動態修改UINavigationBar背景

問題: 改背景僅需在UINavigationBar的子視圖中加入UIImageView，但若是想在應用中修改背景又應該怎麼辦呢?

解決: 有些第三方的框架或者類都要派生UINavigationBar，它們有些「壞味道」!

絕妙解決: 咱們會建立一個UINavigationBar的類別，並在UIApplicationDelegate中建立一個UIImage屬性。

AppDelegate.h

@interface AppDelegate : NSObject
{
    UIImage *navImage;
    //其餘略
}

@property (nonatomic, retain) UIImage *navImage;
//其餘略

AppDelegate.m

@implementation AppDelegate;

@synthesize navImage;
//其餘略

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

    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

一旦完成了這些，就能夠按以下代碼改變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];
}

 

原文連接： http://iphonedevblog.com/code/dynamically-change-a-uinavigationbars-background/