I want to have a view in which there are vehicles driving around that the user can also drag and drop. What do you think is the best large-scale strategy for doing this? Is it best to get touch events from the views representing the vehicles, or from the larger view? Is there a simple paradigm you've used for drag and drop that you're satisfied with? What are the drawbacks of different strategies?
Assume you have a UIView
scene with a background image and many vehicles
, you may define each new vehicle as a UIButton
(UIImageView will probably work too):
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
[button addTarget:self action:@selector(imageTouch:withEvent:) forControlEvents:UIControlEventTouchDown];
[button addTarget:self action:@selector(imageMoved:withEvent:) forControlEvents:UIControlEventTouchDragInside];
[button setImage:[UIImage imageNamed:@"vehicle.png"] forState:UIControlStateNormal];
[self.view addSubview:button];
Then you may move the vehicle wherever you want, by responding to the UIControlEventTouchDragInside
event, e.g.:
- (IBAction) imageMoved:(id) sender withEvent:(UIEvent *) event
{
CGPoint point = [[[event allTouches] anyObject] locationInView:self.view];
UIControl *control = sender;
control.center = point;
}
It's a lot easier for individual vehicle to handle its own drags, comparing to manage the scene as a whole.