如何使用UIGestureRecognizer子類實現輕掃

Question

如何實現UIGestureRecognizer子類的輕掃？

（如果你想知道爲什麼我想這樣做，而不是使用UISwipeGestureRecognizer這一點，是因爲我想刷卡識別添加到Chameleon的UIKit的端口）

Answer 1

我在它第一次去（還Github）：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { 
    UITouch *touch = [touches anyObject]; 
    _beganLocation = [touch locationInView:self.view]; 
} 

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { 
    UITouch *touch = [touches anyObject]; 
    CGPoint movedLocation = [touch locationInView:self.view]; 
    CGFloat distance = _distance(_beganLocation, movedLocation); 

    if (distance < SWIPE_MIN_DISTANCE) return; 

    CGFloat angle = _angle(_beganLocation, movedLocation); 
    int direction = -1; 
    if (angle > 270 - SWIPE_MAX_ANGLE && angle < 270 + SWIPE_MAX_ANGLE) { 
     direction = UISwipeGestureRecognizerDirectionUp; 
    } 
    if (angle > 180 - SWIPE_MAX_ANGLE && angle < 180 + SWIPE_MAX_ANGLE) { 
     direction = UISwipeGestureRecognizerDirectionLeft; 
    } 
    if (angle > 90 - SWIPE_MAX_ANGLE && angle < 90 + SWIPE_MAX_ANGLE) { 
     direction = UISwipeGestureRecognizerDirectionDown; 
    } 
    if ((angle > 360 - SWIPE_MAX_ANGLE && angle <= 360) || (angle >= 0 && angle <= SWIPE_MAX_ANGLE)) { 
     direction = UISwipeGestureRecognizerDirectionRight; 
    } 

    if (direction == -1) { 
     self.state = UIGestureRecognizerStateFailed; 
    } else { 
     self.state = self.direction == direction ? UIGestureRecognizerStateRecognized : UIGestureRecognizerStateFailed; 
    } 
} 

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { 
    self.state = UIGestureRecognizerStateFailed; 
} 

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { 
    self.state = UIGestureRecognizerStateFailed; 
} 

輔助功能：

static CGFloat _distance(CGPoint point1,CGPoint point2) 
{ 
    CGFloat dx = point2.x - point1.x; 
    CGFloat dy = point2.y - point1.y; 
    return sqrt(dx*dx + dy*dy); 
}; 

static CGFloat _angle(CGPoint start, CGPoint end) 
{ 
    CGPoint origin = CGPointMake(end.x - start.x, end.y - start.y); // get origin point to origin by subtracting end from start 
    CGFloat radians = atan2f(origin.y, origin.x); // get bearing in radians 
    CGFloat degrees = radians * (180.0/M_PI); // convert to degrees 
    degrees = (degrees > 0.0 ? degrees : (360.0 + degrees)); // correct discontinuity 
    return degrees; 
} 

應該注意的是，Chameleon的手勢識別器的實現是不完整的，並且包含最有可能特定於Twitterrific的邏輯。 Our fork包含進一步的修改。