WordPress仅在侧边栏上显示第一个父级及其子菜单

Question

I have a main navigation and all parents have children.
Example:
Parent Page A:

• Child A1
  - Child A11
  - Child A12
  - Child A12
  - Child A13
  
• Child A2
• Child A3

Parent Page B:

• Child B1
  - Child B11
  - Child B12
  - Child B12
  - Child B13
  
• Child B2

If we are click on Child A12, sidebar should looks like:
Parent Page A:

• Child A1
  - Child A11
  - Child A12
  - Child A12
  - Child A13
  
• Child A2
• Child A3

Thanks.

Answer 1

I think you want to use vertical navigation menu like accordion, so look this to jquery simple vertical menu and on this base write your php code, also you can look on this example of php menu . When you will split this two examples I gues you will recieve that functionality that you want.

Answer 2

You should check out this plugin: http://wordpress.org/plugins/child-navigation/

It adds some arguments to wp_nav_menu()

This should do exactly what you want:

wp_nav_menu( array( 
    'theme_location' => 'my_menu_location',
    'children_only' => TRUE,
    'children_start_level' => 1,
    'children_show_start_level' => true,
) );