如何隐藏/显示UIimageview？

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    CGRect viewRect = CGRectMake(250, 100, 30, 30);
    as = [[UIImageView alloc] initWithFrame:viewRect];
    as.backgroundColor=[UIColor clearColor];
    UIImage *img = [UIImage imageWithContentsOfFile: [[NSBundle mainBundle] pathForResource:@"check" ofType:@"png"]];
    [as setImage:img];
    [self.view addSubview:as];
    BOOL test= [[NSUserDefaults standardUserDefaults] boolForKey:@"switch"];
    NSLog(@"%@", (test ? @"YES" : @"NO"));
    if(test == YES)
        {
            as.hidden=NO;
        }
    else
        {
            as.hidden=YES;
        }
}

The test结果YES但是imageView不听命令.hidden或每次更新viewDidAppear如果不是，当我重新启动应用程序时，它会在我将其设置为“是”后消失，我会完美显示，但之后我永远不会去那里，我无法将其隐藏。 知道为什么它没有反应吗？

问题是你创建了新的UIImageView每次当你的视图出现时。你必须创建UIImageView正如一次：

- (void)loadView {
    [super loadView];
    CGRect viewRect = CGRectMake(250, 100, 30, 30);
    as = [[UIImageView alloc] initWithFrame:viewRect];
    as.backgroundColor = [UIColor clearColor];
    UIImage *img = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"check" ofType:@"png"]];
    as.image = img;
    [self.view addSubview:as];
    [as release];
}

然后显示/隐藏它 -viewDidAppear method:

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    BOOL test = [[NSUserDefaults standardUserDefaults] boolForKey:@"switch"];
    NSLog(@"%@", (test ? @"YES" : @"NO"));
    if(test == YES) {
        as.hidden = NO;
    }
    else {
        as.hidden = YES;
    }
}