Overriding drawRect method in a UIView subclass & call it into another UIViewcontroller - ios

Question

I am a novice ios programmer and this is my first project.I am going to develop this project specifically for ipad. In this project i need to draw several circles & display data on it by parsing xml element.I have done the the circle drawing part by subclassing UIView class and overriding drawRect method. I load the UIView subclass in a UIViewcontroller via loadview method .Now what i need to do is
Touch a circle and switch to another UIViewcontroller.
I am not sure how to switch to another UIViewcontroller because all of drawing and touch detecting code is in my UIView subclass.
A help will be appreciated

Answer 1

You need to use a delegate method to tell the parent view controller that there was a touch, so it can present another view controller.
At the top of your UIView subclass header, add this:
#protocol MyCustomViewDelegate <NSObject>
- (void)customViewCircleTapped;
#end
Then, in your declaration of the view (the existing declaration you have of your custom view subclass):
#interface MyCustomView : UIView
...
#property (weak) id<MyCustomViewDelegate> delegate;
After that, in your view controller, you need to set view.delegate = self, so the view can reference the view controller.
Then, in your view controller header, change your declaration to look like this:
#interface MyViewController : UIViewController <MyCustomViewDelegate>
then implement customViewCircleTapped in the view controller implementation:
- (void)customViewCircleTapped {
... // Open a view controller or something
}
Once you have done that, in the touch detection code in your view, you can add:
[self.delegate customViewCircleTapped];
What this does is gives your custom view the ability to tell its parent view controller that something has happened, by calling this method (you can change it and add arguments if you need to pass data), and then the view controller can open another view controller or perform some action based on this.
View detects touches → Process touches → call customViewCircleTapped delegate method on view controller → view controller opens another view controller

Answer 2

Provide the subclassed view with a delegate notifying the view is touched and in the delegate call in the mainVC do the push job

Answer 3

The way I like to do this is to send a message up the responder chain. This completely decouples the view from it's enclosing views and view controllers. So, when your circle view is tapped, it emits a "circle view was tapped message" to the responder chain--the first object on the responder chain that responds to that message (which don't know/care which one) will have it invoked. It's simple to implement.
You attach a UITapGestureRecognizer to your view with -tapped: as the action.
On your view, your tap action might look like this.
-(IBAction)tapped:(UIGestureRecognizer*)g
{
[ self sendAction:#selector( circleViewTapped: ) withObject:self ] ;
}
The -sendAction: method on UIResponder is added via a category, like this:
#implementation UIResponder (ActionSending)
-(void)sendAction:(SEL)action withObect:(id)object
{
UIResponder * target = self ;
while( self && ![ target respondsToSelector:action ] )
{
target = [ target nextResponder ] ;
}
[ target performSelector:action withObject:object ] ;
}
#end
Your view controller or any parent view or parent view controller that responds to circleViewTapped: will have that method invoked when your circle view is tapped.
A note about organizing your views:
I would make a circle view UIView subclass. Instantiate your subclass for each circle to be displayed. To each of those attach a UITapGestureRecognizer. The target of your gesture recognizer is the -tapped: method, above.

Answer 4

The current answers are overcomplicating the solution. You don't need gesture recognisers or delegate protocols.
Make your circle drawing view a subclass of UIControl instead of UIView. Then attach your view controller as a target to the UIControlEventTouchUpInside event:
[circleView addTarget:self action:#selector(circleTapped:) forControlEvents:UIControlEventTouchUpInside];
This will call the circleTapped: method on your view controller, with the tapped view as the sender.