iOS-滑动手势UIPanGestureRecognizer左右

- (void)panAction:(UIPanGestureRecognizer *)pan{

    _canLeft = YES;
    _canRight = YES;

    //点相对于上一个点的位置
    CGPoint moviePoint = [pan translationInView:pan.view];

    //点的速度(正负可判断滑动趋势)
    CGPoint velocity = [pan velocityInView:pan.view];

    //侧滑的范围
    CGFloat instance = kScreenWidth - 100;

    //禁止左划的情况(在最左边时)
    if (pan.view.left <= 0 && moviePoint.x <= 0) {
        _canLeft = NO;
    }

    //禁止右划得情况(在最右边时)
    if (pan.view.left >= instance && moviePoint.x >= 0) {
        _canRight = NO;
    }

    //页面可以滑动的条件
    if (_canRight && _canLeft && pan.view.left >= 0 && pan.view.left <= instance){

        //移动
        pan.view.center =

        CGPointMake(pan.view.center.x + moviePoint.x, pan.view.center.y);
    }

    //每次都需要复位
    [pan setTranslation:CGPointZero inView:pan.view];

    //松开手指时判断滑动趋势让其归位

    if (pan.state == UIGestureRecognizerStateEnded) {
        if (pan.view.left < 10) {
            pan.view.left = 0;
        } else if(pan.view.left > instance - 10){
            pan.view.left = instance;
        }
    }
}