UIGestureRecognizer

為了完成手勢識別，必須借助于手勢識別器—-UIGestureRecognizer

利用UIGestureRecognizer，能輕松識別用戶在某個view上面做的一些常見手勢

UIGestureRecognizer是一個抽象類，定義了所有手勢的基本行為，使用它的子類才能處理具體的手勢

UITapGestureRecognizer       //(敲擊)
UIPinchGestureRecognizer     //(捏合，用于縮放)
UIPanGestureRecognizer       //(拖拽)
UISwipeGestureRecognizer     //(輕掃)
UIRotationGestureRecognizer  //(旋轉)
UILongPressGestureRecognizer //(長按)

敲擊 UITapGestureRecognizer

每一個手勢識別器的用法都差不多，比如UITapGestureRecognizer的使用步驟如下

創建手勢識別器對象
UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] init];

設置手勢識別器對象的具體屬性
// 連續敲擊2次
tap.numberOfTapsRequired = 2;
// 需要2根手指一起敲擊
tap.numberOfTouchesRequired = 2;
添加手勢識別器到對應的view上
[self.iconView addGestureRecognizer:tap];
監聽手勢的觸發
[tap addTarget:self action:@selector(tapIconView:)];</pre> 


 敲擊實例 

@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
/**

當點擊view的時候,會先調用這個方法
*/

(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.創建手勢識別器對象
  UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] init];
  // 連續敲擊2次,手勢才能識別成功
  tap.numberOfTapsRequired = 2;
  tap.numberOfTouchesRequired = 2;
// 2.添加手勢識別器對象到對應的view
  [self.iconView addGestureRecognizer:tap];
// 3.添加監聽方法(識別到了對應的手勢,就會調用監聽方法)
  [tap addTarget:self action:@selector(tapView)];
}

(void)tapView
{
  NSLog(@"-----我敲擊了屏幕！！");
}


@end</pre> 


 長按和輕掃實例 

@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)];
// 至少長按2秒
  longPress.minimumPressDuration = 2;
// 在觸發手勢之前,50px范圍內長按有效
  longPress.allowableMovement = 50;
[self.redView addGestureRecognizer:longPress];
}

(void)longPressView
{
  NSLog(@"長按了紅色的view");
}


@end</pre> 


 縮放和旋轉實例 

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

@implementation GRViewController

(void)viewDidLoad
{
  [super viewDidLoad];
[self testPinchAndRotate];
}


pragma mark - 手勢識別器的代理方法
/**

是否允許多個手勢識別器同時有效
Simultaneously : 同時地
*/

(BOOL)gestureRecognizer:(UIGestureRecognizer )gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer )otherGestureRecognizer
{
return YES;
}



pragma mark - 縮放 + 旋轉

(void)testPinchAndRotate
{
  [self testPinch];
  [self testRotate];
}

pragma mark - 縮放手勢(捏合手勢)

(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; // 這個真的很重要!!!!!
}


pragma mark - 旋轉手勢

(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; // 這個很重要!!!!!
}


@end</pre> 


 拖拽實例 

@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: // 開始觸發手勢

      break;

  case UIGestureRecognizerStateEnded: // 手勢結束

      break;

  default:
      break;

}
// 1.在view上面挪動的距離
  CGPoint translation = [pan translationInView:pan.view];
  CGPoint center = pan.view.center;
  center.x += translation.x;
  center.y += translation.y;
  pan.view.center = center;
// 2.清空移動的距離
  [pan setTranslation:CGPointZero inView:pan.view];
}


@end</pre> 


 手勢識別的狀態 

typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
    // 沒有觸摸事件發生，所有手勢識別的默認狀態
    UIGestureRecognizerStatePossible,
    // 一個手勢已經開始但尚未改變或者完成時
    UIGestureRecognizerStateBegan,
    // 手勢狀態改變
    UIGestureRecognizerStateChanged,
    // 手勢完成
    UIGestureRecognizerStateEnded,
    // 手勢取消，恢復至Possible狀態
    UIGestureRecognizerStateCancelled, 
    // 手勢失敗，恢復至Possible狀態
    UIGestureRecognizerStateFailed,
    // 識別到手勢識別
    UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded
};