在UITabBar背景中设置渐变

Question

What is the easiest way that I can achieve something like this:

Is it through subclassing a UITabBarController? If yes what property needs to be changed?

Answer 1

This is an old question but it comes up first in a search for TabBar gradients. A far easier way to do this is with appearances. Just put this in your applicationDidFinishLaunching method.

[[UITabBar appearance] setBackgroundImage:[UIImage imageNamed:@"navBarImage_1x49"]];

And, as a bonus, if you prefer to create a gradient image in code, you can do this:

CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = CGRectMake(0, 0, 1, 49);
gradient.colors = [NSArray arrayWithObjects:(id)[UIColor.darkGrayColor] CGColor], (id)[UIColor.blackColor] CGColor], nil];
UIGraphicsBeginImageContext(gradient.frame.size);
CGContextRef context = UIGraphicsGetCurrentContext();
[gradient renderInContext:context];
UIImage *gradientImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Answer 2

I had the same problem with my app and I came up with following: in applicationDidFinishLaunching method I created a function to draw a gradient and used an instance of my UITabBarController to set up a correct gradient frame depending on the width of the device.

- (UIImage *)drawGradientInView:(UITabBarController *) tabBarVC {
    CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = CGRectMake(CGRectGetMinX(tabBarVC.tabBar.frame), CGRectGetMinY(tabBarVC.tabBar.frame), CGRectGetWidth(tabBarVC.view.frame), CGRectGetHeight(tabBarVC.tabBar.frame));

    //set up your gradient
    //......

    UIImage *gradientImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return gradientImage;
}

get the instance of UITabBarController

UITabBarController *tabVC = (UITabBarController *)[UIApplication sharedApplication].windows.firstObject.rootViewController;

set your gradient

[UITabBar appearance].backgroundImage = [self drawGradientInView:tabVC];

I'm not sure if that's a correct approach but it did work for me.

Answer 3

@interface UITabBarController (private)
- (UITabBar *)tabBar;
@end

@implementation CustomizeUITabBarController


- (void)viewDidLoad {
    [super viewDidLoad];

    CGRect frame = CGRectMake(0.0, 0.0, self.view.bounds.size.width, 48);
    UIView *v = [[UIView alloc] initWithFrame:frame];
    [v setBackgroundColor:kMainColor];
    [v setAlpha:0.5];
    [[self tabBar] addSubview:v];
    [v release];

}
@end

Hope it will help you....

Answer 4

Yes, subclassing an UITabbarController is the right way to do this.

Overwrite the drawRect method:

- (void)drawRect:(CGRect)rect {
    [[UIImage imageNamed:@"yourNavigationBar.png"] drawInRect: CGRectMake(0, 0, self.frame.size.width, self.frame.size.height) ];
}

And add the image with gradient into your project.