iOS 导航栏渐变

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{

if (scrollView==self.ActivityTableview) {

//        NSLog(@"%f",scrollView.contentOffset.y);

CGFloat offsetY = scrollView.contentOffset.y;

if (scrollView.contentOffset.y>=-20 && scrollView.contentOffset.y<50) {

[self.navigationController.navigationBar setBackgroundColor:[UIColor colorWithRed:255/255.0f green:255/255.0f  blue:255/255.0f  alpha:offsetY*2/100]];

[self.navigationController.navigationBar setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[UIColor whiteColor], NSForegroundColorAttributeName, nil]];

[self setStatusBarBackgroundColor:[UIColor colorWithRed:255/255.0f green:255/255.0f  blue:255/255.0f  alpha:offsetY*2/100]];

//NSLog(@"变色");

}else if (scrollView.contentOffset.y<-20){

[self.navigationController.navigationBar setBackgroundColor:[UIColor colorWithRed:226/255.0f green:67/255.0f  blue:70/255.0f  alpha:0.0]];

[self.navigationController.navigationBar setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[UIColor whiteColor], NSForegroundColorAttributeName, nil]];

[self setStatusBarBackgroundColor:[UIColor colorWithRed:226/255.0f green:67/255.0f  blue:70/255.0f  alpha:0.0]];

}else{

[self.navigationController.navigationBar setBackgroundColor:[UIColor whiteColor]];

//            [self.navigationController.navigationBar setTintColor:[UIColor blackColor]];

[self.navigationController.navigationBar setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[UIColor blackColor], NSForegroundColorAttributeName, nil]];

[self setStatusBarBackgroundColor:[UIColor whiteColor]];

}

}

}

- (void)setStatusBarBackgroundColor:(UIColor *)color {

UIView *statusBar = [[[UIApplication sharedApplication] valueForKey:@"statusBarWindow"] valueForKey:@"statusBar"];

if ([statusBar respondsToSelector:@selector(setBackgroundColor:)]) {

statusBar.backgroundColor = color;

}

}