How to make a combined gestures?

Question

I want to ask some interesting thing. I want my app can action when a custom combined gestures occur. For example: call a action(/method) when user swipe left, top, left without the finger leave on the screen. How can i make this custom gesture?

and second question is can i swipe upper left( like " ／　" this direction)? How to make this gesture?

can anyone one help me? please! thanks

Answer 1

Well, conceptually you need to subclass UIGestureRecognizer, do some position tracking, and make use of the fact that after importing UIGestureRecognizerSubclass.h the gestures state property becomes read/write to move all the gears around yourself. As and example, I'll include a basic prototype for a diagonal gesture that I tried to build a long time ago. (It needs a few kinks worked out, but overall, it works.)

.H

#import <UIKit/UIKit.h>
#import <UIKit/UIGestureRecognizerSubclass.h>

@interface MMDiagnoalSwipeGestureRecognizer : UIGestureRecognizer
@property (nonatomic, readwrite) BOOL shouldReverseYDelta;
@property (nonatomic, readwrite) CGFloat tolerance;
@property (nonatomic, readonly) CGFloat angleOfSwipe;
@end

.M

#import "MMDiagnoalSwipeGestureRecognizer.h"
@interface MMDiagnoalSwipeGestureRecognizer ()
@property (nonatomic, readwrite) CGPoint startingPoint;
@end

@implementation MMDiagnoalSwipeGestureRecognizer


- (id)initWithTarget:(id)target action:(SEL)action {
    self = [super initWithTarget:target action:action];
    if (self) {
        _shouldReverseYDelta = NO;
        _tolerance = 30.0f;
    }
    return self;
}

- (CGFloat)angleOfGestureFromPoint:(CGPoint)start toEndPoint:(CGPoint)end {
    CGFloat deltaY = (_shouldReverseYDelta) ? end.y - start.y : start.y - end.y;
    CGFloat deltaX = end.x - start.x;

    _angleOfSwipe = atan2f(deltaY, deltaX) * 180.0f / M_PI;

    return _angleOfSwipe;
}

- (CGFloat)diagonalDistanceFromPoint:(CGPoint)start toEndPoint:(CGPoint)end {
    CGFloat deltaX = fabsf(start.x - end.x);
    CGFloat deltaY = fabsf(start.y - end.y);

    CGFloat hypotenuse = powf(deltaX, 2.0f) + powf(deltaY, 2.0f);

    return sqrtf(hypotenuse);
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    if (touches.count > 1) {
        if (self.state == UIGestureRecognizerStatePossible) {
            self.state = UIGestureRecognizerStateFailed;
        }
    }else{
        [touches enumerateObjectsUsingBlock:^(id obj, BOOL *stop) {
            UITouch *touch = (UITouch *)obj;
            _startingPoint = [touch locationInView:self.view];
        }];
    }
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

    [touches enumerateObjectsUsingBlock:^(id obj, BOOL *stop) {
        UITouch *touch = (UITouch *)obj;
        CGPoint endPoint = [touch locationInView:self.view];
        CGFloat angle = [self angleOfGestureFromPoint:_startingPoint toEndPoint:endPoint];

        if (self.state == UIGestureRecognizerStatePossible) {
            if ([self angleIsWithinDiagonalTolerance:angle] == YES) {
                if ([self diagonalDistanceFromPoint:_startingPoint toEndPoint:endPoint] >= 20.0f) {
                    self.state = UIGestureRecognizerStateRecognized;
                }
            }else{
                self.state = UIGestureRecognizerStateFailed;
            }
        }
    }];
}

- (BOOL)angleIsWithinDiagonalTolerance:(CGFloat)angle
{
//    NSLog(@"%s",__PRETTY_FUNCTION__);
    NSAssert1(_tolerance < 45.0f, @"DiagonalSwipeGestureRecognizer Error: tolerance property must be set to a value less than 45.0f. Otherwise, the gesture will be detected at any angle. If you don't care and want the swipe to be recognized at any angle, remove the NSAssert call from - %s.", __PRETTY_FUNCTION__);
//    NSAssert(_tolerance < 45.0f, @"DiagonalSwipeGestureRecognizer Error: tolerance property must be set to a value less than 45.0f. Otherwise, the gesture will be detected at any angle. If you don't care and want the swipe to be recognized at any angle, remove the NSAssert call from -[MMDiagnoalGestureRecognizer angleIsWithinDiagonalTolerance:].");

    if (angle >= 45.0f - _tolerance && angle <= 45.0f + _tolerance) {
        return YES;
    }else if (angle <= - (45.0f - _tolerance) && angle >= - (45.0f + _tolerance)) {
        return YES;
    }else if (angle >= 135.0f - _tolerance && angle <= 135.0f + _tolerance) {
        return YES;
    }else if (angle <= - (135.0f - _tolerance) && angle >= - (135.0f + _tolerance)) {
        return YES;
    }else{
        return NO;
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    [self touchesEnded:touches withEvent:event];
    self.state = UIGestureRecognizerStateChanged;
}

- (void)reset {
    //don't call, will be called automatically.
}



@end