ios - 如何使用 NSLayoutConstraint 限制 UIButton 高度

Question

我有 UItoolbar，其中添加了两项 1. UITextView 和 2. UIButton。 UITextview 的属性是根据输入的文本自动增长。 在 UITextview 高度增长的同时，我想限制 UIButton 高度，即 UIButton 高度不应增加。

[_toolbar setItems:[NSArray arrayWithObjects:barButtonItemCommentText,barButtonItemSubmit,nil]];
submitBtn.translatesAutoresizingMaskIntoConstraints = NO;
textView.translatesAutoresizingMaskIntoConstraints = NO;
_toolbar.translatesAutoresizingMaskIntoConstraints = NO;

[_toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-8-[textView]-79-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(textView)]];

 [_toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-8-[textView]-8-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(textView)]];

[_toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[submitBtn]-8-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(submitBtn)]];


[_toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-8-[submitBtn]-8-|" options:NSLayoutFormatAlignAllBaseline metrics:nil views:NSDictionaryOfVariableBindings(submitBtn)]];

[_toolbar addConstraint:[NSLayoutConstraint constraintWithItem:submitBtn
                                                 attribute:NSLayoutAttributeWidth
                                                 relatedBy:NSLayoutRelationEqual
                                                    toItem:nil
                                                 attribute:NSLayoutAttributeNotAnAttribute 
                                                multiplier:1.0 
                                                  constant:60]];
[textView setContentCompressionResistancePriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisHorizontal];
[textView setContentCompressionResistancePriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];

[_toolbar setContentCompressionResistancePriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];


[_toolbar addConstraint:[NSLayoutConstraint constraintWithItem:_toolbar attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationLessThanOrEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:MaxToolbarHeight]];

供引用，请参阅随附的屏幕截图:

Answer 1

下面提到的约束使其在垂直方向上拉伸(stretch)，因为它要求始终距离顶部和底部 8 像素。

[_toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-8-[submitBtn]-8-|" options:NSLayoutFormatAlignAllBaseline metrics:nil views:NSDictionaryOfVariableBindings(submitBtn)]];

如果将其更改为恒定高度，则它不会垂直增长，在这种情况下始终为 24 的高度。

[_toolbar addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[submitBtn(24)]-8-|" options:NSLayoutFormatAlignAllBaseline metrics:nil views:NSDictionaryOfVariableBindings(submitBtn)]];