我有一系列以这种方式堆叠的视图
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| View 1 |
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| View 2 |
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| View 3 |
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这些视图可以展开和折叠，因此如果展开视图1，则视图2的顶部位于视图1的底部，而视图3的视图3则与视图2相关。
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| View 1 |
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|________________|
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| View 2 |
|________________|
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| View 3 |
|________________|
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| View 1 |
|________________|
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| View 2 |
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|________________|
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| View 3 |
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我不能通过IB添加这些视图，因为这个布局是以dinamycally方式创建的，所以我必须通过代码和约束来添加视图。
我正在做这个
UIView *previousView = nil;
for (UIView *view in views) {
if (previousView) {
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[previousView][view]"
options:0
metrics:nil
views:NSDictionaryOfVariableBindings(previousView, view)];
[superview addConstraints:constraints];
}
}
当我点按视图以展开它时，我收到错误
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)
(
"<NSAutoresizingMaskLayoutConstraint:0x76407b0 h=&-& v=--& V:[MyView:0x764c0f0(44)]>",
"<NSAutoresizingMaskLayoutConstraint:0x763e370 h=&-& v=--& V:[MyView:0x7646490(44)]>",
"<NSLayoutConstraint:0x76440d0 V:[MyView:0x764c0f0]-(0)-[MyView:0x7648eb0]>",
"<NSLayoutConstraint:0x7643920 V:[MyView:0x7648eb0]-(0)-[MyView:0x7646490]>",
"<NSAutoresizingMaskLayoutConstraint:0x76407f0 h=&-& v=--& MyView:0x764c0f0.midY == + 22>",
"<NSAutoresizingMaskLayoutConstraint:0x76d9ea0 h=&-& v=--& MyView:0x7648eb0.midY == + 91.5>",
"<NSAutoresizingMaskLayoutConstraint:0x763e3b0 h=&-& v=--& MyView:0x7646490.midY == + 110>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x7643920 V:[MyView:0x7648eb0]-(0)-[MyView:0x7646490]>
显然我做错了。我是否必须将setTranslatesAutoresizingMaskIntoConstraints设置为NO并将自己的约束添加到定位中？或者问题是我在该循环中添加的约束？
答案 0 :(得分：2)
您如何更改视图的大小？你有一个约束将你的两个视图之间的垂直空间固定为0.你得到的错误是否有任何其他约束（可能是你没有明确添加的那些）？我怀疑View 2和/或View 3可能存在另一个约束，它不允许它们向下移动以满足V-[View 1]-(0)-[View 2]约束。
如果不涉及其他限制，只需更改要展开或折叠的视图的高度即可。
正如Apple documentation中提到的，如果你自己设置所有约束，你应该调用setTranslatesAutoresizingMaskIntoConstraints:NO否则你的显式约束会与隐式添加的自动调整掩码约束发生冲突，这看起来像是在发生什么在这种情况下。
setTranslatesAutoresizingMaskIntoConstraints:NO并根据需要设置您需要的任何其他约束。
答案 1 :(得分：0)
使用自动布局时，如果要重新布局视图，则应更改约束而不是视图框架。
您可以参考此示例：
#define VIEW_COLLAPSED_HEIGHT 50
#define VIEW_EXPANDED_HEIGHT 100
@interface ViewController ()
@property (nonatomic, strong) NSLayoutConstraint *constraintHeight1;
@property (nonatomic, strong) NSLayoutConstraint *constraintHeight2;
@property (nonatomic, strong) NSLayoutConstraint *constraintHeight3;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
//Create 3 views
UIView *v1 = [[UIView alloc] init];
v1.translatesAutoresizingMaskIntoConstraints = NO;
v1.backgroundColor = [UIColor yellowColor];
[self.view addSubview:v1];
UIView *v2 = [[UIView alloc] init];
v2.translatesAutoresizingMaskIntoConstraints = NO;
v2.backgroundColor = [UIColor blueColor];
[self.view addSubview:v2];
UIView *v3 = [[UIView alloc] init];
v3.translatesAutoresizingMaskIntoConstraints = NO;
v3.backgroundColor = [UIColor greenColor];
[self.view addSubview:v3];
//Add constraints:
NSDictionary *variableBindings = NSDictionaryOfVariableBindings(v1, v2, v3);
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|-20-[v1]-20-|" options:0 metrics:nil views:variableBindings]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|-20-[v2]-20-|" options:0 metrics:nil views:variableBindings]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|-20-[v3]-20-|" options:0 metrics:nil views:variableBindings]];
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-60-[v1]" options:0 metrics:nil views:variableBindings]];
//Combine v1, v2, v3 vertically
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[v1]-0-[v2]-0-[v3]" options:0 metrics:nil views:variableBindings]];
//Define constraint for v1, v2, v3 height
self.constraintHeight1 = [NSLayoutConstraint constraintWithItem:v1 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:v1 attribute:NSLayoutAttributeHeight multiplier:0 constant:VIEW_COLLAPSED_HEIGHT];
[self.view addConstraint:self.constraintHeight1];
self.constraintHeight2 = [NSLayoutConstraint constraintWithItem:v2 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:v2 attribute:NSLayoutAttributeHeight multiplier:0 constant:VIEW_COLLAPSED_HEIGHT];
[self.view addConstraint:self.constraintHeight2];
self.constraintHeight3 = [NSLayoutConstraint constraintWithItem:v3 attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:v3 attribute:NSLayoutAttributeHeight multiplier:0 constant:VIEW_COLLAPSED_HEIGHT];
[self.view addConstraint:self.constraintHeight3];
}
@end
如果要展开/折叠视图，可以更改值constraint.constant：
- (IBAction)clickedBtnExpand:(id)sender {
[UIView animateWithDuration:0.5 animations:^{
self.constraintHeight1.constant = VIEW_EXPANDED_HEIGHT;
[self.view layoutIfNeeded];
}];
}
- (IBAction)clickedBtnCollapse:(id)sender {
[UIView animateWithDuration:0.5 animations:^{
self.constraintHeight1.constant = VIEW_COLLAPSED_HEIGHT;
[self.view layoutIfNeeded];
}];
}