将图像添加到UINavigationBar中的UIButton

Question

我的应用程序中有一个导航栏，有两个按钮，每侧一个。此按钮用于更改应用程序的某些重要方面，如服务器和内容。

当服务器脱机或出现任何问题时，系统会要求用户更改此选项。

我想要的是：如何将图像附加到按钮以引起用户的注意？像这样：

但问题是：我甚至不知道如何开始寻找这个，我该怎么做？

Answer 1

我建议添加UILabel作为按钮的子视图而不是图像，这样您就可以通过在应用程序的任何位置使用NSNotificationCenter以编程方式更改它。

- (void)viewDidLoad
{
    [[NSNotificationCenter defaultCenter]
     addObserver:self
     selector:@selector(updateButtonLabel:)
     name:@"UpdateButtonLabel" object:nil];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem]
    button.frame = CGRectMake(0, 0, 35, 35);
    [button addTarget:self action:@selector(buttonMethods:) forControlEvents:UIControlEventTouchUpInside];
    [button setTintColor:[UIColor companyBlue]];
    [button setTitle:@"Button" forState:UIControlStateNormal];

    self.buttonLabel = [[UILabel alloc]initWithFrame:CGRectMake(18,-7,18,18)];
    self.buttonLabel.textColor = [UIColor whiteColor];
    self.buttonLabel.backgroundColor = [UIColor companyRed];
    self.buttonLabel.font = [UIFont systemFontOfSize:13.0];
    self.buttonLabel.layer.cornerRadius = 9;
    self.buttonLabel.layer.masksToBounds = YES;
    self.buttonLabel.textAlignment = NSTextAlignmentCenter;
    self.buttonLabel.text = @"!";

    [button addSubview:self.buttonLabel];
}

- (void)updateButtonLabel:(NSNotification *)notification
{
    NSString *labelString = notification.object;

   // Post a notification from any view controller with a string with no characters to hide the label:
    if (newString.length < 1)
    {
        self.buttonLabel.hidden = YES;
    }
    else
    {
        self.buttonLabel.text = labelString;
    }
}

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

Answer 2

对于此initWithCustomView，可以使用此功能，您可以在其中添加UIView个对象

 -(void)setRightBarButton{
        UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
        button.frame = CGRectMake(0, 0, 35, 35);
        [button addTarget:self action:@selector(buttonMethods:) forControlEvents:UIControlEventTouchUpInside];
        [button setTitle:@"Button" forState:UIControlStateNormal];
        self.navigationItem.rightBarButtonItem=[[UIBarButtonItem alloc]initWithCustomView:button];
    }