在ios5之前的系統中,可以通過定義導覽列類别的方式自定義導覽列:
@implementation UINavigationBar (CustomImage)
- (void)drawRect:(CGRect)rect {
// Drawing code
UIImage *image = [[UIImage imageNamed:@"header.png"] retain];
[image drawInRect:CGRectMake(0, 0,self.frame.size.width , self.frame.size.height)];
[image release];
}
@end
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但在ios5中,這種方式不起作用了。詳見ios 5.0釋出說明:
http://developer.apple.com/library/ios/#releasenotes/General/RN-iOSSDK-5_0/_index.html#//apple_ref/doc/uid/TP40010949
在iOS 5中,UINavigationBar, UIToolbar, and UITabBar 的實作方式改變了,是以drawRect:方法不會被調用了。除非在他們的子類中實作。
是以,要在iOS 5.0中繼續使用自定義的導覽列,這裡提供兩種方法:
1、使用5.0中新提供的UINavigationBar的方法setBackgroundImage:forBarMetrics:來設定背景。
但是為了與4.0等系統相容,在使用該方法前必須先進行判斷:(在5.0之前的系統中繼續使用原來的方法)
(需要在每個用到navigationbar的地方都調用該方法,可能改動的地方比較多)
1 UINavigationBar *navBar = [myNavController navigationBar];
2 if ([navBar respondsToSelector:@selector(setBackgroundImage:forBarMetrics:)])
3 {
4 // set globablly for all UINavBars
5 [[UINavigationBar appearance] setBackgroundImage:[UIImage imageNamed:@"brnlthr_nav.jpg"] forBarMetrics:UIBarMetricsDefault];
6 // ...
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2、使用UINavigationBar的子類的方式來實作:(用這種方式可以不用對每個使用navigationbar的地方都進行修改,屬于懶人做法)
@interface MyNavigationBar : UINavigationBar
@end
@implementation MyNavigationBar
- (void)drawRect:(CGRect)rect {
[super drawRect:rect];
}
@end
@implementation UINavigationBar (LazyNavigationBar)
+ (Class)class {
return NSClassFromString(@"MyNavigationBar");
}
-(void)drawRect:(CGRect)rect {
UIImage *backImage = [UIImage imageNamed:@"backNav.png"];
[backImage drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
}
@end
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3.使用category 範疇 來實作
@implementationUINavigationBar(MyCustomNavBar)
-(void)setBackgroudImage:(UIImage*)image
{
CGSize imageSize =[image size];
self.frame =CGRectMake(self.frame.origin.x,self.frame.origin.y,self.frame.size.width, imageSize.height);
UIImageView*backgroundImage =[[UIImageView alloc] initWithImage:image];
backgroundImage.frame =self.bounds;
[self addSubview:backgroundImage];
[backgroundImage release];
}
@end
//The above swizzling will allow you to set any custom background image for the UINavigationBar(iOS5 & iOS4).
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Here's a less-ugly solution that works for both iOS4 and 5:
@implementationUINavigationBar(CustomBackground)
-(UIImage*)barBackground
{
return[UIImage imageNamed:@"top-navigation-bar.png"];
}
-(void)didMoveToSuperview
{
//iOS5 only
if([self respondsToSelector:@selector(setBackgroundImage:forBarMetrics:)])
{
[self setBackgroundImage:[self barBackground] forBarMetrics:UIBarMetricsDefault];
}
}
//this doesn't work on iOS5 but is needed for iOS4 and earlier
-(void)drawRect:(CGRect)rect
{
//draw image
[[self barBackground] drawInRect:rect];
}
@end
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