动态改变TabBar

UIImage+TabbarIcon.h

@interface UIImage (TabbarIcon)

/**
 BarItem.image
 @param imageUrl 图片链接
 @return image
 -------------------------------------
 nav.tabBarItem.image = [UIImage imageWithData:data];方式赋值,Xcode会把图片当成@1x,即图片多大tabBarItem就多大。
 所以，将图片存在本地，命名为@2x或@3x，imageWithContentsOfFile:方式进行赋值

 icon链接格式，例如：@"https://gitee.com/Ccfax/HunterPrivateImages/raw/master/navi_study@2x.png"最后以@2x，或@3x结尾。
 */
+ (UIImage *)barItemImage:(NSString *)imageUrl;

@end

UIImage+TabbarIcon.m

#import "UIImage+TabbarIcon.h"

@implementation UIImage (TabbarIcon)

+ (UIImage *)barItemImage:(NSString *)imageUrl{
    NSArray *stringArr = [imageUrl componentsSeparatedByString:@"/"];
    NSString *imageName = stringArr.lastObject;
    NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]];
    UIImage *image = [UIImage imageWithData:data];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory,NSUserDomainMask,YES);
    NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:imageName];
    // 判断文件是否已存在，存在，删除原文件
    if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
        [[NSFileManager defaultManager] removeItemAtPath:filePath error:nil];
    }
    // 将image写入沙河
    [UIImagePNGRepresentation(image) writeToFile:filePath atomically:YES];
    return [UIImage imageWithContentsOfFile:filePath];
}

@end