self.view setNeedsDisplay and self.view setNeedsLayout are not working

Question

I have a main view controller showing on the screen and a class (delegate) running in the background getting positions. When I get the result I call the delegate method in the view controller to update the label on the screen. I tried several ways but still no update to the screen.

Here is the method:

-(void) updateDisplay
{

    NSLog(@"%@",myPosition.currentArea);
    _area.text = [NSString stringWithFormat:@"area = %@",myPosition.currentShopArea];


    //[self.view performSelectorOnMainThread:@selector(setNeedsDisplay) withObject:nil waitUntilDone:YES];
    [self.view setNeedsDisplay];
    //[self.view setNeedsLayout];
}

I check the console, it displays the correct area but on the screen still showing null. I tried all three ways (commented out above) but none of those update the screen.

Answer 1

You could try 2 things:

1. calling updateDisplay on the main thread:

   [delegate performSelectorOnMainThread:@selector(updateDisplay) withObject:nil waitUntilDone:YES];
   

   in the end, it is accessing UIKit, so better doing it right;

2. if that does not help, try with:

   [_area setNeedsDisplay];
   

   In this case also, if would be advisable to call the method on the main thread.