iphone - 即使使用 performSelectorOnMainThread 和 waitUntilDone :NO，UI 也会锁定

Question

在我的 viewController 中，我有一个每 20 秒触发一次并调用位置更新的计时器。然后，当位置更新时，我通过 performSelectorOnMainThread 调用一个方法。出于某种原因，即使我包含了 waitUntilDone:NO，我的用户界面在执行检查时仍保持锁定状态。有谁知道我如何改进它以使屏幕不会每 20 秒卡住一次？谢谢!

-(void)viewDidLoad {

    NSTimer* myTimer = [NSTimer scheduledTimerWithTimeInterval: 20.0 target: self 
    selector: @selector(callAfterSixtySecond:) userInfo: nil repeats: YES];

    //other code
}

-(void) callAfterSixtySecond:(NSTimer*) t {

    locationManagerProfile.delegate = self;
    locationManagerProfile.desiredAccuracy = kCLLocationAccuracyBest; 
    [locationManagerProfile startUpdatingLocation];  
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation 
*)newLocation fromLocation:(CLLocation *)oldLocation {

    CLLocation *currentLocation = newLocation;

    if (currentLocation != nil) {

        [self performSelectorOnMainThread:@selector(buttonUpdate) withObject:nil 
        waitUntilDone:NO];   
    }
}

最后，我的界面是用这个方法更新的:

-(void) buttonUpdate {

    [locationManagerProfile stopUpdatingLocation];
    NSString *userLatitude =[(PDCAppDelegate *)[UIApplication sharedApplication].delegate 
    getUserLatitude];
    NSString *userLongitude =[(PDCAppDelegate *)[UIApplication sharedApplication].delegate 
    getUserLongitude];

    NSString *placeLatitude = [[NSUserDefaults standardUserDefaults]
    stringForKey:@"savedLatitude"];

    NSString *placeLongitude = [[NSUserDefaults standardUserDefaults]
    stringForKey:@"savedLongitude"];

    NSString *distanceURL = [NSString stringWithFormat:@"http://www.website.com/page.php?
    lat1=%@&lon1=%@&lat2=%@&lon2=%@",userLatitude, userLongitude, placeLatitude, 
    placeLongitude];

    NSData *distanceURLResult = [NSData dataWithContentsOfURL:[NSURL 
    URLWithString:distanceURL]];

    NSString *distanceInFeet = [[NSString alloc] initWithData:distanceURLResult 
    encoding:NSUTF8StringEncoding];

    if ([distanceInFeet isEqualToString:@"1"]) {

        UIBarButtonItem *btnGo = [[UIBarButtonItem alloc] initWithTitle:@"Button A" 
        style:UIBarButtonItemStyleBordered target:self action:@selector(actionA)];
        self.navigationItem.rightBarButtonItem = btnGo;
        [self.navigationItem.rightBarButtonItem setTintColor:[UIColor 
        colorWithRed:44.0/255.0 green:160.0/255.0 blue:65.0/255.0 alpha:1.0]];  
        UIBarButtonItem *btnGoTwo = [[UIBarButtonItem alloc] initWithTitle:@"Button B" 
        style:UIBarButtonItemStyleBordered target:self action:@selector(actionB)];
        self.navigationItem.rightBarButtonItem = btnGoTwo; 
        self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:btnGo, 
        btnGoTwo, nil];
    }
    if ([distanceInFeet isEqualToString:@"0"]) {
        UIBarButtonItem *btnGo = [[UIBarButtonItem alloc] initWithTitle:@"Button C" 
        style:UIBarButtonItemStyleBordered target:self action:@selector(actionC)];
        self.navigationItem.rightBarButtonItem = btnGo;
        [self.navigationItem.rightBarButtonItem setTintColor:[UIColor 
        colorWithRed:44.0/255.0 green:160.0/255.0 blue:65.0/255.0 alpha:1.0]];        
        UIBarButtonItem *btnGoTwo = [[UIBarButtonItem alloc] initWithTitle:@"Button B" 
        style:UIBarButtonItemStyleBordered target:self action:@selector(actionB)];
        self.navigationItem.rightBarButtonItem = btnGoTwo;   
        self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:btnGo, 
        btnGoTwo, nil];
    }       
}

Answer 1

您似乎在主线程上使用 dataWithContentsOfURL: 从 URL 获取一些数据。

看起来它会导致卡住。

尝试将其移出，以便仅在您要在 UI 中显示的数据准备就绪时才调用主线程。