iOS中Navbar設定漸層色效果

- (void) viewWillAppear:(BOOL)animated{    [super viewWillAppear:animated];    //狀態列高亮    self.navigationController.navigationBar.barStyle = UIStatusBarStyleLightContent;    //導航漸層色    CAGradientLayer *gradientLayer = [CAGradientLayer layer];    gradientLayer.colors = @[(__bridge id)[UIColor colorWithRed:255 green:70 blue:93 alpha:1].CGColor,(__bridge id)[UIColor colorWithRed:251 green:108 blue:42 alpha:1].CGColor];    gradientLayer.locations = @[@0.3, @1.0];    gradientLayer.startPoint = CGPointMake(0, 0);    gradientLayer.endPoint = CGPointMake(1.0, 0);    gradientLayer.frame = CGRectMake(0, -20, ScreenWidth, 64);    [self.navigationController.navigationBar.layer addSublayer:gradientLayer];}