ios - 如何使用自动布局将微调器居中？

Question

我在项目中使用此微调器:https://github.com/misterwell/MMMaterialDesignSpinner

如何使用自动布局将其添加到屏幕中央，以便设备旋转时仍停留在屏幕中央？

Answer 1

您可以以编程方式添加自动布局约束。您可以使用4个约束-中心x，中心y，宽度和高度:

[self.spinner setTranslatesAutoresizingMaskIntoConstraints:NO];

NSLayoutConstraint *centerXConstraint = [NSLayoutConstraint constraintWithItem:self.spinner attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1.0f constant:0.0f];
NSLayoutConstraint *centerYConstraint = [NSLayoutConstraint constraintWithItem:self.spinner attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterY multiplier:1.0f constant:0.0f];
NSLayoutConstraint *widthConstraint = [NSLayoutConstraint constraintWithItem:self.spinner attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:kSpinnerWidth];
NSLayoutConstraint *heightConstraint = [NSLayoutConstraint constraintWithItem:self.spinner attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0f constant:kSpinnerHeight];

[self.view addConstraints:@[ centerXConstraint, centerYConstraint, widthConstraint, heightConstraint]];