Question

I’m using a UIPanGestureRecognizer to recognize horizontal sliding in a UITableView (on a cell to be precise, though it is added to the table itself). However, this gesture recognizer obviously steals the touches from the table. I already got the pangesturerecognizer to recognize horizontal sliding and then snap to that; but if the user starts by sliding vertical, it should pass all events from that touch to the tableview.

One thing i have tried was disabling the recognizer, but then it wouldn’t scroll untill the next touch event. So i’d need it to pass the event right away then.

Another thing i tried was making it scroll myself, but then you will miss the persistent speed after stopping the touch.

Heres some code:

//In the viewdidload method
UIPanGestureRecognizer *slideRecognizer = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(sliding:)];
[myTable addGestureRecognizer:slideRecognizer];



-(void)sliding:(UIPanGestureRecognizer *)recognizer
{
    if (recognizer.state == UIGestureRecognizerStateBegan)
    {
    CGPoint translation = [recognizer translationInView:favoritesTable];
    if (sqrt(translation.x*translation.x)/sqrt(translation.y*translation.y)>1) {
        horizontalScrolling = YES; //BOOL declared in the header file
        NSLog(@"horizontal");
        //And some code to determine what cell is being scrolled:
        CGPoint slideLocation = [recognizer locationInView:myTable];
        slidingCell = [myTable indexPathForRowAtPoint:slideLocation];
        if (slidingCell.row == 0) {
            slidingCell = nil;
        }

    }
    else
    {
        NSLog(@"cancel");
    }

    if (recognizer.state == UIGestureRecognizerStateEnded || recognizer.state == UIGestureRecognizerStateCancelled)
    {
    horizontalScrolling = NO;
    }


    if (horizontalScrolling)
    {
        //Perform some code
    }
    else
    {
    //Maybe pass the touch from here; It's panning vertically
    }

}

So, any advice on how to pass the touches?

Addition: I also thought to maybe subclass the tableview’s gesture recognizer method, to first check if it’s horizontal; However, then i would need the original code, i suppose… No idea if Apple will have problems with it.
Also: I didn’t subclass the UITableView(controller), just the cells. This code is in the viewcontroller which holds the table 😉

Answer 1

I had the same issue and came up with a solution that works with the UIPanGestureRecognizer.

In contrast to Erik I’ve added the UIPanGestureRecognizer to the cell directly, as I need just one particular cell at once to support the pan. But I guess this should work for Erik’s case as well.

Here’s the code.

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)gestureRecognizer
{
    UIView *cell = [gestureRecognizer view];
    CGPoint translation = [gestureRecognizer translationInView:[cell superview]];

    // Check for horizontal gesture
    if (fabsf(translation.x) > fabsf(translation.y))
    {
        return YES;
    }

    return NO;
}

The calculation for the horizontal gesture is copied form Erik’s code – I’ve tested this with iOS 4.3.

Edit:
I’ve found out that this implementation prevents the “swipe-to-delete” gesture. To regain that behavior I’ve added check for the velocity of the gesture to the if-statement above.

if ([gestureRecognizer velocityInView:cell].x < 600 && sqrt(translate...

After playing a bit on my device I came up with a velocity of 500 to 600 which offers in my opinion the best user experience for the transition between the pan and the swipe-to-delete gesture.