ios - 设置 UIButton 目标

Question

我试图在按这种方式按下 buttonCancel 时调用一个方法:

+ (DejalActivityView *)activityViewForView:(UIView *)addToView withLabel:(NSString *)labelText width:(NSUInteger)aLabelWidth;
{
// Immediately remove any existing activity view:
if (dejalActivityView)
    [self removeView];

// Remember the new view (so this is a singleton):
dejalActivityView = [[self alloc] initForView:addToView withLabel:labelText width:aLabelWidth];

buttonCancel = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[buttonCancel addTarget:self
                 action:@selector(callCancelAlert:)
       forControlEvents:UIControlEventTouchDown];
[buttonCancel setTitle:@"Cancel upload" forState:UIControlStateNormal];
buttonCancel.frame = CGRectMake(250, 560, 300, 40);
[addToView addSubview:buttonCancel];
[buttonCancel setImage:[UIImage imageNamed:@"socialize-navbar-bg.png"] forState:UIControlStateNormal];

return dejalActivityView;
}

和方法

 -(IBAction)callCancelAlert:(id)sender{

UIAlertView *alert = [[UIAlertView alloc]
                      initWithTitle: @"Announcement"
                      message: @"It turns out that you are playing Addicus!"
                      delegate: nil
                      cancelButtonTitle:@"OK"
                      otherButtonTitles:nil];
[alert show];
//[alert release];
}

我收到这个错误:

'NSInvalidArgumentException'，原因:'+[DejalBezelActivityView callCancelAlert:]: 无法识别的选择器发送到类 0x3184e4' * 首先抛出调用栈: (0x327862a3 0x3a61f97f 0x32789ca3 0x32788531 0x326dff68 0x346790c5 0x34679077 0x34679055 0x3467890b 0x3467859b 0x345a1523 0x 3458e801 0x3458e11b 0x362805a3 0x362801d3 0x3275b173 0x3275b117 0x32759f99 0x326ccebd 0x326ccd49 0x3627f2eb 0x345e2301 0x39445 0x3aa56b20) libc++abi.dylib:终止调用抛出异常

应用程序崩溃了。

Answer 1

您的第一个方法是类方法 (+) 而不是实例方法 (-)，因此您处于类上下文中。

当你写作时

[buttonCancel addTarget:self
                 action:@selector(callCancelAlert:)
       forControlEvents:UIControlEventTouchDown];

self 不是指向一个类实例(例如，通过消息创建、分配和初始化消息)而是指向类本身。

因为在相同的方法中您分配了 DejalActivityView 的实例，所以您应该这样做:

[buttonCancel addTarget:dejalActivityView
                 action:@selector(callCancelAlert:)
       forControlEvents:UIControlEventTouchDown];