导航栏全透明

方法一:

- (void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    [self.navigationController.navigationBar setBackgroundImage:[[UIImage alloc] init] forBarMetrics:UIBarMetricsDefault];
    [self.navigationController.navigationBar setShadowImage:[[UIImage alloc] init]];
}
- (void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    [self.navigationController.navigationBar setBackgroundImage:nil forBarMetrics:UIBarMetricsDefault];
   [self.navigationController.navigationBar setShadowImage:nil];
}

以上方法,发现有一个bug,在界面间进行push和pop时,导航栏会有闪现;

方法二:

这个设置就能解决上面的bug

- (void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    self.navigationController.navigationBar.translucent = YES;
    self.navigationController.navigationBar.subviews[0].alpha = 0.0;
}

- (void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    self.navigationController.navigationBar.translucent = NO;
    self.navigationController.navigationBar.subviews[0].alpha = 1.0;
//这个颜色的设置是为了填充上因为translucent导致的导航栏背景变成白色,如果你要的就是白色,这个可以忽略;
    [self.navigationController.navigationBar setBackgroundImage:[UIColor createImageWithColor:[UIColor initWithR:246 G:246 B:247]] forBarMetrics:UIBarMetricsDefault];
}

上面用到的一个颜色生成图片的方法:

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface UIColor (RGB)
#pragma mark 颜色转图片
+ (UIImage *)createImageWithColor:(UIColor*)color;
@end

+ (UIImage*)createImageWithColor:(UIColor*)color{
    
    CGRect rect=CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    
    UIGraphicsBeginImageContext(rect.size);
    
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    CGContextSetFillColorWithColor(context, [color CGColor]);
    
    CGContextFillRect(context, rect);
    
    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
    
    return theImage;
    
}