源代码

链接:
https://pan.baidu.com/s/16XRHhx0LS_qgZ8FAUjNXkQ 密码:sooq

主要代码：

//
//  ViewController.m
//  主题切换
//
//  Created by 许磊 on 2019/2/26.
//  Copyright © 2019年 xulei. All rights reserved.
//

#import "ViewController.h"
#import "ThemeManager.h"
#import "ThemeImageView.h"
#import "Constants.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    //布局
    [self UIInit];
}

-(void)UIInit{
    
    //创建图片1
    ThemeImageView *v1 = [[ThemeImageView alloc] initWithFrame:CGRectMake(self.view.frame.size.width/2-50, 200, 100, 50)];
    v1.imageName = @"1.png";
    [self.view addSubview:v1];
    
    //创建图片1
    ThemeImageView *v2 = [[ThemeImageView alloc] initWithFrame:CGRectMake(self.view.frame.size.width/2-50, 300, 100, 50)];
    v2.imageName = @"2.png";
    [self.view addSubview:v2];
    
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    //切换主题
    
    //获取触摸点的坐标
    UITouch *touch = [touches anyObject];
    CGPoint location = [touch locationInView:self.view];
    
    if (location.x > self.view.center.x) {
        //1.改变Thememanager里面的themeName
        [ThemeManager sharedInstance].themeName = @"黑色";
    } else {
        //2.改变Thememanager里面的themeName
        [ThemeManager sharedInstance].themeName = @"蓝色";
    }
    
    //3.发通知
    [[NSNotificationCenter defaultCenter] postNotificationName:kThemeDidChangeNotificationName object:nil];
}

@end

//
//  Constants.h
//  主题切换
//
//  Created by 许磊 on 2019/2/27.
//  Copyright © 2019年 xulei. All rights reserved.
//

#ifndef Constants_h
#define Constants_h

/**主题切换的消息名*/
#define kThemeDidChangeNotificationName @"kThemeDidChangeNotificationName"

#endif /* Constants_h */

//
//  ThemeManger.h
//  主题切换
//
//  Created by 许磊 on 2019/2/27.
//  Copyright © 2019年 xulei. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface ThemeManager : NSObject

/**记录当前的主题*/
@property (nonatomic,strong) NSString *themeName;

/** 获取某张图片在当前主题下对应的图片*/
-(UIImage *)getThemeImage:(NSString *)imageName;

/**提供类方法 快速获取一个对象 保证只有一个*/
+(ThemeManager *)sharedInstance;

@end

//
//  ThemeManger.m
//  主题切换
//
//  Created by 许磊 on 2019/2/27.
//  Copyright © 2019年 xulei. All rights reserved.
//

#import "ThemeManager.h"

static ThemeManager *instance = nil;

@implementation ThemeManager

#pragma mark -------shareInstance ---------
//单例模式
+(ThemeManager *)sharedInstance{
    
    if (instance == nil) {
        
        instance = [[ThemeManager alloc] init];
        
        //提供一个默认的
        instance.themeName = @"粉色";
    }
    return instance;
}

#pragma mark -------getThemeImage: ---------
//获得图片
-(UIImage *)getThemeImage:(NSString *)imageName{
    
    //图片的路径 程序的根路径/theme/主题/imageName
    
    //1.获取程序的根路径
    NSString *path = [[NSBundle mainBundle] resourcePath];
    
    //2.拼接路径
    NSString *imagePath = [NSString stringWithFormat:@"%@/theme/%@/%@",path,self.themeName,imageName];
    NSLog(@"%@",imagePath);
    
    //3.获取图片
    UIImage *img = [UIImage imageWithContentsOfFile:imagePath];
    
    return img;
}


@end

//
//  ThemeImageView.h
//  主题切换
//
//  Created by 许磊 on 2019/2/27.
//  Copyright © 2019年 xulei. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface ThemeImageView : UIImageView

/**记录需要图片的名称*/
@property (nonatomic,strong) NSString *imageName;

@end

//
//  ThemeImageView.m
//  主题切换
//
//  Created by 许磊 on 2019/2/27.
//  Copyright © 2019年 xulei. All rights reserved.
//

#import "ThemeImageView.h"
#import "ThemeManager.h"
#import "Constants.h"

@implementation ThemeImageView

- (instancetype)initWithFrame:(CGRect)frame{
    self = [super initWithFrame:frame];
    if (self != nil){
        //监听消息
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(loadImage) name:kThemeDidChangeNotificationName object:nil];
    }
    return self;
}

//重写imageName的set方法
-(void)setImageName:(NSString *)imageName{
    
    _imageName = imageName;
    
    [self loadImage];
}

#pragma mark -------loadImage ---------
//加载图片
-(void)loadImage{
    
    //向ThemeManger获取对应主题的图片
    UIImage *img = [[ThemeManager sharedInstance] getThemeImage:self.imageName];
    
    //改变显示的图片
    self.image = img;
    
}

@end

//
//  ThemeNavigationController.h
//  主题切换
//
//  Created by 许磊 on 2019/2/27.
//  Copyright © 2019年 xulei. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface ThemeNavigationController : UINavigationController

/**记录需要图片的名称*/
@property (nonatomic,strong) NSString *imageName;

@end

//
//  ThemeNavigationController.m
//  主题切换
//
//  Created by 许磊 on 2019/2/27.
//  Copyright © 2019年 xulei. All rights reserved.
//

#import "ThemeNavigationController.h"
#import "ThemeManager.h"
#import "Constants.h"

@interface ThemeNavigationController ()

@end

@implementation ThemeNavigationController

- (void)viewDidLoad {
    [super viewDidLoad];
  
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(loadImage) name:kThemeDidChangeNotificationName object:nil];
    
    self.imageName = @"1.png";
    
}

//重写imageName的set方法
-(void)setImageName:(NSString *)imageName{
    
    _imageName = imageName;
    
    [self loadImage];
}

#pragma mark -------loadImage ---------
//加载图片
-(void)loadImage{
    
    //向ThemeManger获取对应主题的图片
    UIImage *img = [[ThemeManager sharedInstance] getThemeImage:self.imageName];
    
    [self.navigationBar setBackgroundImage:img forBarMetrics:UIBarMetricsDefault];
    
}


@end

运行结果

运行结果

附一：传递消息-消息通知

1.消息通知的优点是可以一对多进行消息传递，可以隔层传递
2.当发送消息时，注册的观察者就会收到消息执行对应的方法
3.观察者不会自动移除，需要手动移除

附二：视图与视图控制器搭建联系

示意图