为什么在拖动视图时touchesMoved方法不会被多次调用--IOS

   pangstr = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];

- (void)handlePan:(UIPanGestureRecognizer *)recognizer{

    CGPoint translation = [recognizer translationInView:baseView];
    recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y);
    [recognizer setTranslation:CGPointMake(0, 0) inView:baseView];


    if (recognizer.state == UIGestureRecognizerStateEnded) {


        CGPoint velocity = [recognizer velocityInView:baseView];
        CGFloat magnitude = sqrtf((velocity.x * velocity.x));
        CGFloat slideMult = magnitude / 1000;
        NSLog(@"magnitude: %f, slideMult: %f", magnitude, slideMult);
        float slideFactor = 0.15 * slideMult;

        CGPoint finalPoint = CGPointMake(recognizer.view.center.x + (velocity.x * slideFactor),
                                         recognizer.view.center.y + (velocity.y * slideFactor));
}