动态修改UINavigationBar背景

问题: 改背景仅需在UINavigationBar的子视图中加入UIImageView，但若是想在应用中修改背景又应该怎么办呢?

解决: 有些第三方的框架或者类都要派生UINavigationBar，它们有些“坏味道”!

绝妙解决: 咱们会建立一个UINavigationBar的类别，并在UIApplicationDelegate中建立一个UIImage属性。

AppDelegate.h

@interface AppDelegate : NSObject
{
    UIImage *navImage;
    //其余略
}

@property (nonatomic, retain) UIImage *navImage;
//其余略

AppDelegate.m

@implementation AppDelegate;

@synthesize navImage;
//其余略

- (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:
(NSDictionary *)launchOptions
{
    self.navImage = [UIImage
    p_w_picpathNamed:@"navigation-bar-cooler.png"];
    //其余略

    return YES;
}

UINavigationBar (Helpers).h

@interface UINavigationBar (Helpers)

@end

UINavigationBar (Helpers).m

#import "AppDelegate.h"

#import "UINavigationBar (Helpers).h"

@implementation UINavigationBar (Helpers)

- (void)drawRect:(CGRect)rect
{
    AppDelegate *delegate = (AppDelegate *)
    [[UIApplication sharedApplication] delegate];
    [delegate.navImage drawInRect:
    CGRectMake(0, 0, self.frame.size.width,
    self.frame.size.height)];
}

@end

一旦完成了这些，就能够按以下代码改变UINavigationBar的背景了：

- (void)viewWillAppear:(BOOL)animated
{
    delegate.navImage = [UIImage p_w_picpathNamed:
    @"navigation-bar-other.png"];
    [self.navigationController.navigationBar
    setNeedsDisplay];

    [super viewWillAppear:animated];
}

 

原文连接： http://iphonedevblog.com/code/dynamically-change-a-uinavigationbars-background/