转载自Creating a Custom Rotation Gesture Recognizer for iOS Apps

创建自定义的旋转手势

主要重写了4个方法：

- (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event- (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event- (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event- (void)touchesCancelled:(NSSet*)touches withEvent:(UIEvent*)event

主要代码如下，原理见注释：

@protocol CAYSwirlGestureRecognizerDelegate <UIGestureRecognizerDelegate>@end@interface CAYSwirlGestureRecognizer : UIGestureRecognizer@property CGFloat currentAngle;@property CGFloat previousAngle;@end#import "CAYSwirlGestureRecognizer.h"@interface CAYSwirlGestureRecognizer ()@property (strong, nonatomic) id target;@property (nonatomic) SEL action;@end@implementation CAYSwirlGestureRecognizer- (id)initWithTarget:(id)target action:(SEL)action {    if (self = [super initWithTarget:target action:action]) {        self.target = target;        self.action = action;    }    return self;}- (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent *)event {    [super touchesBegan:touches withEvent:event];    if (touches.count > 1) {        self.state = UIGestureRecognizerStateFailed;        return;    }}- (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent *)event {    [super touchesMoved:touches withEvent:event];    UITouch *touch = [touches anyObject];    self.currentAngle = [self getTouchAngle:[touch locationInView:touch.view]];    self.previousAngle = [self getTouchAngle:[touch previousLocationInView:touch.view]];    if ([self.target respondsToSelector:self.action]) {        [self.target performSelector:self.action withObject:self];    }}- (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent *)event {    [super touchesEnded:touches withEvent:event];    [super setState:UIGestureRecognizerStateEnded];}- (void)touchesCancelled:(NSSet*)touches withEvent:(UIEvent *)event {    [super touchesCancelled:touches withEvent:event];    [super setState:UIGestureRecognizerStateCancelled];}- (float)getTouchAngle:(CGPoint)touch {    // Translate into cartesian space with origin at the center of a 320-pixel square    /*     *1.这里的view的width是320宽的     *2.相当于把view的原点从左上角，移动到中心点，并且把Y转的方向翻转，向上为正，并且0°位于Y轴     */    float x = touch.x - 160;    float y = -(touch.y - 160);    // Take care not to divide by zero!    if (y == 0) {        if (x > 0) {            return M_PI_2;        }        else {            return 3 * M_PI_2;        }    }    float arctan = atanf(x/y);    // Figure out which quadrant we're in    // Quadrant I 第一象限    if ((x >= 0) && (y > 0)) {        return arctan;    }    // Quadrant II 第二象限    else if ((x < 0) && (y > 0)) {        return arctan + 2 * M_PI;    }    // Quadrant III    else if ((x <= 0) && (y < 0)) {        return arctan + M_PI;    }    // Quadrant IV    else if ((x > 0) && (y < 0)) {        return arctan + M_PI;    }    return -1;}@end

在View上添加手势：

self.swirlGestureRecognizer = [[CAYSwirlGestureRecognizer alloc] initWithTarget:self action:@selector(rotationAction:)];[self.swirlGestureRecognizer setDelegate:self];[self.controlsView addGestureRecognizer:self.swirlGestureRecognizer];

action方法主要是做变换旋转：

- (void)rotationAction:(id)sender {    if([(CAYSwirlGestureRecognizer*)sender state] == UIGestureRecognizerStateEnded) {        return;    }    CGFloat direction = ((CAYSwirlGestureRecognizer*)sender).currentAngle - ((CAYSwirlGestureRecognizer*)sender).previousAngle;    bearing += 180 * direction / M_PI;    if (bearing < -0.5) {        bearing += 360;    }    else if (bearing > 359.5) {        bearing -= 360;    }    CGAffineTransform knobTransform = self.knob.transform;    CGAffineTransform newKnobTransform = CGAffineTransformRotate(knobTransform, direction);    [self.knob setTransform:newKnobTransform];    self.position.text = [NSString stringWithFormat:@"%dº", (int)lroundf(bearing)];}

最终的效果如下：

代码CayuseConcepts/KnobRotation

参考

• Gesture Recognizers
• UIGestureRecognizer Tutorial: Creating Custom Recognizers