Objective c 按钮';s行动导致;无效选择器";撞车,为什么?
当按下我创建的按钮时,此代码导致“无效选择器”错误。Objective c 按钮';s行动导致;无效选择器";撞车,为什么?,objective-c,ios,cocoa-touch,uibutton,target-action,Objective C,Ios,Cocoa Touch,Uibutton,Target Action,当按下我创建的按钮时,此代码导致“无效选择器”错误。test函数从何处获取 Main.m mainScreen = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 768, 1024)]; [self.view addSubview:mainScreen]; TaskButtons *tB = [[TaskButtons alloc] init]; [mainScreen addSubview:[tB TaskStart]]; TaskButt
test
函数从何处获取
Main.m
mainScreen = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 768, 1024)];
[self.view addSubview:mainScreen];
TaskButtons *tB = [[TaskButtons alloc] init];
[mainScreen addSubview:[tB TaskStart]];
TaskButtons.m
- (UIButton*)TaskStart {
CGRect buttonFrame = CGRectMake(500, 206, 400, 35);
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
button.frame = buttonFrame;
[button setTitle:@"Task Button" forState:UIControlStateNormal];
button.backgroundColor = [UIColor clearColor];
button.titleLabel.textAlignment = UITextAlignmentLeft;
button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;
[button setTitleColor:[UIColor darkGrayColor] forState:UIControlStateNormal];
[button addTarget:self action:@selector(test) forControlEvents:UIControlEventTouchUpInside];
return button;
}
- (void)test{
NSLog(@"test line");
}
似乎没有调用
test
函数。将按钮的目标设置为self
是否意味着它应该在TaskButtons
类中查找名为test
的函数?问题在于ARC过早释放实例化对象。所以要解决这个问题,我需要保留更长的时间
Main.h
#import "TaskButtons.m"
@interface ViewController : UIViewController {
TaskButtons *tB;
}
@property (nonatomic, retain) TaskButtons *tB;
语法问题:)在代码中替换这些行 请包含无效选择器消息的文本。这将告诉您操作消息真正发送到哪个对象。我发现它试图在调用选择器之前过早释放我的实例化对象。如果我将TaskButtons.m导入Main.h和TaskButtons*tB;在界面中。然后通过@property(非原子,retain)TaskButtons*tB将其保留在属性中;我可以将实例化的类保留足够长的时间来调用选择器,而不会过早释放我的类。测试
是一种方法,而不是函数。这可能是次要的,但UIControl选择器的形式是@selector(method:)
,其中签名看起来像-(void)method:(id)sender
。忽略参数可能会导致意外行为。
[button addTarget:self action:@selector(test:) forControlEvents:UIControlEventTouchUpInside];
- (void)test:(id)sender{
NSLog(@"test line");
}