相关疑难解决方法(0)

我UIScrollView只允许水平滚动,我想知道用户滚动的方向(左,右).我做的是继承UIScrollView和覆盖touchesMoved方法:

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesMoved:touches withEvent:event];

    UITouch *touch = [touches anyObject];
    float now = [touch locationInView:self].x;
    float before = [touch previousLocationInView:self].x;
    NSLog(@"%f %f", before, now);
    if (now > before){
        right = NO;
        NSLog(@"LEFT");
    }
    else{
        right = YES;
        NSLog(@"RIGHT");

    }

}

但是当我移动时,这种方法有时根本不会被调用.你怎么看？