我想创建一个具有自动布局按钮的 UIViewController。（与 WWDC 2012 会话 202 相同）此视图控制器被推送到 UINavigationController 中。
我根本不想使用故事板。一切都必须以编程方式完成。
问题是如何设置视图控制器主视图的尺寸，使其具有屏幕大小？
我的视图控制器如下所示：
@implementation EAViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.view.backgroundColor = [UIColor blueColor];
UIView * superview = self.view;
UIButton * button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setTitle:@"Button" forState:UIControlStateNormal];
[superview addSubview:button];
NSLayoutConstraint * cn = [NSLayoutConstraint constraintWithItem:button
attribute:NSLayoutAttributeCenterX
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeCenterX
multiplier:1.0
constant:0.0];
[self.view addConstraint: cn];
cn = [NSLayoutConstraint constraintWithItem:button
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:self.view
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:-20];
[self.view addConstraint:cn];
[self.view setTranslatesAutoresizingMaskIntoConstraints:NO];
[button setTranslatesAutoresizingMaskIntoConstraints:NO];
}
@end
我在 App Delegate 中像这样推送它
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// no story boards
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
EAViewController *viewController = [[EAViewController alloc] init];
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];
navigationController.view.backgroundColor = [UIColor whiteColor];
self.window.rootViewController = navigationController;
[self.window makeKeyAndVisible];
// Override point for customization after application launch.
return YES;
}
结果是按钮没有正确的 Y 偏移。如果我直接推送视图控制器而不使用导航控制器，它可以工作。