iPhone5故事板自動佈局

Question

我正在使用自動佈局編寫iOS應用程序。 我想在屏幕Y中心的下方30點放置一個按鈕。 如何爲此添加約束條件？

Answer 1

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    UIView *superView = self.view; 
    UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect]; 

    [button setTranslatesAutoresizingMaskIntoConstraints:NO]; 
    [button setTitle:@"Button" forState:UIControlStateNormal]; 
    [superView addSubview:button]; 

    // adding constraints to the button 
    NSLayoutConstraint *cn = [NSLayoutConstraint constraintWithItem:button 
          attribute:NSLayoutAttributeTop 
          relatedBy:NSLayoutRelationEqual 
           toItem:superView 
          attribute:NSLayoutAttributeCenterY 
          multiplier:1.0 
           constant:30];// adds 30 points from Screen Center Y 
    [superView addConstraint:cn]; 


    cn = [NSLayoutConstraint constraintWithItem:button 
             attribute:NSLayoutAttributeCenterX 
             relatedBy:NSLayoutRelationEqual 
             toItem:superView 
             attribute:NSLayoutAttributeCenterX 
            multiplier:1.0 
             constant:0.0];// places the button in middle of X axis 
    [superView addConstraint:cn]; 

}