iphone - 为什么 UIButton 标题不显示？

Question

在 UIViewController 的 viewDidLoad 方法中，我这样做：

UIButton *b = [[UIButton buttonWithType:UIButtonTypeRoundedRect] 
                                       initWithFrame:CGRectMake(0, 0, 100, 100)];

[b setTitle:@"Testing" forState:UIControlStateNormal];
[b setTitleColor: [UIColor blackColor] forState: UIControlStateNormal];
[self.view addSubview:b];                       // EDIT: should be 'b'
NSLog(@"button title: %@", [b titleLabel].text);

按钮显示，但标题不显示。NSLog 行将“Testing”打印到控制台。关于我做错了什么有什么建议吗？

Answer 1

我不能告诉你为什么它不起作用，但我确实有一个解决方案：

UIButton *b = [UIButton buttonWithType:UIButtonTypeRoundedRect] ;        
b. frame = CGRectMake(0, 0, 100, 100);

[b setTitle:@"Testing" forState:UIControlStateNormal];
[b setTitleColor: [UIColor blackColor] forState: UIControlStateNormal];
[self addSubview:b];   

将创建框架与按钮的分配和初始化分开。

Answer 2

问题在于

UIButton *b = [[UIButton buttonWithType:UIButtonTypeRoundedRect] 
                                       initWithFrame:CGRectMake(0, 0, 100, 100)];

buttonWithType返回一个自动释放的初始化对象。您不能再次向它发送一个 initWithFrame，因为一个对象只能被初始化一次。

单独设置它的框架：

b.frame = CGRectMake(0, 0, 100, 100);

Answer 3

改为这样做：

UIButton *b = [UIButton buttonWithType:UIButtonTypeRoundedRect];
b.frame = CGRectMake(0, 0, 100, 100);
[b setTitle:@"Testing" forState:UIControlStateNormal];
[b setTitleColor: [UIColor blackColor] forState: UIControlStateNormal];
[self.view addSubview:b];  

Answer 4

问题是你必须使用[[UIButton alloc] initWithFrame:]or [UIButton buttonWithType:]，你不应该同时使用两者。

Answer 5

您可以执行以下操作：

UIButton *b=[[UIButton alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];

b=[UIButton buttonWithType:UIButtonTypeRoundedRect];

[b setTitle:@"Button Title Here" forState:UIControlStateNormal];
[b setTitleColor:[UIColor blackColor] forState: UIControlStateNormal];
[self.view addSubview:b];

Answer 6

我遇到了同样的问题，结果是我设置的是图像而不是背景图像。当我这样做时，一切都很好：

[button setBackgroundImage:image forState:UIControlStateNormal];