UIview演示仅在一个方向上旋转

Question

我正在使用此示例代码RotationPie。它是一个轮子，我想在一个方向上移动它或在我的项目中旋转它。我想提出不同的选项，用户将不得不选择其中一个。我希望车轮只能朝一个方向旋转。我认为我必须在类CDCircleGestureRecognizer中改变这个方法，但我不知道是什么。

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
   if ([self state] == UIGestureRecognizerStatePossible) {
      [self setState:UIGestureRecognizerStateBegan];
   } else {
      [self setState:UIGestureRecognizerStateChanged];
   }

   // We can look at any touch object since we know we 
   // have only 1. If there were more than 1 then 
   // touchesBegan:withEvent: would have failed the recognizer.
   UITouch *touch = [touches anyObject];

   // To rotate with one finger, we simulate a second finger.
   // The second figure is on the opposite side of the virtual
   // circle that represents the rotation gesture.

    CDCircle *view = (CDCircle *) [self view];
   CGPoint center = CGPointMake(CGRectGetMidX([view bounds]), CGRectGetMidY([view bounds]));
   CGPoint currentTouchPoint = [touch locationInView:view];
   CGPoint previousTouchPoint = [touch previousLocationInView:view];
    previousTouchDate = [NSDate date];
    CGFloat angleInRadians = atan2f(currentTouchPoint.y - center.y, currentTouchPoint.x - center.x) - atan2f(previousTouchPoint.y - center.y, previousTouchPoint.x - center.x);

    CGFloat one = atan2f(currentTouchPoint.y - center.y, currentTouchPoint.x - center.x); 

     CGFloat two =atan2f(previousTouchPoint.y - center.y, previousTouchPoint.x - center.x);    
    currentTransformAngle = atan2f(view.transform.b, view.transform.a);


   [self setRotation:angleInRadians];

Answer 1

我认为你应该将当前的angleInRadians存储在一个变量中，并且只有当新角度比当前角度更大（或更小）时才允许旋转。