];
// Vertical Positioning of picker & toolbar in containerView
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[picker]" options:0 metrics:nil views:views]];
[containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[toolbar]-0-|" options:0 metrics:nil views:views]];
// Horizontal Positioning of picker & toolbar in containerView
[containerView addConstraint:[NSLayoutConstraint constraintWithItem:containerView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:picker attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0]];
[containerView addConstraint:[NSLayoutConstraint constraintWithItem:containerView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:toolbar attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0]];
// Center containerView (X/Y) in parent (self)
[self addConstraint:[NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:containerView attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0]];
[self addConstraint:[NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:containerView attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0.0]];