Touch UITableView background while scrolling (Kind of an easter egg) - objective-c

Question

I need to do a hidden button at the bottom of the table view, not in a cell, in the background of the table view itself.
I saw something like this in a game "Where is my water", if you scroll out of bounds you can find a hidden button.
first, I created a simple button, and placed in the bottom of the table view
self.tableView.backgroundColor = [UIColor purpleColor]; //just to see better
UIButton *venom = [[UIButton alloc] initWithFrame:CGRectMake(50.0, self.tableView.contentSize.height+80.0, 100.0, 40.0)];
venom.backgroundColor = [UIColor redColor];
[venom addTarget:self action:#selector(venomAction) forControlEvents:UIControlEventTouchDown];
[self.tableView addSubview:venom];
Because of the self.tableView.contentSize.height+80.0, I need to scroll out of the bounds of the table view to see the button, having something like this:
The result is correct, I want this to be sort of hidden, but the problem is, I cannot click on the button, to see the button, I need to be scrolling and I cannot multitouch.
Can anyone assist me with that? or point me to the right direction

Answer 1

I'd make the button not the tableView's subview, but rather a sibling view above the tableView.
For example, your code could look like this
- (void)viewDidLoad {
[super viewDidLoad];
// Just creating a simple UITableView
UITableView *tableView = [[UITableView alloc] initWithFrame:self.view.bounds];
tableView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
tableView.dataSource = self;
tableView.delegate = self;
self.tableView = tableView;
[self.view addSubview:tableView];
// Creating the Easter Egg Button
UIButton *easterEggButton = [UIButton buttonWithType:UIButtonTypeSystem];
[easterEggButton setTitle:#"Easter Egg Button" forState:UIControlStateNormal];
[easterEggButton addTarget:self
action:#selector(easterEggButtonPressed)
forControlEvents:UIControlEventTouchUpInside];
self.easterEggButton = easterEggButton;
// NOTE that we add the Easter Egg Button to self.view over the Table View, not into Table View
[self.view addSubview:easterEggButton];
}
So we have the button placed over the tableView. This detaches it from interfering with tableView's gestureRecognizer.
Now you need some code to adjust the button's frame to be placed somewhere under the tableView's last cell. It may look something like this:
- (void)updateButtonFrame {
UIButton *button = self.easterEggButton;
// Just the easiest way calculate the width and height of the button depending on it's content
[button sizeToFit];
CGRect frame = button.bounds;
// Now, we want to place the button under all the cells
frame.origin.y = self.tableView.contentSize.height;
frame.origin.y += 60.0f; // add some padding to place it even lower
/* We have calculated button's frame in tableView's coordinate space, so we need to convert it to
* button superview's coordinate space. */
frame = [self.tableView convertRect:frame toView:button.superview];
// And finally apply the frame to the button
button.frame = frame;
}
And of course you need to call this layout method in appropriate moments, that is, whenever tableView reloads it's data (because contentSize may change), and whenever tableView scrolls.
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
/* Button resides in self.view and is unaware of Table View scrolling, so we need to update
* it's frame whenever Table View's content offset changes */
[self updateButtonFrame];
}
You may also call it viewDidLayoutSubviews to be safe if tableView's cell height depends on screen orientation and such.
- (void)viewDidLayoutSubviews {
[super viewDidLayoutSubviews];
// It's safe to recalculate button's frame whenever self.view layout updates
[self updateButtonFrame];
}
You may have a look at this example implementation
https://gist.github.com/bartekchlebek/429906e05fcbd976291d