Question

我有一个按钮，按下按钮在时区之间循环并显示它们的时间;我不得不添加一个NSTimer，所以时间会在视图上更新。问题是当我按下按钮时，显示第二个时区时间，然后在一秒后消失，并被第一个时区替换。我认为这与NSTimer有关，因为当我评论它时，按钮工作正常，但时间不更新。任何帮助，将不胜感激。这是我的代码：

创建按钮

UIButton *changeZone = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
    changeZone.center = CGPointMake(250, 515);
    [changeZone addTarget:self action:@selector(changeZone:) forControlEvents:UIControlEventTouchUpInside];
    [changeZone setTitle:@"" forState:UIControlStateNormal];
    [self.view addSubview:changeZone];

设置基本TimeZone和NSTimer

[formatter setDateStyle:NSDateFormatterShortStyle];
    [formatter setDateFormat:@"hh:mm"];

    self.zoneName.text = (@"NYC");
    NSString *strSelectedDate= [formatter stringFromDate:date];
    self.zone.text = strSelectedDate;
    [NSTimer scheduledTimerWithTimeInterval:1.0
                                     target:self
                                   selector:@selector(updateTime:)
                                   userInfo:nil
                                    repeats:YES];

添加按钮操作并配置NSTimer

- (void)changeZone:(UIButton *) sender {

    if (_isTimeZone) {
        NSDate *date = [NSDate date];
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setDateStyle:NSDateFormatterShortStyle];
        [formatter setDateFormat:@"hh:mm"];
        [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"America/New_York"]];
        self.zoneName.text = (@"NYC");
        NSString *strSelectedDate = [formatter stringFromDate:date];
        self.zone.text = strSelectedDate;
        _isTimeZone = NO;
    } else {
        NSDate *date = [NSDate date];
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setDateStyle:NSDateFormatterShortStyle];
        [formatter setDateFormat:@"hh:mm"];
        [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"Europe/London"]];
        self.zoneName.text = (@"LON");

        NSString *strSelectedDate = [formatter stringFromDate:date];
        self.zone.text = strSelectedDate;
        _isTimeZone = YES;

    }
}

- (void)updateTime:(id)sender {
    dispatch_async(dispatch_get_main_queue(), ^{
    NSDate *date = [NSDate date];
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateStyle:NSDateFormatterShortStyle];
    [formatter setDateFormat:@"hh:mm"];
    NSString *strSelectedDate = [formatter stringFromDate:date];
    self.zone.text = strSelectedDate;
    });
}

Answer 1

您在计时器方法中创建的格式化程序，对您使用按钮设置的时区一无所知，因为您正在创建新的格式化程序。使用ivar而不是创建一个新的，只改变一个不同的东西，即时区。

@interface ViewController ()
@property (weak,nonatomic) IBOutlet UILabel *zone;
@property (weak,nonatomic) IBOutlet UILabel *zoneName;
@property (nonatomic) BOOL isTimeZone;
@end

@implementation ViewController {
    NSDateFormatter *formatter;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    UIButton *changeZone = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
    changeZone.center = CGPointMake(250, 515);
    [changeZone setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [self.view addSubview:changeZone];

    [changeZone addTarget:self action:@selector(changeZone:) forControlEvents:UIControlEventTouchUpInside];
    [changeZone setTitle:@"Change Zone" forState:UIControlStateNormal];

    formatter = [NSDateFormatter new];
    [formatter setDateStyle:NSDateFormatterShortStyle];
    [formatter setDateFormat:@"hh:mm"];

    NSDate *date = [NSDate date];
    self.zoneName.text = (@"NYC");
    NSString *strSelectedDate= [formatter stringFromDate:date];
    self.zone.text = strSelectedDate;
    [NSTimer scheduledTimerWithTimeInterval:1.0
                                     target:self
                                   selector:@selector(updateTime:)
                                   userInfo:nil
                                    repeats:YES];

    NSLog(@"%@",self.zoneName);

}

- (void)changeZone:(UIButton *) sender {

    if (_isTimeZone) {
        NSDate *date = [NSDate date];
        [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"America/New_York"]];
        self.zoneName.text = (@"NYC");
        NSString *strSelectedDate = [formatter stringFromDate:date];
        self.zone.text = strSelectedDate;
        _isTimeZone = NO;
    } else {
        NSDate *date = [NSDate date];
        [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"Europe/London"]];
        self.zoneName.text = (@"LON");

        NSString *strSelectedDate = [formatter stringFromDate:date];
        self.zone.text = strSelectedDate;
        _isTimeZone = YES;

    }
}


- (void)updateTime:(NSTimer *) timer {
        NSDate *date = [NSDate date];
        NSString *strSelectedDate = [formatter stringFromDate:date];
        self.zone.text = strSelectedDate;

}

为什么UIButton会继续恢复原状？

1 个答案: