iOS TabBar Image assignment

问题

If it is possible, how would you go about setting a custom image to each state (selected/not selected) of tab bar items. This would need to override the default behavior which blues the tab bar item image when selected and grays it when not selected. Thanks.

回答1:

To recolor tab bar item use -

/* for colored tab items */

@interface UITabBar (ColorExtensions)
- (void)recolorItemsWithColor:(UIColor *)color shadowColor:(UIColor *)shadowColor shadowOffset:(CGSize)shadowOffset shadowBlur:(CGFloat)shadowBlur;
@end

@interface UITabBarItem (Private)
@property(retain, nonatomic) UIImage *selectedImage;
- (void)_updateView;
@end

@implementation UITabBar (ColorExtensions)

- (void)recolorItemsWithColor:(UIColor *)color shadowColor:(UIColor *)shadowColor shadowOffset:(CGSize)shadowOffset shadowBlur:(CGFloat)shadowBlur
{
    CGColorRef cgColor = [color CGColor];
    CGColorRef cgShadowColor = [shadowColor CGColor];
    for (UITabBarItem *item in [self items])
        if ([item respondsToSelector:@selector(selectedImage)] &&
            [item respondsToSelector:@selector(setSelectedImage:)] &&
            [item respondsToSelector:@selector(_updateView)])
        {
            CGRect contextRect;
            contextRect.origin.x = 0.0f;
            contextRect.origin.y = 0.0f;
            contextRect.size = [[item selectedImage] size];
            // Retrieve source image and begin image context
            UIImage *itemImage = [item image];
            CGSize itemImageSize = [itemImage size];
            CGPoint itemImagePosition; 
            itemImagePosition.x = ceilf((contextRect.size.width - itemImageSize.width) / 2);
            itemImagePosition.y = ceilf((contextRect.size.height - itemImageSize.height) / 2);
            UIGraphicsBeginImageContext(contextRect.size);
            CGContextRef c = UIGraphicsGetCurrentContext();
            // Setup shadow
            CGContextSetShadowWithColor(c, shadowOffset, shadowBlur, cgShadowColor);

            // Setup transparency layer and clip to mask
            CGContextBeginTransparencyLayer(c, NULL);
            CGContextScaleCTM(c, 1.0, -1.0);
            CGContextClipToMask(c, CGRectMake(itemImagePosition.x, -itemImagePosition.y, itemImageSize.width, -itemImageSize.height), [itemImage CGImage]);

        /*  //Setup the gradient... 
            CGFloat components[8] = {0.0,0.4,1.0,0.2,0.0,0.6,1.0,1.0};
            CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();  
            CGGradientRef colorGradient = CGGradientCreateWithColorComponents(colorSpace, components, NULL, 2);
            CGContextDrawLinearGradient(c, colorGradient,CGPointZero,CGPointMake(0,contextRect.size.height),0);
        */  

            // Fill and end the transparency layer
            CGContextSetFillColorWithColor(c, cgColor);
            contextRect.size.height = -contextRect.size.height;
            CGContextFillRect(c, contextRect);
            CGContextEndTransparencyLayer(c);



            // Set selected image and end context
            [item setSelectedImage:UIGraphicsGetImageFromCurrentImageContext()];
            UIGraphicsEndImageContext();
            // Update the view
            [item _updateView];



        }

}

@end


/* colored tab items code completed */

then in app delegate use -

[[tabbarcontroller tabBar] recolorItemsWithColor:[UIColor colorWithRed:0.6640 green:0.1992 blue:0.1992 alpha:1.0] shadowColor:[UIColor clearColor] shadowOffset:CGSizeMake(0.0f, -1.0f) shadowBlur:3.0f];

回答2:

Your question sounds like you are trying to change the selection colour of the tab bar. It's not easy but can be done. Here are some links to discussions about it

Custom colors in UITabBar

http://didikot.com/?p=106

A google search will bring up others if these don't help.

来源：https://stackoverflow.com/questions/5852112/ios-tabbar-image-assignment

标签

ios

uiimage

uitabbar