iOS Objective-C全局悬浮按钮实现中loadView未调用的原因及解决方案

Hey there! Let's figure out why your ApplicationFloatingButtonController's loadView method isn't being called when you're trying to build a global floating button in iOS with Objective-C. Here's a breakdown of possible causes and actionable fixes:

• Your custom window isn't properly linked to its root view controller: If ApplicationFloatingButtonWindow doesn't have ApplicationFloatingButtonController set as its rootViewController, or the window isn't activated, the controller's lifecycle methods (including loadView) won't trigger at all.
• The window isn't added to the app's window hierarchy: In iOS, a window needs to be made visible (hidden = NO) and part of the app's active window stack for its associated view controller to initialize.
• No strong reference to the window: If your ApplicationFloatingButtonWindow instance is a local variable, ARC will automatically release it, so the controller never gets a chance to load.
• Typos or incorrect implementation in loadView: A misspelled method name (like LoadView with a capital L) or missing setup in the controller can also prevent the method from being called.

1. Properly Configure the Custom Window and Link the Controller #

Update your ApplicationFloatingButtonWindow.m to correctly initialize the controller, set it as the root, and configure the window to be visible:

@implementation ApplicationFloatingButtonWindow

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        // Set window level to ensure it sits above all other windows
        self.windowLevel = UIWindowLevelAlert + 1;
        // Make the window visible
        self.hidden = NO;
        
        // Initialize and attach the root view controller
        ApplicationFloatingButtonController *floatingBtnVC = [[ApplicationFloatingButtonController alloc] init];
        self.rootViewController = floatingBtnVC;
    }
    return self;
}

@end

2. Keep a Strong Global Reference to the Window #

To prevent the window from being released by ARC, hold onto it in your app's entry point:

For AppDelegate (pre-iOS 13): #

In AppDelegate.h:

@property (strong, nonatomic) ApplicationFloatingButtonWindow *floatingButtonWindow;

In AppDelegate.m:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Initialize the floating window with full screen bounds
    self.floatingButtonWindow = [[ApplicationFloatingButtonWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    return YES;
}

For SceneDelegate (iOS 13+): #

In SceneDelegate.h:

@property (strong, nonatomic) ApplicationFloatingButtonWindow *floatingButtonWindow;

In SceneDelegate.m:

- (void)scene:(UIScene *)scene willConnectToSession:(UISceneSession *)session options:(UISceneConnectionOptions *)connectionOptions {
    self.floatingButtonWindow = [[ApplicationFloatingButtonWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
}

3. Verify Your Controller's loadView Implementation #

Double-check that the method is correctly implemented in ApplicationFloatingButtonController.m—no typos, and proper view setup:

@implementation ApplicationFloatingButtonController

- (void)loadView {
    // Create the base view for the controller
    self.view = [[UIView alloc] initWithFrame:[UIScreen mainScreen].bounds];
    self.view.backgroundColor = [UIColor clearColor]; // Keep it transparent so it doesn't block underlying content
    
    // Add your floating button here
    UIButton *floatingBtn = [UIButton buttonWithType:UIButtonTypeCustom];
    floatingBtn.frame = CGRectMake(20, 200, 60, 60);
    floatingBtn.backgroundColor = [UIColor systemRedColor];
    [floatingBtn setTitle:@"Tap" forState:UIControlStateNormal];
    [self.view addSubview:floatingBtn];
}

@end

4. Debug with Logs (If Needed) #

If you're still stuck, add debug logs to your window's init method to confirm everything is configured correctly:

NSLog(@"Root VC attached: %@", self.rootViewController);
NSLog(@"Window hidden: %d", self.hidden);
NSLog(@"Window level: %f", self.windowLevel);

Ensure the root view controller isn't nil, hidden is NO, and the window level is higher than standard windows (UIWindowLevelNormal).

• On iOS 13+, make sure you're handling window setup in SceneDelegate instead of AppDelegate if your app uses the scene-based architecture.
• Be mindful of touch interactions—your floating window might block taps on underlying views, so you can override hitTest:withEvent: in ApplicationFloatingButtonWindow to pass through touches that aren't on the button.

内容的提问来源于stack exchange，提问作者Bocato