添加陰影UINavigationBar的底部只有

Question

我有以下代碼：

self.navigationBar_.layer.shadowColor = [UIColor blackColor].CGColor; 
      self.navigationBar_.layer.shadowOpacity = 0.3f; 
      self.navigationBar_.layer.shadowOffset = CGSizeMake(0.0f, 0.0f); 
      self.navigationBar_.layer.shadowRadius = 3.0f; 
      self.navigationBar_.layer.masksToBounds = NO; 

我基本上只希望邊框添加到底部，而不是整個矩形。我該怎麼做呢？上面的代碼也會爲左邊，右邊，上邊框添加陰影。

Answer 1

您可以使用漸變來代替圖層陰影。你可以使用透明的PNG漸變，但這裏是一個如何編程的例子：

UIView *topShadowView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.navigationBar.bounds.size.width, 10)]; 
CAGradientLayer *topShadow = [CAGradientLayer layer]; 
topShadow.frame = CGRectMake(0, 0, self.navigationBar.bounds.size.width, 10); 
topShadow.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithWhite:0.0 alpha:0.25f] CGColor], (id)[[UIColor clearColor] CGColor], nil]; 
[topShadowView.layer insertSublayer:topShadow atIndex:0]; 
[self.view addSubview:topShadowView];