重写UIViewController方法 - (void)setTitle;
- (void)setTitle:(NSString *)title{
[super setTitle:title];
UIView *titleView=[[UIView alloc] init];
titleView.size = [title sizeWithAttributes:@{NSFontAttributeName : [UIFont systemFontOfSize:20]}];
self.navigationItem.titleView=titleView;
UILabel *titleL=[[UILabel alloc] init];
[titleView addSubview:titleL];
titleL.frame=titleView.bounds;
titleL.text=title;
titleL.textAlignment=NSTextAlignmentCenter;
titleL.font=[UIFont systemFontOfSize:20];
CAGradientLayer *gradientLayer=[CAGradientLayer layer];
gradientLayer.startPoint=CGPointMake(0, 0.2);
gradientLayer.endPoint=CGPointMake(0, 1);
gradientLayer.colors=@[(id)[UIColor redColor].CGColor, (id)[UIColor greenColor].CGColor];
[titleView.layer addSublayer:gradientLayer];
gradientLayer.frame=titleL.frame;
gradientLayer.mask=titleL.layer;
titleL.frame=gradientLayer.bounds;
}
