我在哪里可以找到iPad示例代码[已关闭](Where can I find iPad Sample Code [closed])

 问题在于忘记静态实际上只是普通的C静态变量，它们可以在整个应用程序中全局访问。 （即，未封装在定义它们的范围内。） 
 
 同一个类的多个实例都在读取和写入同一个变量的值，从而导致不可预测的行为。 
 
 解决方案：传递实例级别消息以控制切换活动，您无法保证您的类是单例。 
 
 修改工作代码： 
 
- (void)beginAnimationWithOrgigin:(CGPoint)origin Terminus:(CGPoint)terminus Direction:(NSString*)direction{

    if (!direction)direction = @"FORWARD";

    NSLog (@"Message %@ in context %@",((UILabel*)_textLabel).text,_ctx);

    CGFloat text_width = ((UILabel*)_textLabel).frame.size.width;
    CGFloat display_width = self.frame.size.width;

    if ( text_width > display_width ) {
        float duration = (text_width - display_width)/40;
        [self setContentOffset:origin];

        [UIView beginAnimations:direction context:_ctx];
        [UIView setAnimationDelegate:self];
        [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];
        [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
        [UIView setAnimationDelay:1.0];
        [UIView setAnimationDuration:duration];
        [UIView setAnimationRepeatCount:1];
        [self setContentOffset:terminus];

        [UIView commitAnimations];

    }
}



- (void)animationDidStop:(NSString *)animationID
        finished:(NSNumber *)finished
         context:(void *)context
{

    NSLog(@"Animation Did stop context = %@",context);
    NSString *direction;
    CGPoint origin;
    CGPoint terminal_origin;

    if (![animationID isEqualToString:@"FORWARD"]){
        origin = CGPointMake(0, 0);
        terminal_origin = CGPointMake(((UILabel*)_textLabel).frame.size.width - self.frame.size.width, ((UILabel*)_textLabel).frame.origin.y);
        direction = @"FORWARD";
    }else{

        terminal_origin = CGPointMake(0, 0);
        origin = CGPointMake(((UILabel*)_textLabel).frame.size.width - self.frame.size.width, ((UILabel*)_textLabel).frame.origin.y);
        direction = @"BACKWARD";
        }

    [self beginAnimationWithOrgigin:origin Terminus:terminal_origin Direction:direction];
}

The problem was in forgetting that statics really are just ordinary C static variables which are globally accessible across the app. (i.e, not encapsulated in the scope that defined them.)
 
Multiple instances of the same class are all reading and writing values to a the same variable causing unpredictable behaviour. 
 
Solution: Pass instance level messages to control toggling activities where you can't guarantee your class is a singleton.
 
Modified Working Code:
 
- (void)beginAnimationWithOrgigin:(CGPoint)origin Terminus:(CGPoint)terminus Direction:(NSString*)direction{

    if (!direction)direction = @"FORWARD";

    NSLog (@"Message %@ in context %@",((UILabel*)_textLabel).text,_ctx);

    CGFloat text_width = ((UILabel*)_textLabel).frame.size.width;
    CGFloat display_width = self.frame.size.width;

    if ( text_width > display_width ) {
        float duration = (text_width - display_width)/40;
        [self setContentOffset:origin];

        [UIView beginAnimations:direction context:_ctx];
        [UIView setAnimationDelegate:self];
        [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)];
        [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
        [UIView setAnimationDelay:1.0];
        [UIView setAnimationDuration:duration];
        [UIView setAnimationRepeatCount:1];
        [self setContentOffset:terminus];

        [UIView commitAnimations];

    }
}



- (void)animationDidStop:(NSString *)animationID
        finished:(NSNumber *)finished
         context:(void *)context
{

    NSLog(@"Animation Did stop context = %@",context);
    NSString *direction;
    CGPoint origin;
    CGPoint terminal_origin;

    if (![animationID isEqualToString:@"FORWARD"]){
        origin = CGPointMake(0, 0);
        terminal_origin = CGPointMake(((UILabel*)_textLabel).frame.size.width - self.frame.size.width, ((UILabel*)_textLabel).frame.origin.y);
        direction = @"FORWARD";
    }else{

        terminal_origin = CGPointMake(0, 0);
        origin = CGPointMake(((UILabel*)_textLabel).frame.size.width - self.frame.size.width, ((UILabel*)_textLabel).frame.origin.y);
        direction = @"BACKWARD";
        }

    [self beginAnimationWithOrgigin:origin Terminus:terminal_origin Direction:direction];
}