Question

确定代码现在正在运行，但它仍然需要工作。我得到的值是“粘性的”，它们不稳定（每次我尝试返回时，磁北似乎移动了一点），我需要稍微摇动设备以刷新/唤醒值..

Game.h

#import <Foundation/Foundation.h>

#import "CoreLocation.h"

@interface Game : NSObject

<CLLocationManagerDelegate>

@property BOOL stopButtonPressed;

-(void) play;

@end

Game.m

@implementation Game

- (id) init 
{
    self = [super init];

    self.stopButtonPressed = NO;

    CLLocationManager *locationManager;

    locationManager = [[CLLocationManager alloc] init];

    locationManager.delegate = self;

    return self;
}

-(void) play 
{

    [locationManager startUpdatingHeading]; 

    while(!self.stopButtonPressed)
    {
         double degrees = locationManager.heading.magneticHeading;

         int degreesRounded = (int)degrees;

         NSLog(@"Degrees : %i", degreesRounded);
    }
}

@end

MyViewController.m

@interface MyViewController()
{
    Game *game;
}
@end

@implementation MyViewController

-(void) viewDidLoad
{
    game = [[Game alloc] init];
}

- (IBAction)playPressed:(UIButton *)sender 
{
    [game performSelectorInBackground:@selector(play) withObject:nil];
}

- (IBAction)stopPressed:(UIButton *)sender 
{
    game.stopButtonPressed = YES;
}

@end

我做错了什么？

Answer 1

此代码将阻止该线程，如果它发生在主线程中，您将永远不会按下按钮。

CLLocationManager是一种异步机制。要正确使用它，您必须提供一个委托，当位置更新可用时它将通知（在大多数情况下，这可能是self（其中self是viewController或类似）。请参阅{{ 3}}

...
    CLLocationManager *locationManager;
    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate = self;
    [locationManager startUpdatingHeading];
}

- (void)locationManager:manager didUpdateHeading:newHeading {
    double degrees = newHeading.magneticHeading;
     NSLog(@"Degrees : %F", degrees);
}

Answer 2

您应该捕获CLLocationManager委托方法，而不是直接调用属性：https://developer.apple.com/library/mac/#documentation/CoreLocation/Reference/CLLocationManagerDelegate_Protocol/CLLocationManagerDelegate/CLLocationManagerDelegate.html#//apple_ref/occ/intf/CLLocationManagerDelegate

为什么我不能用这段代码读取设备与磁北的偏差？

2 个答案: