iOS:autolayout,多个label如何设置居中显示?

Question

刚学autolayout,关于这个问题,一直没搞清楚！疑惑一:多个view(label)如何设置居中显示?c[backviewaddConstraints:[NSLayoutConstraintconstraintsWithVisualFormat:@"H:|[lab_before][lab_middle][lab_after]|"options:0metrics:nilviews:NSDictionaryOfVariableBindings(lab_before,lab_middle,lab_after)]];枚举类型参数中:ctypedefNS_OPTIONS(NSUInteger,NSLayoutFormatOptions){NSLayoutFormatAlignAllLeft=(1

Answer 1

刚刚算是勉强自己解决了：方法比较笨，即用一个backview来包含3个label，然后计算3个label的宽度并赋值给外层的backview，最后把backview居中显示，就完成了3个label的居中显示！如果有更好的方法，欢迎补充，讨论！
层次结构是:
c-view
-backview
-label1
-label2
-label3
c//设置水平布局
[backviewaddConstraints:[NSLayoutConstraintconstraintsWithVisualFormat:@"H:|[lab_before]-[lab_middle]-[lab_after]|"options:0metrics:nilviews:NSDictionaryOfVariableBindings(lab_before,lab_middle,lab_after)]];
c//设置backview宽度
[viewaddConstraint:[NSLayoutConstraintconstraintWithItem:backviewattribute:NSLayoutAttributeCenterXrelatedBy:NSLayoutRelationEqualtoItem:dynaContentViewattribute:NSLayoutAttributeCenterXmultiplier:1.0constant:before_width+middle_width+after_width]];
//设置backview居中显示
[viewaddConstraint:[NSLayoutConstraintconstraintWithItem:backviewattribute:NSLayoutAttributeCenterXrelatedBy:NSLayoutRelationEqualtoItem:dynaContentViewattribute:NSLayoutAttributeCenterXmultiplier:1.0constant:0.0]];
//设置backview的高度
[viewaddConstraints:[NSLayoutConstraintconstraintsWithVisualFormat:@"V:[backview(==34)]-0-|"options:0metrics:nilviews:NSDictionaryOfVariableBindings(backview)]];
问题来了:
有没有方法不计算每个label的宽度并赋值给superview的宽度,而是自动填充superview!
PS:我在测试的时候，发现不设置backview的宽度，就是整个屏幕的宽度！
2015/03/01更新:
c@interfaceCustomView1:UIView
@property(nonatomic,strong)UILabel*label1;
@property(nonatomic,strong)UILabel*label2;
@end
c@implementationCustomView1
-(id)init{
self=[superinit];
if(self){
_label1=[UILabelnew];
_label1.text=@"AAAAAA121212121";
_label1.textColor=[UIColorblackColor];
_label1.translatesAutoresizingMaskIntoConstraints=NO;
[selfaddSubview:_label1];
_label2=[UILabelnew];
_label2.text=@"BBBBBB";
_label2.textColor=[UIColororangeColor];
_label2.translatesAutoresizingMaskIntoConstraints=NO;
[selfaddSubview:_label2];
}
returnself;
}
-(void)updateConstraints{
NSDictionary*views=NSDictionaryOfVariableBindings(_label1,_label2);
//label1的宽高
[selfaddConstraint:[NSLayoutConstraintconstraintWithItem:_label1attribute:NSLayoutAttributeWidthrelatedBy:NSLayoutRelationEqualtoItem:nilattribute:NSLayoutAttributeNotAnAttributemultiplier:1.0constant:[_label1intrinsicContentSize].width]];
[selfaddConstraint:[NSLayoutConstraintconstraintWithItem:_label1attribute:NSLayoutAttributeHeightrelatedBy:NSLayoutRelationEqualtoItem:nilattribute:NSLayoutAttributeNotAnAttributemultiplier:1.0constant:[_label1intrinsicContentSize].height]];
//label2的宽高
[selfaddConstraint:[NSLayoutConstraintconstraintWithItem:_label2attribute:NSLayoutAttributeWidthrelatedBy:NSLayoutRelationEqualtoItem:nilattribute:NSLayoutAttributeNotAnAttributemultiplier:1.0constant:[_label2intrinsicContentSize].width]];
[selfaddConstraint:[NSLayoutConstraintconstraintWithItem:_label2attribute:NSLayoutAttributeHeightrelatedBy:NSLayoutRelationEqualtoItem:nilattribute:NSLayoutAttributeNotAnAttributemultiplier:1.0constant:[_label2intrinsicContentSize].height]];
[selfaddConstraints:[NSLayoutConstraintconstraintsWithVisualFormat:@"H:|[_label1][_label2]|"options:NSLayoutFormatAlignAllBottommetrics:nilviews:views]];
[selfaddConstraints:[NSLayoutConstraintconstraintsWithVisualFormat:@"V:[_label1]|"options:0metrics:nilviews:views]];
[superupdateConstraints];
}
-(CGSize)intrinsicContentSize{
CGSizel1size=[_label1intrinsicContentSize];
CGSizel2size=[_label2intrinsicContentSize];
returnCGSizeMake(l1size.width+l2size.width,l1size.height);
}
@end
                            

Answer 2

Q:有没有方法不计算每个label的宽度并赋值给superview的宽度,而是自动填充superview?
A:重写superview的updateConstraints和intrinsicContentSize方法