Get swipe direction in Cocoa Touch

问题:

I am trying to catch a gesture but it does not work. Here is my code:

UISwipeGestureRecognizer *recognizer;
    recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
    [recognizer setDirection:(UISwipeGestureRecognizerDirectionRight | UISwipeGestureRecognizerDirectionLeft)];
    [[self view] addGestureRecognizer:recognizer];
    [recognizer release]; 

and

-(void)handleSwipeFrom:(UISwipeGestureRecognizer *)recognizer {
    NSLog(@"get gesture");
    if (recognizer.direction == UISwipeGestureRecognizerDirectionRight) {
        NSLog(@"get gesture right");
    }
    if (recognizer.direction == UISwipeGestureRecognizerDirectionLeft) {
        NSLog(@"get gesture Left");
    }
}

It always gets a gesture but does not recognize the direction. I also tried if(recognizer.direction){NSLog(@"get gesture");} and it also worked, so I do not understand where I made the mistake.

Thanks for any help.

回答1:

You're not using the UISwipeGestureRecognizercorrectly. Its direction is always going to be what you've set it to (in this case UISwipeGestureRecognizerDirectionRight | UISwipeGestureRecognizerDirectionLeft, or 3).

If you want to capture swipes left and right that you can differentiate between, you'll have to set up a separate recognizer for each. Apple does this in their SimpleGestureRecognizers sample.

回答2:

What you have to do is just change the codes for adding gesture recognizer.

UISwipeGestureRecognizer *leftRecognizer;
leftRecognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
[leftRecognizer setDirection: UISwipeGestureRecognizerDirectionLeft];
[[self view] addGestureRecognizer:leftRecognizer];
[leftRecognizer release];

UISwipeGestureRecognizer *rightRecognizer;
rightRecognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
[rightRecognizer setDirection: UISwipeGestureRecognizerDirectionRight];
[[self view] addGestureRecognizer:rightRecognizer];
[rightRecognizer release];  

回答3:

UISwipe... is iOS. But for Cocoa, you can use -swipeWithEvent: in your view class. See the documentation at: http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/EventOverview/HandlingTouchEvents/HandlingTouchEvents.html#//apple_ref/doc/uid/10000060i-CH13-SW10

回答4:

Both gypsicoder and paulbailey's answers are right. For a more detailed solution of mine, see: https://stackoverflow.com/a/16810160/936957