iphone - NavigationBar 图层渐变效果不佳

Question

我正在向导航栏层添加渐变，并且效果很好。当我推送另一个 View Controller 和弹出 View Controller 时，问题就来了。父 View Controller 有右边的条形按钮项目，当我弹出 View Controller 时，它的颜色会变暗。我的代码是

CGRect navFrame = self.navigationController.navigationBar.frame;
navFrame.origin.y = 0.0f;
[self.navigationController.navigationBar.layer insertSublayer:[AddGradient addGradientToNavigationBar:navFrame] atIndex:0];

addGradientToNavigationBar 的代码是

+ (CAGradientLayer*)addGradientToNavigationBar:(CGRect)navRect {

    CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.frame = navRect;
    gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0] CGColor],
                   (id)[[XAppDelegate getColor] CGColor], nil];

    return gradient;
}

Answer 1

我也遇到了同样的问题。我试图使用 UIBarStyleBlackTranslucent 样式将渐变层添加到导航栏以获得玻璃效果。在网上搜索和大量实验后，我还没有找到解决该问题的正确方法。最后我想出了以下解决方法:

    CAGradientLayer *yourGradient = ...

//需要两个额外的层来模仿 UIBarStyleBlackTranslucent 风格

    CAGradientLayer *gradient = [CAGradientLayer layer];

    gradient.frame = CGRectMake(0, 0, 320, 44);


    NSMutableArray *cgColors = [[NSMutableArray alloc] init];

    [cgColors addObject:(id)[[UIColor colorWithRed:0.0
                                     green:0.0
                                      blue:0.0
                                     alpha:0.2] CGColor]];
    [cgColors addObject:(id)[[UIColor colorWithRed:0.0
                                     green:0.0
                                      blue:0.0
                                     alpha:0.6] CGColor]];
    [cgColors addObject:(id)[[UIColor colorWithRed:0.0
                                     green:0.0
                                      blue:0.0
                                     alpha:0.5] CGColor]];

    gradient.colors = cgColors;

    CALayer *layer = [CALayer layer];

    _layer.frame = CGRectMake(0, 22, 320, 22);

    _layer.backgroundColor =[[UIColor colorWithRed:0.0
                                             green:0.0
                                              blue:0.0
                                             alpha:0.2] CGColor];

//导航栏按钮需要这个

    [rootController.navigationBar setBarStyle:UIBarStyleBlackTranslucent];

//在导航栏层的第一个子层添加层

    [[[rootController.navigationBar.layer sublayers] objectAtIndex:0] insertSublayer:yourGradient atIndex:0];

//添加渐变层后，UIBarStyleBlackTranslucent 样式效果消失

//来自栏(但不是来自按钮)

//所以需要下面的来模仿一下

    [[[rootController.navigationBar.layer sublayers] objectAtIndex:0] insertSublayer:gradient atIndex:1];

    [[[rootController.navigationBar.layer sublayers] objectAtIndex:0] insertSublayer:layer atIndex:2];

您可能还想为图层添加一些边框，因为边框似乎消失了。