如何从UISearchBar移动占位符标签

我已经创建了一个简单的扩展UISearchBar，它比本机小一点。我已经实现了这个代码：如何从UISearchBar移动占位符标签

- (void)layoutSubviews{ 
    [super layoutSubviews]; 

    CGRect frame = self.frame; 
    if (frame.size.height != 32) { 
     frame.size.height = 32; 
     self.frame = frame; 
    } 

    [[UITextField appearanceWhenContainedIn:[UISearchBar class], nil] setDefaultTextAttributes:@{NSForegroundColorAttributeName:[UIColor colorWithHexString:@"#636363"]}]; 
    UITextField *searchTextField = [self valueForKey:@"_searchField"]; 
    UILabel *placeholderLabel = [searchTextField valueForKey:@"_placeholderLabel"]; 

    placeholderLabel.frame = CGRectMake(placeholderLabel.frame.origin.x , placeholderLabel.frame.origin.y + 8 , placeholderLabel.frame.size.width , placeholderLabel.frame.size.height); 
    [placeholderLabel setBackgroundColor:[UIColor redColor]]; 
    [placeholderLabel setFont:[UIFont systemFontOfSize:13]]; 

    [[UILabel appearanceWhenContainedIn:[UISearchBar class], nil] setTextColor:[UIColor colorWithHexString:@"#c6c6c6"]]; 

    self.layer.borderWidth = 1; 
    self.layer.borderColor = [[UIColor colorWithHexString:@"#949494"] CGColor]; 

    [self.layer setMasksToBounds:YES]; 
    [self.layer setCornerRadius:5]; 


}

但结果是这样的：