UIPanGestureRecognizer

Configuring the Gesture Recognizer

@property(nonatomic) NSUInteger maximumNumberOfTouches//The maximum number of fingers that can be touching the view for this gesture to be recognized.
@property(nonatomic) NSUInteger minimumNumberOfTouches//The minimum number of fingers that can be touching the view for this gesture to be recognized.

Tracking the Location and Velocity of the Gesture

- (CGPoint)translationInView:(UIView *)view//The translation of the pan gesture in the coordinate system of the specified view.平移的距离。设置后速度为0.
- (void)setTranslation:(CGPoint)translation inView:(UIView *)view//设置平移的距离
- (CGPoint)velocityInView:(UIView *)view//速度。 which is expressed in points per second.

例子

方法1：

    CGFloat translationX = [pan translationInView:self.view].x;
    pan.view.center = CGPointMake(pan.view.center.x+translationX, pan.view.center.y);
    [pan setTranslation:CGPointZero inView:self.view];

方法2：

CGPoint translation = [recognizer translationInView:recognizer.view];

case UIGestureRecognizerStateBegan: {
            [recognizer setTranslation:CGPointMake(recognizer.view.frame.origin.x, 0) inView:recognizer.view];
            break;
        }
        case UIGestureRecognizerStateChanged: {
            [recognizer.view setTransform:CGAffineTransformMakeTranslation(MAX(0,translation.x), 0)];
            [self statusBarView].transform = recognizer.view.transform;
            break;
        }

目前看来，translationInView的参数是attach的view还是其父view关系不大。每次的translation都是与上次的叠加。因此如果每次设置为0，则累加坐标即可。否则要用setTransform。