UIButton以编程方式创建但未显示在视图上(addSubview被调用)

Question

有一个AppDelegate和一个MainViewController.在MainViewController将UIButton被创建,AppDelegate设置背景图片,并应表现出它MainViewController.这几乎是它,但我看不到UIButton.

为了对齐目的,我IBOutlet在IB中创建并连接了按钮.

MainViewController.h

@property (strong, nonatomic) IBOutlet UIButton *searchBtn;

MainViewController.m

@synthesize searchBtn;

AppDelegate.m

@synthesize mainVC;


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // ViewController > setup:
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.mainVC = [[MainViewController alloc] initWithNibName:@"MainViewController" bundle:nil];
    self.window.rootViewController = self.mainVC;
    self.window.backgroundColor = [UIColor whiteColor];

    // Buttons > Set background images:
    [self.mainVC.searchBtn setImage:[UIImage imageNamed:@"search.png"] forState:UIControlStateNormal];

    [self.mainVC.view addSubview:self.mainVC.searchBtn];

    [self.window makeKeyAndVisible];

    return YES;
}

Answer 1

首先,IBOutlet如果您以编程方式创建它,则不需要.

其次,您可能希望在viewDidLoad视图控制器中而不是在您的视图控制器中创建按钮AppDelegate.这是您的视图控制器的业务.

第三,alloc init如果你以编程方式创建它,你可能应该是你的按钮:

UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(...)];
[button setBackgroundImage:someImage];
[button addTarget:self action:@selector(something:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:button];

类似的东西.