8.2 Detecting Rotation Gestures

本文主要是介绍8.2 Detecting Rotation Gestures，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

旋转手势

@interface ViewController ()

@property (nonatomic, strong) UIRotationGestureRecognizer *rotationGestureRecognizer;

@property (nonatomic, strong) UILabel *helloWorldLabel;

/* We can remove the nonatomic and the unsafe_unretained marks from this property declaration. On a float value, the compiler will generate both these for us automatically */

@property (nonatomic, unsafe_unretained) CGFloat rotationAngleInRadians;

@end

@implementation ViewController

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

NSLog(@"%@ \nrotation=%f \nvelocity=%f",paramSender,paramSender.rotation,paramSender.velocity);

if (self.helloWorldLabel == nil){

return;

}

/* Take the previous rotation and add the current rotation to it */

self.helloWorldLabel.transform = CGAffineTransformMakeRotation(self.rotationAngleInRadians +

paramSender.rotation);

/* At the end of the rotation, keep the angle for later use */

if (paramSender.state == UIGestureRecognizerStateEnded){

self.rotationAngleInRadians += paramSender.rotation;

NSLog(@"rotationAngleInRadians=%f",self.rotationAngleInRadians);

}

- (void)viewDidLoad

{

[super viewDidLoad];

self.view.backgroundColor = [UIColor whiteColor];

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

self.helloWorldLabel.text = @"Hello, World!";

self.helloWorldLabel.font = [UIFont systemFontOfSize:66.0f];

[self.helloWorldLabel sizeToFit];

self.helloWorldLabel.center = self.view.center;

[self.view addSubview:self.helloWorldLabel];

self.rotationGestureRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self

action:@selector(handleRotations:)];

[self.view addGestureRecognizer:self.rotationGestureRecognizer];

}

- (void)didReceiveMemoryWarning

{

[super didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

@end

输出：

第一把旋转：

2014-04-10 09:35:01.240 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Began; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=0.001488

velocity=0.350469

2014-04-10 09:35:01.255 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Changed; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=0.018048

velocity=0.518359

……..

2014-04-10 09:35:02.487 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Changed; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=1.026013

velocity=0.039118

2014-04-10 09:35:02.503 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Changed; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=1.026013

velocity=0.039118

2014-04-10 09:35:02.519 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Ended; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=1.026013

velocity=0.039118

2014-04-10 09:35:02.521 cookbook[507:907] rotationAngleInRadians=1.026013

第二把旋转：

2014-04-10 09:38:56.187 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Began; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=0.000381

velocity=0.158696

2014-04-10 09:38:56.203 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Changed; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=0.002872

velocity=0.157695

2014-04-10 09:38:56.206 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Changed; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=0.002872

velocity=0.157695

……

…...

2014-04-10 09:38:56.619 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Changed; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=0.074877

velocity=0.064103

2014-04-10 09:38:56.683 cookbook[507:907] <UIRotationGestureRecognizer: 0x18faf0; state = Ended; view = <UIView 0x386250>; target= <(action=handleRotations:, target=<ViewController 0x3842b0>)>>

rotation=0.074877

velocity=0.064103

2014-04-10 09:38:56.685 cookbook[507:907] rotationAngleInRadians=1.100890

CGAffineTransformMakeRotation

看到这个函数了没，学校里学的转换的知识还记得吗，要不要赶紧复习下