CLLocationManager 始终为 null -Delegate 实现是单例类（NSObject 的子类而不是 UIViewController 的子类）

Posted 2023-03-05

【中文标题】CLLocationManager 始终为 null -Delegate 实现是单例类（NSObject 的子类而不是 UIViewController 的子类）

【英文标题】：CLLocationManager is always null -Delegate implementation is a Singleton Class (Subclass of NSObject instead of Subclass of UIViewController)

【发布时间】：2012-01-20 14:55:59

【问题描述】：

是否可以将 CLLocationManager 委托方法放在作为 NSObject 的子类而不是 UIViewController 的 Singleton 类中？我想这样做，因为我想从 App Delegate 调用 Singleton 并在 UI 加载时开始获取坐标

我有一个 locationcontroller 类，其中有以下初始化代码

static locationController *sharedLocController = NULL;
+(locationController *) getSharedController
   
    if (sharedLocController !=nil)
    
        NSLog(@"locationController has already been created.....");
        return sharedLocController;
    
    @synchronized(self)
    
        if (sharedLocController == nil)
        
            sharedLocController = [[self alloc] init];

        
    
    return sharedLocController;

//==============================================================================
+(id)alloc


    @synchronized([locationController class])
    

        NSAssert(sharedLocController == nil, @"Attempted to allocate a second instance of a sharedLocMgr singleton.");
        sharedLocController = [super alloc];
        return sharedLocController;
    
    return nil;

//==============================================================================
-(id)init

    self = [super init];

    if(sharedLocController !=nil)
    

        if(!self.locMgr)
        
            [self initLocationManager];

        
    



    return sharedLocController;

//==============================================================================
-(void)initLocationManager



    self.locMgr = [[CLLocationManager alloc] init];

    self.locMgr.delegate = self;
    self.locMgr.distanceFilter = kCLDistanceFilterNone;
    self.locMgr.desiredAccuracy = kCLLocationAccuracyBest;
    [self.locMgr startUpdatingLocation];
    NSLog(@"location manager object %@", locMgr);

问题是 self.locMgr 对象始终为空。 谢谢

【参考方案1】：

摆脱你的 alloc 函数。这不是必需的，它返回 nil，这意味着这个 init 调用被一个 nil 指针调用：

sharedLocController = [[self alloc] init];

【参考方案2】：

是的，可以将它们放在NSObject 子类中，这可能是一个单例。我使用类似的东西：

@interface MyCLController : NSObject <CLLocationManagerDelegate> 
    CLLocationManager *locationManager;


...

@end

虽然它不是单例。