为什么UILabel没有显示？

Question

在我的appDelegate.m我有这段代码，但UILabel没有显示，只有UIImageView。

为什么？

notificationView = [[UIImageView alloc] initWithFrame: CGRectMake(154, 320, 140, 47)];
notificationView.image = [UIImage imageNamed:@"notification.png"];

NSString *message = [NSString stringWithString:@"New Videos"];

notificationLabel = [[UILabel alloc] initWithFrame: CGRectMake(165, 313, 140, 47)]; 
notificationLabel.font = [UIFont boldSystemFontOfSize:12];
notificationLabel.textAlignment = UITextAlignmentLeft;
notificationLabel.text = [NSString stringWithFormat:@"%d %@", numberOfVideos, message];
notificationLabel.textColor = [UIColor whiteColor];
notificationLabel.backgroundColor = [UIColor clearColor];

notificationView.alpha = 0.0;
notificationLabel.alpha = 0.0;

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:1.5];
notificationView.alpha = 1.0;
notificationLabel.alpha = 1.0;
[UIView commitAnimations];

[self.window addSubview: notificationView];
[self.notificationView addSubview: notificationLabel];

[UIView commitAnimations];  

[notificationView release];
[notificationLabel release];

Answer 1

notificationLabel是notificationView的子视图。 它被置于超级视图范围之外。

尝试

notificationLabel = [[UILabel alloc] initWithFrame: CGRectMake(0, 0, 140, 47)]; 

从那里开始。对于所有子视图，超级视图的左上角是（0,0）。

Answer 2

通知视图的宽度为140。您的标签位于通知视图中的165的X位置，该位置超出了通知视图的范围。所以它不可见。