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Changing background color in UIView

I have a problem with setting the background color UIView

. I am using the following code:

self.view.backgroundColor = [UIColor colorWithRed:0 
                                            green:0.675 
                                             blue:0.929 
                                            alpha:1];

This works great when I set the background color right at the start of the app, but when I want to update my background color after I launch the app from the notification center widget it doesn't change color.

EDIT - A few more details:

When the app is launched from the Action Center, the AppDelegate method is called, which stores the called URL scheme as "NSString" and calls another method where the background color needs to be updated.

I have verified that the method call is working fine.

My problem is that the color is not being updated even though the method is being called.

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3 answers


I fixed my problem. In AppDelegate.m, in the method where I got the url that the application was launched with, I initialized a new ViewController instead of the old one that caused all my errors. Thank you for your help!



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if you launch the app from the action center it means the app goes from background to foreground. In this case you need to handle the uiview background in the applicationDidEnter background and applicationDidEnterForeground methods



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Update the color in the viewWillAppear

controller where your view is displayed. Set a breakpoint to make sure the code is called and the reference view is not nil

.

If you just want to "preserve" the color without displaying it, use NSUserDefaults

. You can only store primitives so you can do this for example.

// save
[[NSUserDefaults standardUserDefaults] setObject:@"0,0.675,0.929" forKey@"savedColor"];

// retrieve
NSString *colorString = [[NSUserDefaults standardUserDefaults] objectForKey:@"savedColor"];
NSArray *c = [colorString componentsSeparatedByString:@","];
CGFloat r = [c[0] floatValue];
CGFloat g = [c[1] floatValue];
CGFloat b = [c[2] floatValue];
UIColor *color = [UIColor colorWithRed:r green:g blue:b alpha:1];

Or maybe clearer and more succinct

// save
[[NSUserDefaults standardUserDefaults] setObject:
  @{@"red" : @0, @"green" : @0.675, @"blue" : @0.929} forKey:@"savedColor"];

// retrieve
NSDictionary *c = [[NSUserDefaults standardUserDefaults] objectForKey@"savedColor"];
UIColor *color = [UIColor 
   colorWithRed:c[@"red"]  green:c[@"green"] blue:c[@"blue"] alpha:1];

Now, you will apply all of this into convenience methods:

-(void)saveColorToUserDefaults:(UIColor*)color withKey:(NSString*)key {
    CGFloat red, green, blue, alpha;
    [color getRed:&red green:&green blue:&blue alpha:&alpha];
    [[NSUserDefaults standardUserDefaults] setObject:
       @{@"red": @(red), @"green" : @(green), @"blue" : @(blue), @"alpha" : @(alpha)}
       forKey: key];
}

-(UIColor*)colorFromUserDefaultsWithKey:(NSString *)key {
   NSDictionary *c = [[NSUserDefaults standardUserDefaults] objectForKey@"savedColor"];
   return = [UIColor colorWithRed:c[@"red"]  green:c[@"green"] 
                             blue:c[@"blue"] alpha:c[@"alpha"]];
}
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