关于UIButton titleLabel不显示 的问题

我创建了一个UIButton和titleLabel。UIbutton显示正常，titlelabel不显示。

UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 50, 50)];
[button setBackgroundImage:[UIImage imageNamed:@"button.png"] forState:UIControlStateNormal];
button.titleLabel.text = @"Title";
button.titleLabel.font = [UIFont fontWithName:@"System-Bold" size:25.0f];
[self.view addSubview:button];

我用的版本是IOS6+