渐变导航栏初级版本：http://blog.csdn.net/codingfire/article/details/51604098
渐变导航栏升级版本：http://blog.csdn.net/codingfire/article/details/53705318
以上是博主写的渐变导航栏的进化之路，上一篇博客最后说明了升级版中的bug，在这一版中对这一bug进行了修复，其实很简单，就是增加了一个新的变量来给一个全局的透明度，在上下滚动时改变这个全局的透明度，然后判断透明度的边界，下面来看看代码吧：
- (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. self.view.backgroundColor=[UIColor whiteColor]; lhAlpha = 1; } - (void)scrollViewDidScroll:(UIScrollView *)scrollView{ currentPostion = scrollView.contentOffset.y; if (currentPostion > 0) { if (currentPostion - _lastPosition >= 0) { if ([[NSUserDefaults standardUserDefaults]objectForKey:@"first"]!=nil) { [[NSUserDefaults standardUserDefaults]removeObjectForKey:@"first"]; [[NSUserDefaults standardUserDefaults]synchronize]; // [NSObject cancelPreviousPerformRequestsWithTarget:self]; // [self performSelector:@selector(scrollViewDidEndScrollingAnimation:) withObject:nil afterDelay:0.00001]; [[NSUserDefaults standardUserDefaults]setObject:@"1" forKey:@"second"]; [[NSUserDefaults standardUserDefaults]synchronize]; stopPosition = currentPostion + 64; } _lastPosition = currentPostion; NSLog(@"ScrollUp now current:%f last:%f stop:%f",currentPostion,_lastPosition,stopPosition); if (lhAlpha >= 0) { lhAlpha = lhAlpha - 0.025f; } else { lhAlpha = 0; } self.navigationController.navigationBar.alpha = lhAlpha; // self.navigationController.navigationBar.alpha = 1 - currentPostion / 400; } else { if ([[NSUserDefaults standardUserDefaults]objectForKey:@"second"]!=nil) { [[NSUserDefaults standardUserDefaults]removeObjectForKey:@"second"]; [[NSUserDefaults standardUserDefaults]synchronize]; // [NSObject cancelPreviousPerformRequestsWithTarget:self]; // [self performSelector:@selector(scrollViewDidEndScrollingAnimation:) withObject:nil afterDelay:0.00001]; [[NSUserDefaults standardUserDefaults]setObject:@"1" forKey:@"first"]; [[NSUserDefaults standardUserDefaults]synchronize]; stopPosition = currentPostion + 64; } _lastPosition = currentPostion; NSLog(@"ScrollDown now current:%f last:%f stop:%f",currentPostion,_lastPosition,stopPosition); if (lhAlpha <= 1) { //这里的0.025自己可以调整，有的上下滚动透明度变化一个快一个慢，切记不要让向下的小于向上的，否则滚动到顶端导航栏是透明的 lhAlpha = lhAlpha + 0.025f; } else { lhAlpha = 1; } self.navigationController.navigationBar.alpha = lhAlpha; // self.navigationController.navigationBar.alpha = (stopPosition - currentPostion)/200; } } }
Demo的下载地址：下载地址
建议先看一下前面两篇，这样会增加理解，实现不难，主要是一个思路。
