改变self.title的字体颜色、大小等

NSDictionary *dict = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:[UIColor colorWithRed:200 green:200 blue:200 alpha:1],[UIFont boldSystemFontOfSize:20.0f],[UIColor colorWithWhite:0.0 alpha:1], nil] forKeys:[NSArray arrayWithObjects:UITextAttributeTextColor,UITextAttributeFont,UITextAttributeTextShadowColor, nil]];
        self.navigationBar.titleTextAttributes = dict;