UIGestureRecognizer

为了完成手势识别，必须借助于手势识别器—-UIGestureRecognizer

利用UIGestureRecognizer，能轻松识别用户在某个view上面做的一些常见手势

UIGestureRecognizer是一个抽象类，定义了所有手势的基本行为，使用它的子类才能处理具体的手势

UITapGestureRecognizer       //(敲击)
UIPinchGestureRecognizer     //(捏合，用于缩放)
UIPanGestureRecognizer       //(拖拽)
UISwipeGestureRecognizer     //(轻扫)
UIRotationGestureRecognizer  //(旋转)
UILongPressGestureRecognizer //(长按)

敲击 UITapGestureRecognizer

每一个手势识别器的用法都差不多，比如UITapGestureRecognizer的使用步骤如下

创建手势识别器对象
UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] init];

设置手势识别器对象的具体属性
// 连续敲击2次
tap.numberOfTapsRequired = 2;
// 需要2根手指一起敲击
tap.numberOfTouchesRequired = 2;

添加手势识别器到对应的view上
[self.iconView addGestureRecognizer:tap];

监听手势的触发
[tap addTarget:self action:@selector(tapIconView:)];

敲击实例

@interface GRViewController () <UIGestureRecognizerDelegate>
@property (weak, nonatomic) IBOutlet UIImageView *iconView;

@end

@implementation GRViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self testTap2];
}

- (void)testTap2
{
    UIGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapView)];
    tap.delegate = self;
    [self.iconView addGestureRecognizer:tap];
}

#pragma mark - 代理方法
/**
 *  当点击view的时候,会先调用这个方法
 */
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    CGPoint pos = [touch locationInView:touch.view];
    if (pos.x <= self.iconView.frame.size.width * 0.5) {
        return YES;
    }
    return NO;
}

- (void)testTap
{
    // 1.创建手势识别器对象
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] init];
    // 连续敲击2次,手势才能识别成功
    tap.numberOfTapsRequired = 2;
    tap.numberOfTouchesRequired = 2;

    // 2.添加手势识别器对象到对应的view
    [self.iconView addGestureRecognizer:tap];

    // 3.添加监听方法(识别到了对应的手势,就会调用监听方法)
    [tap addTarget:self action:@selector(tapView)];
}

- (void)tapView
{
    NSLog(@"-----我敲击了屏幕！！");
}

@end

长按和轻扫实例

@interface GRViewController ()
@property (weak, nonatomic) IBOutlet UIView *redView;

@end

@implementation GRViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    UISwipeGestureRecognizer *swipe = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipeView)];

    swipe.direction = UISwipeGestureRecognizerDirectionUp;

    [self.redView addGestureRecognizer:swipe];
}

- (void)swipeView
{
    NSLog(@"swipeView");
}

- (void)testLongPress
{
    UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] init];
    [longPress addTarget:self action:@selector(longPressView)];

    // 至少长按2秒
    longPress.minimumPressDuration = 2;

    // 在触发手势之前,50px范围内长按有效
    longPress.allowableMovement = 50;

    [self.redView addGestureRecognizer:longPress];
}

- (void)longPressView
{
    NSLog(@"长按了红色的view");
}

@end

缩放和旋转实例

@interface GRViewController () <UIGestureRecognizerDelegate>
@property (weak, nonatomic) IBOutlet UIImageView *iconView;
@end

@implementation GRViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self testPinchAndRotate];
}

#pragma mark - 手势识别器的代理方法

/**
 *  是否允许多个手势识别器同时有效
 *  Simultaneously : 同时地
 */
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

#pragma mark - 缩放 + 旋转
- (void)testPinchAndRotate
{
    [self testPinch];
    [self testRotate];
}

#pragma mark - 缩放手势(捏合手势)
- (void)testPinch
{
    UIPinchGestureRecognizer *pinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchView:)];
    pinch.delegate = self;
    [self.iconView addGestureRecognizer:pinch];
}

- (void)pinchView:(UIPinchGestureRecognizer *)pinch
{
    pinch.view.transform = CGAffineTransformScale(pinch.view.transform, pinch.scale, pinch.scale);
    pinch.scale = 1; // 这个真的很重要!!!!!
}

#pragma mark - 旋转手势
- (void)testRotate
{
    UIRotationGestureRecognizer *recognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotateView:)];
    recognizer.delegate = self;
    [self.iconView addGestureRecognizer:recognizer];
}

- (void)rotateView:(UIRotationGestureRecognizer *)recognizer
{
    recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
    recognizer.rotation = 0; // 这个很重要!!!!!
}

@end

拖拽实例

@interface GRViewController ()
@property (weak, nonatomic) IBOutlet UIView *purpleView;

@end

@implementation GRViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panView:)];
    [self.purpleView addGestureRecognizer:pan];
}

- (void)panView:(UIPanGestureRecognizer *)pan
{

    switch (pan.state) {
        case UIGestureRecognizerStateBegan: // 开始触发手势

            break;

        case UIGestureRecognizerStateEnded: // 手势结束

            break;

        default:
            break;
    }

    // 1.在view上面挪动的距离
    CGPoint translation = [pan translationInView:pan.view];
    CGPoint center = pan.view.center;
    center.x += translation.x;
    center.y += translation.y;
    pan.view.center = center;

    // 2.清空移动的距离
    [pan setTranslation:CGPointZero inView:pan.view];
}

@end

手势识别的状态

typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
    // 没有触摸事件发生，所有手势识别的默认状态
    UIGestureRecognizerStatePossible,
    // 一个手势已经开始但尚未改变或者完成时
    UIGestureRecognizerStateBegan,
    // 手势状态改变
    UIGestureRecognizerStateChanged,
    // 手势完成
    UIGestureRecognizerStateEnded,
    // 手势取消，恢复至Possible状态
    UIGestureRecognizerStateCancelled, 
    // 手势失败，恢复至Possible状态
    UIGestureRecognizerStateFailed,
    // 识别到手势识别
    UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded
};