UIGestureRecognizer目标问题

Question

我对UIGestureRecognizer有个奇怪的问题

我创建了一个类，在该类中声明手势识别器，并将self作为目标

​

-(id)initWithTextView:(UITextView*)theTextView withDelegate:(id<WordSelectionDelegate>)theDelegate
{
    if (self = [super init])
    {
        delegate = theDelegate;
        textView = theTextView;
        // init long press gesture to detect pressing on text elements
        UILongPressGestureRecognizer *longPressGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPressFromSender:)];
        [textView addGestureRecognizer:longPressGesture];
    }
    return self;
}




But the trick is when i actually make a long press gesture i have next error:


  * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSConcreteMutableAttributedString handleLongPressFromSender:]: unrecognized selector sent to instance 0x76227b0'


Why does the messages to self goes to String???

Answer 1

顺便说一句，问题无疑是拥有handleLongPressFromSender实例方法的对象(即您正在使用initWithTextView初始化的对象)在调用UILongPressGestureRecognizer时超出了范围。您需要检查该对象的范围。

例如，假设这个类的名称是MyTextViewHandler，那么假设您为一些视图控制器设置了一个viewDidLoad，其内容如下：

- (void)viewDidLoad
{
    [super viewDidLoad];

    // do a bunch of initialization

    MyTextViewHandler *textViewDelegate = [[MyTextViewHandler alloc] initWithTextView:self.textview withDelegate:self];
}

如果您在ARC项目中这样做，您将得到您描述的崩溃(因为textViewDelegate对象是viewDidLoad的本地对象，在该方法的末尾将超出范围)。如果使此委托处理程序类成为视图控制器的实例变量(或属性)，则此问题就会消失。