以下方法可用來設置導航欄上的漸變色。

- (void)setNavigationBarBackgroundColor{

    //  創建 UIView用來承載漸變色放置在導航欄上時需要上移20否則狀態欄會露出

    UIView *myTopView = [[UIView alloc]initWithFrame:CGRectMake(0, -20,WIDTH ,64)];

//1、window 沒有設置導航控制器為根視圖的情況下

#if 0 

[self.view addSubview:myTopView];

//2、設置了導航控制器為根視圖。在AppDelegate中設置了

    self.window = [[UIWindow alloc]initWithFrame:[UIScreen mainScreen].bounds];

    self.window.rootViewController = [[UINavigationController alloc]initWithRootViewController:[ViewController new]];

    self.window.backgroundColor = [UIColor whiteColor];

    [self.window makeKeyAndVisible];

#else  //則視圖添加在navigationBar上 或者其他方法設置在navigationBar處

    [self.navigationController.navigationBar addSubview:myTopView];

#endif

    // 創建漸變色圖層

    CAGradientLayer *gradientLayer= [CAGradientLayer layer];

    gradientLayer.frame       =CGRectMake(0,0,WIDTH,64);

    gradientLayer.colors =@[

                             (id)[UIColor yellowColor].CGColor,

                             (id)[UIColor cyanColor].CGColor

                             ];

    /* The start and end points of the gradient when drawn into the layer's

     * coordinate space. The start point corresponds to the first gradient

     * stop, the end point to the last gradient stop. Both points are

     * defined in a unit coordinate space that is then mapped to the

     * layer's bounds rectangle when drawn. (I.e. [0,0] is the bottom-left

     * corner of the layer, [1,1] is the top-right corner.) The default values

     * are [.5,0] and [.5,1] respectively. Both are animatable.

     */

    // 設置漸變方向(0~1)默認位置為 (0.5,0) 和 (0.5,1)

    gradientLayer.startPoint =CGPointMake(0,0);

    gradientLayer.endPoint =CGPointMake(0,1);

    // 設置漸變色的起始位置和終止位置(顏色的分割點)

    /* An optional array of NSNumber objects defining the location of each

     * gradient stop as a value in the range [0,1]. The values must be

     * monotonically increasing. If a nil array is given, the stops are

     * assumed to sPRead uniformly across the [0,1] range. When rendered,

     * the colors are mapped to the output colorspace before being

     * interpolated. Defaults to nil. Animatable. */

    gradientLayer.locations =@[@(0.15f),@(0.98f)];

    //漸變色圖層的線寬

    gradientLayer.borderWidth  =0.0;

    // 添加圖層

    [myTopView.layer addSublayer:gradientLayer];

}