android - Manage fragment life cycle with navigation drawer -

i have architectural issue in application . have used 1 activity navigation drawer , several fragments .now ,

suppose have 2 fragments , b . navigation structure somewhat:

a

   a1    a2 

b

   b1    b2 

where a1,a2 of type fragment , b1,b2 of type b fragment. difference between same type of fragments eg. a1,a2 of data .

my first approach :

whenever user click on a1,a2,b1,b2 . create new instance of type , replace fragment.

  fragment fragment =a.newinstance();   private void replacefragment(fragment fragment) {         fragmentmanager fragmentmanager = getsupportfragmentmanager();         fragmentmanager.begintransaction()                 .replace(r.id.content_frame, fragment).commit();         mdrawerlayout.closedrawer(rldrawer);     } 

note : not want add them stack.

later on realize approach inefficient every time crate new instance on fragment if of same type . said before difference in data .so, move next approach

second approach :

now activity has data member (references) of fragment , b . check if null create new instance else change data :

   if (a == null) {             = a.newinstance();         } else {             ((a) a).changedata();         }         replacefragment(a); 

problem approach when switch fragment a1 b1 a1 fragment destroyed reference remain activity . when switch b1 a1 not create new instance can see in above code @ same time oncreate() method gets called on fragment a.

should remove reference activity ondestroy() called on fragment ?

does second approach correct ?

is there better approach this?

thanks in advance.

i modify first approach.

use string tags fragment. when replacing fragment use replace method 3 parameters, example:

  fragmentmanager.begintransaction()                 .replace(r.id.content_frame, fragment, tag_a1).commit(); 

where tag_a1 unique string tag.

you can use method findfragmentbytag fragmentmanager check if fragment created before replace.

fragmentmanager fragmentmanager = getsupportfragmentmanager(); fragment fragmenta1 = fragmentmanager.findfragmentbytag(tag_a1); if(fragment == null) {     fragment = a.newinstance(); } fragmentmanager.begintransaction()                     .replace(r.id.content_frame, fragment, tag_a1).commit();