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[操作系统]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