When the UILongPressGestureRecognizer begins recognizing I'd like to move the view to another view but when this happens the state changes to cancelled.

if (longPressGestureRecognizer.state == UIGestureRecognizerStateBegan) {
    
    [cellView removeFromSuperview];
    
    [self.anotherView addSubview:cellView];
}

Is there any way to preserve the gesture recognizer?

CodePudding user response：

Remove this line:

[cellView removeFromSuperview];

When you execute:

[self.anotherView addSubview:cellView];

UIKit will move the cellView from its current superview automatically and add it to anotherView.

That should prevent losing the state of the gesture recognizer.

Here's a quick example:

#import "LongPressViewController.h"

@interface LongPressViewController ()
{
    UIView *blueView;
    UIView *redView;
    UIView *yellowView;
}
@end

@implementation LongPressViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.view.backgroundColor = UIColor.systemBackgroundColor;
    
    blueView = [UIView new];
    redView = [UIView new];
    yellowView = [UIView new];
    
    blueView.backgroundColor = UIColor.systemBlueColor;
    redView.backgroundColor = UIColor.systemRedColor;
    yellowView.backgroundColor = UIColor.systemYellowColor;

    blueView.frame = CGRectMake(80, 100, 240, 240);
    redView.frame = CGRectOffset(blueView.frame, 0, 260);
    
    yellowView.frame = CGRectMake(20, 20, 80, 80);
    
    [blueView addSubview:yellowView];
    
    [self.view addSubview:blueView];
    [self.view addSubview:redView];
    
    UILongPressGestureRecognizer *g = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(lpHandler:)];
    [yellowView addGestureRecognizer:g];
    
}

- (void)lpHandler:(UILongPressGestureRecognizer *)longPressGestureRecognizer {
    
    CGPoint p = [longPressGestureRecognizer locationInView:yellowView];

    switch (longPressGestureRecognizer.state) {
        case UIGestureRecognizerStateBegan:
            [redView addSubview:yellowView];
            break;
            
        case UIGestureRecognizerStateChanged:
            NSLog(@"Changed: %@", [NSValue valueWithCGPoint:p]);
            break;
            
        case UIGestureRecognizerStateEnded:
            NSLog(@"Ended");
            break;
            
        default:
            break;
    }
    
}

@end

yellowView will start as a subview of blueView. When you long-press, it will "jump" to - and become a subview of - redView.

Keep the touch down, and as you drag you'll see the continuous logging of the touch location (relative to yellowView).

When you release the touch, we log "Ended"