Gesture - Rotation旋转

1。

@property (nonatomic, strong) UILabel *lbl;

@property CGFloat rotationAngleInRadians; //旋转的角度

- (void) handleRotations:(UIRotationGestureRecognizer *)paramSender{

    if (self.lbl == nil){

        return;

    }

   //label以中心为原点，进行的旋转  CG:Core Graphics

    self.lbl.transform = CGAffineTransformMakeRotation(self.rotationAngleInRadians + paramSender.rotation);

    if (paramSender.state ==UIGestureRecognizerStateEnded){

        self.rotationAngleInRadians += paramSender.rotation;

    }

}

- (void)initLabel {

    self.lbl = [[UILabel alloc] initWithFrame:CGRectZero];

    self.lbl.text = @"Hello, World!";

    self.lbl.font = [UIFont systemFontOfSize:16.0f];

    [self.lbl sizeToFit];

    self.lbl.center = self.view.center;

    [self.view addSubview:self.lbl];

}

-(void)addGesture {

    UIRotationGestureRecognizer rotationGesture = [[UIRotationGestureRecognizer alloc] initWithTarget:self 

                                               action:@selector(handleRotations:)];

    

    [self.view addGestureRecognizer:rotationGesture];

  

}