无法在iOS 8中更改UIView背景颜色和UILabel文本颜色

Question

I've looked at many posts and none seem to help with the current issue I'm experiencing. I am trying to change the UIView background color and UILabel text color programmatically on a button click. They are all connected in the interface builder. What I did was open the ViewController.h file next to the Main.storyboard and clicked and dragged to connect the view (backgroundView) and label (letterR).

If anyone can see what I am doing wrong that would be great thanks!

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController{

    IBOutlet UIView *backgroundView;
    IBOutlet UILabel *letterR;
}

@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()
@end

@implementation ViewController

static int flag = 0;

- (void)viewDidLoad {
    [super viewDidLoad];
}

- (IBAction)ButtonClick:(id)sender {

    if(flag == 0){

        flag = 1;
        letterR.textColor = [UIColor blackColor];
        backgroundView.backgroundColor = [UIColor whiteColor];
    }

    else if(flag == 1){

        flag = 0;
        letterR.textColor = [UIColor whiteColor];
        backgroundView.backgroundColor = [UIColor colorWithRed:0 green:1 blue:1 alpha:1];
    }
}

@end

When monitoring the NSLog output of the label and background this is what I am getting:

Letter R: 2014-11-26 15:18:18.358 Rave[3923:340203] Letter R: >

Printing the color of the letter:(null)

Background: 2014-11-26 15:18:18.358 Rave[3923:340203] Background: >

Printing the color of the background:2014-11-26 15:23:13.467 Rave[3962:342332] Background Color: UIDeviceRGBColorSpace 0 1 1 1

Also the background color is being modified just not updated on screen of the simulator.

Answer 1

There are several things than could be wrong. You need to check several things, first the connection between storyboard (or Xib) and your viewController are Ok. A good things its make the connection with the background view all by code. (If you are adding another view inside de view in order to be the background delete it, If you are only a View in story is Ok).

Try this in your code:

- (IBAction)ButtonClick:(id)sender {

if(flag == 0){

    flag = 1;
    letterR.textColor = [UIColor blackColor];
    self.view.backgroundColor = [UIColor whiteColor];
    NSLog(@"With flag=0, this is firing, The UILable is:%@",[letteR description]);
 }

else if(flag == 1){

    flag = 0;
    letterR.textColor = [UIColor whiteColor];
    self.view.backgroundColor = [UIColor colorWithRed:0 green:1 blue:1 alpha:1];
    NSLog(@"With flag=1, this is firing, The UILable is:%@",[letteR description]);
}
}

You need to see than the UILabel exist.(And the answer is no null. Well, This is a start point, test this a comment for more help.