从Cocoa中的视图访问子视图的drawRect方法

Question

I have my main iOS view, with an UIVIew as subview linked to a class (called graphView). My graphView has a drawRect method that is initiated upon application start.

Now, clicking on a button in the main view, I would like the sub UIView to refresh (so drawRect restarted) with specific parameters.

How can I do that, ie how can I access the graphView class that was initially instanced ?

Thanks

Answer 1

You can request to update the view by calling setNeedsDisplay on the UIView. Then the drawRect method should be called by the OS.

If you have created your subview in XCode designer, create an outlet of the UIView in the UIViewDelegate to get access to the subview instance.

Answer 2

You should have a property for your GraphView. Through this you can always access your Graphview inside your main viewcontroller, ie:

@property (strong, nonatomic) GraphView *graphView

which you would synthesize like this in your implementation:

@synthesize graphView = _graphView;

When a user now presses a button you could execute the following function:

- (void) buttonTouched:(id)sender
{
    [_graphView setNeedsDisplay];
}

This will mark _graphView as a view that needs to be redrawn, thus executing its drawRect: method in the next draw-cycle.