NSLayoutConstraint的简单应用
UIView *topView = [[UIView alloc] init]; topView.backgroundColor = [UIColor redColor]; [self.view addSubview:topView]; topView.translatesAutoresizingMaskIntoConstraints = NO; [self.view addConstraints:@[ [NSLayoutConstraint constraintWithItem:topView attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeft multiplier:1.0 constant:10], [NSLayoutConstraint constraintWithItem:topView attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeBottom multiplier:1.0 constant:-10], [NSLayoutConstraint constraintWithItem:topView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:100], [NSLayoutConstraint constraintWithItem:topView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:20] ]];
topView在父视图的左边间距10,下边间距-10,宽度为100,高度为20的实现代码