java - Android Fragment instantiation: newInstance() -

i read many articles , stackoverflow answers still cannot understand why need factory method create instance of fragment.

the following fragment classes both work fine.

fragment 2 constructors:

public class ctorfragment extends fragment {     private static final string key = "the_key";      public ctorfragment() {         // android calls default constructor default constructor must explicitly defined.         // have constructor, android won't create default constructor us.     }      public ctorfragment(string s) {         // set arguments.         bundle bundle = new bundle();         bundle.putstring(key, s);          setarguments(bundle);     }      @nullable     @override     public view oncreateview(layoutinflater inflater, @nullable viewgroup container, bundle savedinstancestate) {         view fragment = inflater.inflate(r.layout.fragment_my, container, false);         textview textview = (textview) fragment.findviewbyid(r.id.textview);          // use getarguments() string argument set constructor parameter.         textview.settext(getarguments().getstring(key));         return fragment;     } } 

fragment static factory method:

public class staticfragment extends fragment {     private static final string key = "the_key";      public static staticfragment newinstance(string s) {         staticfragment fragment = new staticfragment();         // set arguments.         bundle bundle = new bundle();         bundle.putstring(key, s);          fragment.setarguments(bundle);         return fragment;     }      @nullable     @override     public view oncreateview(layoutinflater inflater, @nullable viewgroup container, bundle savedinstancestate) {         view fragment = inflater.inflate(r.layout.fragment_my, container, false);         textview textview = (textview) fragment.findviewbyid(r.id.textview);          // use getarguments() string argument set constructor parameter.         textview.settext(getarguments().getstring(key));         return fragment;     } } 

can please explain why (including google) "strongly recommends" 1 static factory method? there critical me , others coming non-android background missing?

is have define 2 methods (constructors) instead of 1 (static factory method) causes fuss?

still cannot understand why need factory method create instance of fragment

"need" strong word. not "need" factory method. do need:

• a public zero-argument constructor, ideally empty; and

• an organized means set fragment, in way survives configuration changes

can please explain why (including google) "strongly recommends" 1 static factory method?

if have no explicit constructors on java class, automatically empty public zero-argument constructor, framework needs create fragment.

if create constructor takes arguments (e.g., ctorfragment(string s)), have remember create public zero-argument constructor (ctorfragment()). might remember this. many inexperienced programmers not.

writing factory method achieves same objective non-zero-arguments constructor, without clobbering automatically-created zero-argument constructor.

if experienced java programmer, , not factory methods, , can read stack traces , otherwise remember add public zero-argument constructor, welcome create additional constructors , use them.

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