Disable UITableView scrolling temporarily during drag - ios

Question

I am trying to figure out a way to temporarily (i.e. during a single drag gesture) disable scrolling on a UITableView and then re-enable it to have it pick up where it left off.
My reason is I have a gesture recognizer that is monitoring the drag, and if the user drags their finger above the top of the table, I want to resize the table upwards with their finger, to a point, and then stop resizing and continue scrolling again.
Naturally, I don't want the table to scroll while it is resizing, because that's effectively achieving the scroll itself (by moving the entire table view instead of the inner scrollable content), however I can't figure out how to do this in such a way that it allows the gesture to take effect again after a certain point (or if the user drags back down over the table).
Is there a way to temporarily disable/block a gesture without causing it to fail or cancel outright?
Perhaps I could write a subclass of UITableView that can intercept the gestures and ignore them as needed. What method should I override to do this?
Update:
I ended up approaching this in a different way, which is to simply adjust the contentOffset of the table view at each change of the gesture. I was afraid this might look "jittery" but it actually works quite smoothly. However I'll leave the question open as I'm still curious if this can be done.

Answer 1

At the request of #BrunoGalinari, here is the main part of my implementation of handling pan gestures on a UITableView without breaking the table view's intrinsic scrolling.
tableViewExpanded is a local property that switches between two layout states (expanded or not) and adjusts the bottomViewHeightConstraint constant appropriately. Setting it to itself just readjusts the constraint to one of the two valid values since it is also affected during the pan.
- (void)handlePan:(UIPanGestureRecognizer*)sender {
static CGFloat initialBottomViewY;
static CGFloat initialTableViewContentOffsetY;
static CGFloat initialTouchPointY;
CGPoint touchPoint = [sender locationInView:self.view];
CGFloat splitOffset = touchPoint.y - initialBottomViewY;
BOOL inEffect = ( sender == self.tableViewPan && touchPoint.y < initialBottomViewY ) || ( sender == self.mapViewPan && touchPoint.y > initialBottomViewY );
switch ( sender.state ) {
case UIGestureRecognizerStateBegan: {
initialBottomViewY = self.bottomView.y;
initialTableViewContentOffsetY = self.tableView.contentOffset.y;
initialTouchPointY = touchPoint.y;
break;
}
case UIGestureRecognizerStateEnded: {
self.dragVelocity = [sender velocityInView:self.view].y;
if ( inEffect ) {
if ( ABS( splitOffset ) > 60.f ) { // adjust
if ( sender == self.mapViewPan && touchPoint.y > initialBottomViewY )
self.tableViewExpanded = NO;
else if ( sender == self.tableViewPan && touchPoint.y < initialBottomViewY )
self.tableViewExpanded = YES;
else
self.tableViewExpanded = self.tableViewExpanded;
} else
self.tableViewExpanded = self.tableViewExpanded; // spring back
}
break;
}
case UIGestureRecognizerStateChanged: {
if ( inEffect ) {
self.tableView.contentOffset = CGPointMake( self.tableView.contentOffset.x, initialTableViewContentOffsetY + initialTouchPointY - initialBottomViewY );
self.bottomViewHeightConstraint.constant = self.view.height - touchPoint.y;
self.annotationToSelect = nil;
[self adjustMapAnimated:NO];
}
break;
}
default: {
break;
}
}
}
Here's what the window looks like, to get an idea of placement:

Answer 2

You can disable scrolling of a UITableView by setting:
table.scrollEnabled = NO;
When you are don't with you custom gesture, enable it:
table.scrollEnabled = YES;
It is a property of the parent class UIscrollView:
If the value of this property is YES , scrolling is enabled, and if it is NO , scrolling is disabled. The default is YES.
When scrolling is disabled, the scroll view does not accept touch events; it forwards them up the responder chain.