自动布局修改constriaint的乘法器 [英] auto layout modify multiplier of constriaint programmatically

问题描述

如何以编程方式修改约束的乘数？我设置以下：

How can I modify the multiplier of a constraint programmatically? I have set the following:

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:_button attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:0.5 constant:0.0]];

，我需要将其修改为：

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:_button attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];

推荐答案

像其他人说的，你必须删除旧的如果您不想将其存储为属性，只需设置标识符并搜索即可获取。

As others said,you have to delete the old one and add a new one.If you do not want to store it as a property,just set identifier and search to get it later

-(NSLayoutConstraint *)constraintWithIndientifer:(NSString *)identifer InView:(UIView *)view{
NSLayoutConstraint * constraintToFind = nil;
for (NSLayoutConstraint * constraint in view.constraints ) {
    if([constraint.identifier isEqualToString:identifer]){
        constraintToFind = constraint;
        break;
    }
}
return constraintToFind;
}

然后

  NSLayoutConstraint * constraint = [NSLayoutConstraint constraintWithItem:self.yellowView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeWidth multiplier:0.5 constant:0.0];
constraint.identifier = @"1234";
[self.view addConstraint:constraint];

然后你可以得到

    NSLayoutConstraint * constraint = [self constraintWithIndientifer:@"1234" InView:self.view];

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