how to know uitableview is pressed when empty - ios5

Question

i am making a chat application, and in the chat window there are uilabels in uitableviewcells. initially the keyboard will be present but when the user touches on any place on uitableview, i will make the chat window as fullscreen (dissappearing keyboard).
i cant find a way/trick to accomplish this.
i have tried the following method: by using tableview:didselectrowatindexpath, i am able to do it but, user needs to press on an existent uitableviewcell. but i want to understand the press even when uitableview is empty..
note: my chat tableview is interactive e.x. some rows will include image button which need to be pressable, so i cant just put an invisible button onto uitableview.
thank you for your thoughts
Aytunc Isseven

Answer 1

What you want to do is add a gesture recognizer to the UITableView that responds to the appropriate gestures. I would recommend against using UITapGestureRecognizer as the UITableView is already using taps for selecting the cells, so you might want to try the UILongPressGestureRecognizer. I put together a small sample of how you can do this as follows:
In my viewDidLoad I did the following:
UILongPressGestureRecognizer *gesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:#selector(handleLongPressFrom:)];
[self.tableView addGestureRecognizer:gesture];
and the handleLongPressFrom: is as follows:
- (void)handleLongPressFrom:(UILongPressGestureRecognizer *)recognizer {
NSLog(#"handleLongPressFrom: %#", recognizer);
// Add real code here
}
The full list of gestures can be found here.
Oh, if you did want to still use tap, check out this stack overflow question. I don't know if the method presented works fully, but it'd be a good place to start.
Using UITapGestureRecognizer with a UITableView:
Okay, since the tap gesture seems to be the correct one for your use case you can try and do the following. Step 1 is to set up the gesture recognizer as I listed above using the tap gesture instead of the long press gesture.
The code in viewDidLoad is very similar with an important addition ...
UITapGestureRecognizer *gesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleTapFrom:)];
// we need to set the gesture delegate so we can allow the tap to pass through to the
// UITableViewCell if necessary.
gesture.delegate = self;
[self.tableView addGestureRecognizer:gesture];
The handleTapFrom: function is pretty much the same with just the different gesture recognizer as the parameter.
- (void)handleTapFrom:(UITapGestureRecognizer *)recognizer {
NSLog(#"handleTapFrom: %#", recognizer);
// Add real code here
}
The major changes to this approach is that we need to implement the UIGestureRecognizerDelegate protocol. Since our goal is to allow the tap gesture to pass through the UITableView to it's subviews (i.e. the UITableViewCell and it's components) we need to implement the gestureRecognizer:shouldRecieveTouch: function. The following implementation should cover what you are attempting.
#pragma mark UIGestureRecognizerDelegate methods
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
// If the view that is touched is not the view associated with this view's table view, but
// is one of the sub-views, we should not recognize the touch.
if (touch.view != self.tableView && [touch.view isDescendantOfView:self.tableView]) {
return NO;
}
return YES;
}
The isDescendantOfView: function returns YES if the view it is testing against is the same as the view doing the testing, so we need to accommodate that case separately. You can generify this function by using gestureRecognizer.view instead of self.tableView, but I didn't think it was necessary in this case.

Answer 2

The trick is to make your viewController put a tap recognizer on the view but make it always opt out by returning NO from the delegate method "gestureRecognizerShouldBegin". That way gestureRecognizerShouldBegin gets called for every touch on the view, but you don't interfere with the normal event handling of the table.
- (void)viewDidLoad {
[super viewDidLoad];
[self detectTouchesOnView:self.tableView];
}
- (void)detectTouchesOnView:(UIView*)theView {
UITapGestureRecognizer* tapR = [[UITapGestureRecognizer alloc]initWithTarget:nil action:nil];
tapR.delegate = self;
[theView addGestureRecognizer:tapR];
}
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {
// React to the UITableView being touched E.G. by hiding the keyboard as below.
[self.view endEditing:YES];
return NO;
}