(iOS) Touches, taps and Gestures

1.Theory.mm

//Touch events must be implemented in the class for ex. of the control that should handle it. If it doesn't it has to be
//implemented in the parent class (ex. if not in the uicontrol, uibutton,table cell, tableview etc then it will go to UIView.
//If UIView won't handle it, then it will go to the ViewController class. It can end up to the appdelegate class).
//You have to call the parent's function that will implement the event manually

//Four methods are used to notify a responder about touches.

//When the user first touches the screen, the system looks for a responder that has a method called touchesBegan:withEvent:
//Example
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    //How many taps were there
    //UITouch *touch = [touches anyObject];
    NSUInteger numTaps = [[touches anyObject] tapCount];

    //Number of touches (fingers) currently pressed
    NSUInteger numTouches = [touches count];
    // Do something here.
}   //If numTaps=2 and numTouches=2 the user doubled tapped with both fingers


//Some times some controls don't care about touches in other controls.
//You can get a subset of touches that has only those touches that fall within a particular view from the event, like so
NSSet *myTouches = [event touchesForView:self.view];

//Every UITouch represents a different finger
//Each finger is located at a different position on the screen
//You can find out the position of a specific finger using the UITouch object
CGPoint point = [touch locationInView:self];

//You can get notified while the user is moving fingers across the screen by implementing 
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
//This method is called multiple times during a long drag
//Each time it is called, you will get another set of touches and another event

//you can also discover the previous location of a touch, which is the finger’s position the last time
//either touchesMoved:withEvent: or touchesBegan:withEvent: was called.

//When the user’s fingers are removed from the screen 
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
//is invoked


//If the user is in the middle of a gesture when something happens to interrupt it, like the phone ringing, this
-(void)touchesCancelled(NSSet *)touches withEvent:(UIEvent *)event
//is called

2.CustomSwipe.mm

/*****************************************************/
//Vertical and Horizaontal Swipe
/*****************************************************/

@property (nonatomic) CGPoint gestureStartPoint;
----------------------------------

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    //Grab any touch (we don't care about multiple touches here)
    UITouch *touch = [touches anyObject];

  //Getting the position of the touch
    self.gestureStartPoint = [touch locationInView:self.view];
}


- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    //Get the current position of the user's finger
    UITouch *touch = [touches anyObject];
    CGPoint currentPosition = [touch locationInView:self.view];

    //Calculate how far the user’s finger has moved both horizontally and vertically from its starting position
    //fabsf returns absolute value of float
    CGFloat deltaX = fabsf(self.gestureStartPoint.x - currentPosition.x);
    CGFloat deltaY = fabsf(self.gestureStartPoint.y - currentPosition.y);

    //check to see if the user has moved far enough in one direction
    //without having moved too far in the other to constitute a swipe.
    if (deltaX >= kMinimumGestureLength && deltaY <= kMaximumVariance) 
    {
        //Horizontal swipe detected

        [self performSelector:@selector(eraseText) withObject:nil afterDelay:2];
    } 
    else if (deltaY >= kMinimumGestureLength && deltaX <= kMaximumVariance)
    {
        //Vertical swipe detected
        [self performSelector:@selector(eraseText) withObject:nil afterDelay:2];
    }
}

3.SingleSwipeWithGestureRecognizer.mm

- (void)reportHorizontalSwipe:(UIGestureRecognizer *)recognizer
{
    //Horizontal swipe detected
    [self performSelector:@selector(eraseText) withObject:nil afterDelay:2];
}


- (void)reportVerticalSwipe:(UIGestureRecognizer *)recognizer
{
    //Vertical swipe detected
    [self performSelector:@selector(eraseText) withObject:nil afterDelay:2];
}


- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    UISwipeGestureRecognizer *vertical = [[UISwipeGestureRecognizer alloc] 
                                                      initWithTarget:self action:@selector(reportVerticalSwipe:)];

    vertical.direction = UISwipeGestureRecognizerDirectionUp | UISwipeGestureRecognizerDirectionDown;

    //Instead of self.view we could put any control. Label. button, imageview etc..
    [self.view addGestureRecognizer:vertical];


    UISwipeGestureRecognizer *horizontal = [[UISwipeGestureRecognizer alloc]
                                                    initWithTarget:self action:@selector(reportHorizontalSwipe:)];

    horizontal.direction = UISwipeGestureRecognizerDirectionLeft| UISwipeGestureRecognizerDirectionRight;

    [self.view addGestureRecognizer:horizontal];
}



    /***************************************************/
    //Let's say you want to put a swipe in a cell at the cellforrow function

    // add swipe gesture to the cell so more options will appear
    UISwipeGestureRecognizer *swipe = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(cellSwiped:)];
    swipe.direction = UISwipeGestureRecognizerDirectionLeft| UISwipeGestureRecognizerDirectionRight;
    [cell addGestureRecognizer:swipe];



    #pragma mark - Cell is swiped

    -(void) cellSwiped:(UIGestureRecognizer *)recognizer {
        
        CGPoint location = [recognizer locationInView:self.tableView];
        NSIndexPath *swipedIndexPath = [self.tableView indexPathForRowAtPoint:location];
        TweetCell *swipedcell = (TweetCell*) [self.tableView cellForRowAtIndexPath:swipedIndexPath];
    
        [swipedcell toggleSwipedView];
    }

4.MultipleSwipesWithGestureRecognizer.mm

- (void)reportHorizontalSwipe:(UIGestureRecognizer *)recognizer
{
    self.label.text = [NSString stringWithFormat:@"%@Horizontal swipe detected",
                       [self descriptionForTouchCount:[recognizer numberOfTouches]]];

    [self performSelector:@selector(eraseText) withObject:nil afterDelay:2];
}
- (void)reportVerticalSwipe:(UIGestureRecognizer *)recognizer
{
    self.label.text = [NSString stringWithFormat:@"%@Vertical swipe detected",
                       [self descriptionForTouchCount:[recognizer numberOfTouches]]];

    [self performSelector:@selector(eraseText) withObject:nil afterDelay:2];
}

- (NSString *)descriptionForTouchCount:(NSUInteger)touchCount
{
    switch (touchCount) 
    {
        case 1:
            return @"Single";
        case 2:
            return @"Double ";
        case 3:
            return @"Triple ";
        case 4:
            return @"Quadruple ";
        case 5:
            return @"Quintuple ";
        default:
            return @""; 
    }
}


- (void)viewDidLoad
{
      [super viewDidLoad];
      // Do any additional setup after loading the view, typically from a nib. for (NSUInteger touchCount = 1; touchCount <= 5; touchCount++) {
        
      UISwipeGestureRecognizer *vertical;
      vertical = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(reportVerticalSwipe:)];
      vertical.direction = UISwipeGestureRecognizerDirectionUp | UISwipeGestureRecognizerDirectionDown;

      //Number of fingers required
      vertical.numberOfTouchesRequired = touchCount;

      [self.view addGestureRecognizer:vertical];


      UISwipeGestureRecognizer *horizontal;
      horizontal = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(reportHorizontalSwipe:)];
      horizontal.direction = UISwipeGestureRecognizerDirectionLeft | UISwipeGestureRecognizerDirectionRight;

      //Number of fingers required
      horizontal.numberOfTouchesRequired = touchCount;

      [self.view addGestureRecognizer:horizontal];

      /****************************************************/
      //OR FOR TAPS

      UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doSingleTap)];
      singleTap.numberOfTapsRequired = 1;

      [self.view addGestureRecognizer:singleTap];

      UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doDoubleTap)];
      doubleTap.numberOfTapsRequired = 2;

      [self.view addGestureRecognizer:doubleTap];

      //In order not to fire the "singleTap" method when the user double taps the screen
      //We'll tell it to fire up only if the doubleTap gesture fails
      [singleTap requireGestureRecognizerToFail:doubleTap];
}

5.CheckMarkGestureClass.mm

//This is a class that will be used by the viewcontroller where the user will make a checkmark

#import "CGPointUtils.h"
//contains declarations that are intended for use only by a subclass
#import <UIKit/UIGestureRecognizerSubclass.h>


@implementation CheckMark {
CGPoint lastPreviousPoint;
CGPoint lastCurrentPoint;
CGFloat lineLengthSoFar;
}
-------------------------------------

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesBegan:touches withEvent:event];

    UITouch *touch = [touches anyObject];
    CGPoint point = [touch locationInView:self.view];

    lastPreviousPoint = point;
    lastCurrentPoint = point;
    lineLengthSoFar = 0.0f;
}


- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesMoved:touches withEvent:event];

    UITouch *touch = [touches anyObject];

    CGPoint previousPoint = [touch previousLocationInView:self.view];
    CGPoint currentPoint = [touch locationInView:self.view];

    CGFloat angle = angleBetweenLines(lastPreviousPoint,
                                      lastCurrentPoint,
                                      previousPoint,
                                      currentPoint);

    if (angle >= kMinimumCheckMarkAngle && angle <= kMaximumCheckMarkAngle && lineLengthSoFar > kMinimumCheckMarkLength) 
    {
        self.state = UIGestureRecognizerStateEnded;
    }

    lineLengthSoFar += distanceBetweenPoints(previousPoint, currentPoint);
    lastPreviousPoint = previousPoint;
    lastCurrentPoint = currentPoint;
}


--------------------------------------------------------

//NOW IN THE VIEW CONTROLLER

- (void)viewDidLoad
{
    [super viewDidLoad];
        // Do any additional setup after loading the view, typically from a nib.

    CheckMark *check = [[CheckMark alloc] initWithTarget:self action:@selector(doCheck:)];

    [self.view addGestureRecognizer:check];
}

6.PinchAndRotate.mm

//In the .h file we have to conform to the below protocol
//in order to allow serveral gesture recognizers to recognize gestures simultaneously

@interface BIDViewController : UIViewController <UIGestureRecognizerDelegate>
@property (strong, nonatomic) UIImageView *imageView;
@end

-------------------------------------

@implementation BIDViewController { 
  CGFloat scale, previousScale; 
  CGFloat rotation, previousRotation;
}

- (void)viewDidLoad
{
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.

    previousScale = 1;

    UIImage *image = [UIImage imageNamed:@"yosemite-meadows.png"];
    self.imageView = [[UIImageView alloc] initWithImage:image];
    self.imageView.userInteractionEnabled = YES;
    self.imageView.center = CGPointMake(160, 160);

    [self.view addSubview:self.imageView];

    UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(doPinch:)];
    pinchGesture.delegate = self;

    [self.imageView addGestureRecognizer:pinchGesture];


    UIRotationGestureRecognizer *rotationGesture = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(doRotate:)];
    rotationGesture.delegate = self;
    
    [self.imageView addGestureRecognizer:rotationGesture];
}

//we always return YES to allow our pinch and rotation gestures to work together.
//Otherwise, the gesture recognizer that starts first would always block the other.
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer
shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
  return YES; 
}


- (void)transformImageView
{
    CGAffineTransform t = CGAffineTransformMakeScale(scale * previousScale,
                                                     scale * previousScale);
    t = CGAffineTransformRotate(t, rotation + previousRotation);
    self.imageView.transform = t;
}


- (void)doPinch:(UIPinchGestureRecognizer *)gesture
{
    scale = gesture.scale;
    [self transformImageView];

    if (gesture.state == UIGestureRecognizerStateEnded) 
    {
        previousScale = scale * previousScale;
        scale = 1;
    }
}



- (void)doRotate:(UIRotationGestureRecognizer *)gesture
{
    rotation = gesture.rotation;

    [self transformImageView];

    if (gesture.state == UIGestureRecognizerStateEnded) 
    {
        previousRotation = rotation + previousRotation;
        rotation = 0;
    }
}