UIGestureRecognizer

為了完成手勢識別，必須借助於手勢識別器—-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，用於縮放)
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:)];

敲擊實例

@interface GRViewController () 
@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

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

縮放和旋轉實例

@interface GRViewController () 
@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

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

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
};