Questions about the use of Viewpager and fragment in conjunction with the life cycle.

First of all, this blog post only explores a very small problem.

is the life cycle call problem when Viewpager and fragment are used together.

Let's draw a conclusion:

1. When the screen shows your nth fragment, your first (N-1) and (n+1) fragment will perform their life cycle to the onresume stage.

2. All fragment except for the above three fragment will not be called.

Here is the verification code:

First of all Is my mainactivity ()

public class Mainactivity extends fragmentactivity {Viewpager viewpager;    Arraylist<fragment> fragments;    String[] Strings=new string[]{"A", "B", "C", "D", "E"};        @Override protected void OnCreate (Bundle savedinstancestate) {super.oncreate (savedinstancestate);        Setcontentview (R.layout.activity_main);        Viewpager= (Viewpager) Findviewbyid (R.id.viewpager);        Fragments=new arraylist<fragment> ();        for (String s:strings) {fragments.add (new Fragmenta (s));        } Fragmentmanager Fm=getsupportfragmentmanager (); Fragmentpageradapter fragmentpageradapter=new fragmentpageradapter (FM) {@Override public Fragment ge            TItem (int position) {return fragments.get (position);            } @Override public int getcount () {return fragments.size ();        }        };        Viewpager.setadapter (Fragmentpageradapter);    Viewpager.setcurrentitem (1);}} 

Demo is simple, is dynamically based on the content of string[] to generate a group of fragment, and through the Viewpager to complete the load. Well, we first chose to load the second page, so that we could get a better idea of what fragment was called.

Next is the content of Fragmenta ().

public class Fragmenta extends Fragment {TextView TextView;    String s;        Public Fragmenta (String s) {super ();    This.s=s;        } @Override public void Onattach (context context) {Super.onattach (context);    LOG.E ("Test", "Onattach:" +s);        } @Override public void OnCreate (@Nullable Bundle savedinstancestate) {super.oncreate (savedinstancestate);    LOG.E ("Test", "OnCreate:" +s); } @Override Public View oncreateview (Layoutinflater inflater, @Nullable viewgroup container, @Nullable Bundle Savedi        Nstancestate) {View view=inflater.inflate (r.layout.frag_a,null);        textview= (TextView) View.findviewbyid (r.id.tv_frag_a);        LOG.E ("Test", "Oncreateview:" +s);    return view; } @Override public void onactivitycreated (@Nullable Bundle savedinstancestate) {super.onactivitycreated (save        Dinstancestate);    LOG.E ("Test", "onactivitycreated:" +s); } @Override public void OnStart () {super.onsTart ();    LOG.E ("Test", "OnStart ():" +s);        } @Override public void Onresume () {super.onresume ();        Textview.settext (s);    LOG.E ("Test", "Onresume:" +s); }

Next, let's look at what log will pass to us when the program starts.

05-08 13:43:56.540 14264-14264/com.example.chunya.testviewpager e/test:onattach:b05-08 13:43:56.540 14264-14264/ Com.example.chunya.testviewpager e/test:oncreate:b05-08 13:43:56.541 14264-14264/com.example.chunya.testviewpager e/test:onattach:c05-08 13:43:56.541 14264-14264/com.example.chunya.testviewpager e/test:oncreate:c05-08 13:43:56.544 14264-14264/com.example.chunya.testviewpager e/test:oncreateview:c05-08 13:43:56.545 14264-14264/ Com.example.chunya.testviewpager e/test:onactivitycreated:c05-08 13:43:56.546 14264-14264/ Com.example.chunya.testviewpager e/test:oncreateview:b05-08 13:43:56.546 14264-14264/ Com.example.chunya.testviewpager e/test:onactivitycreated:b05-08 13:43:56.546 14264-14264/ Com.example.chunya.testviewpager E/test:onstart (): b05-08 13:43:56.546 14264-14264/ Com.example.chunya.testviewpager e/test:onresume:b05-08 13:43:56.546 14264-14264/com.example.chunya.testviewpager e/test:onattach:a05-08 13:43:56.546 14264-14264/com.example.chunya.testviewpager E/Test: oncreate:a05-08 13:43:56.547 14264-14264/com.example.chunya.testviewpager e/test:oncreateview:a05-08 13:43:56.547 14264-14264/com.example.chunya.testviewpager e/test:onactivitycreated:a05-08 13:43:56.547 14264-14264/ Com.example.chunya.testviewpager E/test:onstart (): c05-08 13:43:56.548 14264-14264/ Com.example.chunya.testviewpager e/test:onresume:c05-08 13:43:56.548 14264-14264/com.example.chunya.testviewpager E/test:onstart (): a05-08 13:43:56.548 14264-14264/com.example.chunya.testviewpager e/test:onresume:a

Obviously, we chose the second page, then the load is "B", but A and C almost and B have finished loading the content at the same time.

The D and E pages are not loaded, but when the fragment slide, they will be loaded in succession.

Questions about the use of Viewpager and fragment in conjunction with the life cycle.