How Touch drag enter works? - ios

Question

Can anyone give me an example about Touch drag enter to drag from a button to another that triggering both button's event.
And how does it work?
For example, I want to drag from Do to Fa that event of Do, Re, Mi, Fa are triggered.
Here is my code:
- (void) setupVC {
soundBankPlayer = [[SoundBankPlayer alloc] init];
[soundBankPlayer setSoundBank:#"Piano"];
arrMusicalNotes = [NSArray arrayWithObjects:#"60", #"62", #"64", #"65", #"67", #"69", #"71", #"72", nil];
}
#pragma mark - Setup Musical Note
- (IBAction)btnMusicalNoteclick:(id)sender {
int numOfNote = [[arrMusicalNotes objectAtIndex:((UIButton*)sender).tag] intValue];
NSLog(#"%i", numOfNote);
[soundBankPlayer queueNote:numOfNote gain:1.0f];
[soundBankPlayer playQueuedNotes];
}
- (IBAction)btnDragOut:(id)sender {
NSLog(#"Out");
}
Oh I've seen that when i hold click out of Simulator, the method btnDragOut is triggered. And when i drag from out of Simulator to the button, the method of this button is triggered.
Now I want the method btnDragOut is triggered when i drag out of a button (finger is still in Simulator). Anyone know that?

Answer 1

You can add UIPanGestureRecognizer to your view of your UIViewController subclass via Storyboard or via code in viewDidLoad method:
UIPanGestureRecognizer *gestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(handleDrag:)];
[self.view addGestureRecognizer:gestureRecognizer];
Then you can add property in implementation file of your UIViewController subclass of current UIButton being dragged:
#interface YourViewController ()
#property (weak, nonatomic) UIButton *currentButton;
#end
Now in action method you can detect UIControlEventTouchDragEnter and UIControlEventTouchDragExit events as follows:
- (void)handleDrag:(UIPanGestureRecognizer *)gestureRecognizer
{
CGPoint point = [gestureRecognizer locationInView:self.view];
UIView *draggedView = [self.view hitTest:point withEvent:nil];
if (gestureRecognizer.state == UIGestureRecognizerStateChanged) {
if ([draggedView isKindOfClass:[UIButton class]] && !self.currentButton) {
self.currentButton = (UIButton *)draggedView;
NSLog(#"Enter: %ld", (long)self.currentButton.tag);
// send enter event to your button
[self.currentButton sendActionsForControlEvents:UIControlEventTouchDragEnter];
}
if (self.currentButton && ![self.currentButton isEqual:draggedView]) {
NSLog(#"Out: %ld", (long)self.currentButton.tag);
// send exit event to your button
[self.currentButton sendActionsForControlEvents:UIControlEventTouchDragExit];
self.currentButton = nil;
}
} else if (gestureRecognizer.state == UIGestureRecognizerStateEnded) {
self.currentButton = nil;
}
}